New scientist 9 4 2016

frozen black holes

The answers to everything lie close to absolute zero

where’s polly?

Helping the world’s shyest parrot find love

total recall

The odd minds of the people who can’t forget WEEKLY 9 April 2016

NEW Genes for old DNA fix promises new era of medicine SPECIAL REPORT

migration

The evolutionary roots of today’s crisis – and how we can use them to solve it

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Believing is seeing How your brain really senses the world

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Contents

Volume 230 No 3068

This issue online newscientist.com/issue/3068

Leader

News

5

8

Gene therapy gets approval for “bubble kids” in world first

News KLAUS GULDBRANDSEN/SCIENCE PHOTO LIBRARY

New genes for old

6 UPFRONT Inflatable hotel launches to ISS. Global obesity crisis revealed. Hunting ancient aliens.

Giant mine threatens Great Barrier Reef 8 THIS WEEK Planet Nine could be a stolen exoplanet.

The odd minds of people who can’t forget.

Did human sacrifice shape our society?

Saving the world’s weirdest parrot.

14 IN BRIEF Cloud atlas predicts species. Fizzy seas on Titan. Mosquito chemical weapons.

Caribou’s catch-22. Climate change’s bird winners. Mars dust devils

On the cover

29

38 Frozen black holes Absolute zero and the answer to everything 12 Where’s Polly?

Saving our shyest parrot 10 Total recall People who can’t forget 8 New genes for old DNA fix changes medicine 42 Believing is seeing

How your brain really

senses the world

Special report: Migration The evolutionary roots of today’s crisis – and how to solve it

Cover image Simon Pemberton

Analysis 16 Drugs reform Is the global war starting to fizzle out?

18 comment Climate change is boosting carb content of food. DNA technology helps to identify Bosnia’s fallen 19 INSIGHT Doctors are failing trans people

Technology 20 Teaching robots to see like we do.

Programmable cells. Bots infiltrate the insect world. Smartphone data to tackle dengue

Aperture

Features

24 Shadows at the dawn of photography

38

Opinion 26 Supercoral vs climate change Ruth Gates is creating corals tough enough to survive

Frozen black holes

Features

Jan Kornstaedt/Gallerystock

The answers to everything lie close to absolute zero

need an enlightened response to We migration based on evidence not prejudice

29 Migration (see above left) 38 Frozen black holes (see left)

CultureLab

Coming next week…

In sync

Take charge of your myriad body clocks

Cloud control

42 Predictive powers How our brains make models of reality 44 Smart cities Let’s leave them to sprawl 45 Sign of three Hunting an elusive symbol

Regulars 52 letters How I became a cancer drug fan 56 Feedback The sun is hollow, not 57 The Last Word Long in the tooth

Microbes that hijack the weather

9 April 2016 | NewScientist | 3

Marko Djurica/Reuters

LEADER

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by Williams Gibbons (Wolverhampton)

Move with the times Migration calls for an international, enlightened response VOWING to tighten borders has chunks of the world, from become a vote-winner around standardised internet protocols the world. With memories still and transnational payment fresh of the murderous attacks in systems to free trade agreements.

Paris and Brussels, calls to clamp But while enormous efforts down on migration have struck have been made to permit free a popular chord across Europe. movement of goods and services Hostility to migration is an and capital, the third leg of the animating force for many who economic triad, labour, remains want the UK to leave the European highly restricted under a Union. Australia has taken a patchwork of national controls. hard line and Donald Trump This leads to absurdities. has exploited simmering tensions Industrialised countries with in the US – a country built by the huge demographic challenges and world’s “huddled masses yearning consequent labour shortages are to breathe free”. “ Humanity has been on Terrorism and economic the move for millennia insecurity are genuine problems, and migration has made but hostility to immigrants is us what we are today” precisely the wrong response to them. If you look at the blocked from letting in foreigners evidence – and there is plenty to desperate for jobs. That is because look at – it is clear that clamping voters, often spurred on by down on immigration will not politicians capitalising on fear solve the problems that its and ignorance, think immigrants opponents want to solve. Quite the opposite, in fact (see page 29). will steal their jobs, drive down Migration is part of what we are their pay and hijack their social security. Yet none of that is true. as a species. Humanity has been Immigrants expand economies, on the move for millennia and it innovation and prosperity. is no exaggeration to say that it However, few in power are has made us what we are today: an increasingly globalised society prepared to acknowledge this.

The UK government, for example, in which communication and has vowed to slash immigration transport make it simple – in principle – to cross borders. Much and balance the books. It cannot of our economy and governance is do both at once. Its own advisers say that avoiding a budget deficit shared across increasingly large

requires an influx of young, hard-working and tax-paying immigrants.

Even if the economic case is clear, however, there is another factor fuelling hostility to immigration: tribalism.

People accustomed to cultural uniformity fear the arrival of incomers who are different.

Some of that fear derives from our evolutionary past: we are biologically primed to mistrust those we perceive as “other”.

But the long, albeit complicated, history of cultural mixing demonstrates that this need not prevent peaceful coexistence.

That does not mean migration should be left to work itself out – although over time it often does.

Nor should it be left to national governments on their own.

An intergovernmental agency that can collect the relevant data, promote research and formulate global rules is long overdue. Such a body would help governments make and defend evidence-based decisions about sharing our planet’s human resources.

Like it or not, migration is a fact of life and politicians are powerless to stop it. The only question is: do we want to manage it using the best available evidence, or run the world on the basis of ignorant, insular tribalism? n 9 April 2016 | NewScientist | 5

TOM JEFFERSON/GREENPEACE

UPFRONT

Green light for giant mine TO DIG or not to dig? The Queensland

the reef, damaging its ecosystem.

government has issued controversial licences for the development of a coal mine that would be Australia’s largest once completed. But conservationists are fighting the plan, which they say will be a disaster for the Great Barrier Reef.

Issued on Sunday, the three licences would permit the India-based company Adani to extract coal from the planned Carmichael coal mine in the Galilee Basin, one of the world’s largest untapped coal reserves, in

What’s more, mining the coal and burning it will generate huge amounts of carbon dioxide that will accelerate global warming and affect the health of the reef.

“If it goes ahead, burning coal from the Carmichael mine would create billions of tonnes of pollution, making climate change worse and irreversibly damaging the reef,” says Josh Meadows of the Australian Conservation Foundation, which is challenging the legality of previous

the heart of Queensland.

As part of the plan, which would see huge exports of coal to India, the port at Abbot Point (pictured) adjacent to the Great Barrier Reef would be expanded. This would potentially release plumes of soil and debris over

federal-level approval for the mine in a Brisbane court in May. “We will argue that the federal environment minister, Greg Hunt, did not properly consider the impact that pollution from burning the coal will have on the Great Barrier Reef,” he says.

A weighty world

(The Lancet, doi.org/bd2d).

About a fifth of all obese adults are in six rich, English-speaking countries – Australia, Canada, Ireland, New Zealand, the UK and the US. Some 50 million severely obese people also live here.

Island nations in Polynesia and Micronesia have the highest average body mass index. TimorLeste, Eritrea and Ethiopia have the lowest.

By 2025, the World Health Organization wants to reduce global obesity rates to their 2010 levels. The report suggests this will be no easy task.

–More industry, less reef –

Royalty-free drugs

anticancer drugs. “Companies, such as Roche, Novartis, Bayer, Astellas and BMS, with important oncology drugs, should begin to engage on expanding access to their patented medicines”, it said.

Of five major multinationals contacted by New Scientist, only Pfizer had responded by the time we went to press. “We are committed to providing broad access to our medicines through a variety of ways including partnerships, flexible access arrangements, and in certain less developed countries, donations,” a spokesperson said.

POOR countries will soon be able to make their own versions of GlaxoSmithKline’s drugs without paying royalties, the UK-based pharma giant has announced.

GSK said it will not file patents

for its drugs in countries deemed to be low income and least developed. In lower middle income countries, it will offer 10‑year licenses on generous terms to firms seeking to make generic copies of its drugs. It will also explore putting its experimental anticancer drug patents into a UN-backed “patent pool” so that the drugs can be made available cheaply to certain countries if and when they are approved.

Knowledge Ecology International, a non-governmental organisation in Washington DC, described the move as welcome and impressive. It urged others to follow GSK’s lead, especially with 6 | NewScientist | 9 April 2016

BIGELOW AEROSPACE

“GSK’s move is welcome but other companies should begin to expand access to patented medicines”

WE’RE getting fatter. The number of people who are classified as obese has rocketed from 105 million in 1975 to 641 million in 2014, according to an analysis of data from 196 million people in 186 countries.

“The world has transitioned from an era when underweight prevalence was more than double that of obesity, to one in which more people are obese than underweight,” team member Majid Ezzati of Imperial College London wrote in the report

Blow-up spacecraft THE International Space Station is about to get a new room – but first the crew will have to blow it up.

The Bigelow Expandable Activity Module (BEAM) will be carried to orbit folded inside a SpaceX cargo capsule, set to launch on 8 April. Unlike the rest of the ISS, which is aluminium, it is made from a top-secret soft and foldable fabric that still holds up to the harshness of space. It is –Puffed up new digs– designed to inflate in orbit, using

For new stories every day, visit newscientist.com/news

Planes, ships, CO2

extra air stored in internal tanks.

Bigelow launched smaller, stand-alone modules in 2006 and 2007, but this will be the first to attach to the ISS, allowing humans to try out these new digs.

Because the technology is still being tested, astronauts won’t occupy BEAM full time. If all goes to plan, the module will stay on the station for two years, allowing Bigelow and NASA to confirm it is able to resist the micrometeoroids that occasionally hit the ISS, maintain the correct temperature and resist radiation. If it works, Bigelow hopes to one day build a “space hotel” for tourists.

WILL the last great untamed carbon dioxide emitters – aviation and shipping – finally be brought under international control?

Last December’s Paris deal on climate change agreed national limits on emissions from power generation, land transport and deforestation from 2020. But it left untouched fast-rising emissions from aircraft and shipping. Meetings being held this month could change that.

The aviation industry is holding the last set of regional discussions this week aimed at

60 SECONDS

finalising a deal to cap its emissions from 2020. Airlines will either have to improve engine efficiency and convert to biofuels, or offset emissions by investing in reforestation projects.

The need is urgent, as industry expansion plans will see emissions rise three- or four-fold by 2040, says Annie Petsonk of the Environmental Defense Fund.

Limits on shipping emissions will also be discussed at a meeting of the International Maritime Organization, a London-based UN agency, later this month. Without such limits, it says, emissions would rise 250 per cent by 2050.

Sights set on red dwarfs

Space three-peat

MARK THIESSEN/GETTY

LET the little guys shine. The AND that’s the hat trick. On SETI (search for extraterrestrial 2 April, private space firm Blue intelligence) Institute is setting Origin launched its uncrewed its sights on the Lilliputians of the New Shepard rocket and capsule galaxy – red dwarf stars – in the into space and returned it safely hope that someone is home. to Earth – the third such success Over the next two years, the for this vehicle. The feat is a step institute will turn the 42 antenna towards making spaceflight less Allen Telescope Array towards costly with reusable rockets.

20,000 red dwarf stars to listen Until recently Blue Origin, for alien radio signals. owned by Amazon boss Jeff Bezos, “Red dwarfs were never considered kept it works mostly under wraps, very interesting for SETI in the past,” but with successful launches says Seth Shostak of the SETI under its belt the company is Institute. That’s because our sun starting to open up. It revealed isn’t one, plus they tend to be more the previous two New Shepard active than sun-like stars, shooting launches only after the fact, but out flares that could fry planets. on 1 April, Bezos tweeted that his But they make up 75 per cent of firm was preparing for take-off. the stars in the Milky Way. Based on “Working to fly again tomorrow.

Same vehicle. Third time.”

The firm has issued a video of New Shepard blasting off from a private launch site in Texas and reaching an altitude of 103 kilometres, scraping into space as it is usually defined.

Shortly after, the empty crew capsule separated from the booster and returned to the ground, safely slowed by parachutes. Meanwhile, the rocket hurtled back to Earth, only restarting its engine 3300 feet above ground. Balanced on its thrusters, it made a perfect –Looking for neighbours– touchdown.

population statistics of planets we’ve found in the past few years, the nearest red dwarf with a rocky, life-friendly planet could be as close as 6.5 light years away. These stars also live billions of years longer than sun-like stars, on average. That gives potential inhabitants a long time to grow up – and perhaps grow smart.

“With these developments in astronomy, it seems like red dwarfs are a good candidate,” Shostak says.

“They haven’t been given their 15 minutes of fame.”

The new survey will pick targets from a list of about 70,000 red dwarfs compiled by Andrew West at Boston University, and will listen to the stars in radio frequency bands between 1 and 10 gigahertz.

Farewell to Hitomi?

Japan’s troubled X-ray telescope may be no more. Launched in February, the Hitomi probe failed to communicate consistently with Earth when it started science operations on 26 March. Radar observations in early April suggest that Hitomi has now broken up into at least 10 pieces, and the craft has also ceased its intermittent beeps.

World Heritage threat Flora and fauna at 114 World Heritage Sites are threatened by industry, according to the WWF. Sites such as the Grand Canyon and the giant panda sanctuaries of Sichuan, China, are at risk from activities such as oil and gas exploration and dams, the NGO says.

Climate pacesetters On 29 March, Papua New Guinea became the first nation to submit a plan to combat climate change under the terms of the UN’s Paris agreement. The leaders of China and the US, which together account for 38 per cent of carbon emissions, jointly promised last week to sign the Paris deal on 22 April.

Superhot super-Earth A rocky world 40 light years from Earth has just had its temperature taken, and it is scorching. Exoplanet 55 Cancri e, a super-Earth roughly twice the size of our own planet, orbits its star in just 18 hours. A heat map of the planet reveals its day side is at over 2700 °C, while its night side reaches a relatively tepid 1100 °C (Nature, doi.org/bd2c).

Hand in self-storage Surgeons in Brazil are hopeful of saving the hand of a man who almost lost it in an industrial accident. They have tucked what remains of Carlos Mariotti’s hand into a cavity in his abdomen for two months. This should protect the hand from infection and supply it with blood, nutrients and growth factors that will help heal lost skin.

9 April 2016 | NewScientist | 7

This week

Gene therapy approved “WE NEARLY lost him twice,” says Kelly Gillion of her son Zeus, who was diagnosed with the potentially fatal condition ADASCID in the first weeks of his life.

Until now the only commercial treatment for the condition has been a bone marrow transplant, and many die before a donor is found. But last week, a gene therapy to treat it was rubberstamped for approval by a committee of the European Medicines Agency, potentially giving all patients in Europe access to a treatment that enables them to build lifelong immune systems with the help of transplanted genes.

The outcome has been hailed as a triumph for gene therapy after decades of high-profile setbacks.

“It’s an amazing moment and an absolute landmark for gene

therapy,” says Susan Walsh, director of PID UK, a charity representing parents and children with inherited immunodeficiency diseases. “The great thing is that an advance in one area improves prospects for other conditions,” she says.

Children with severe combined immunodeficiency (SCID) don’t have a working immune system and even routine infections can be fatal. The need to keep babies with SCID isolated has led it to be dubbed “bubble baby” disease.

In ADA-SCID, children have defective copies of the gene that makes adenosine deaminase (ADA), an enzyme indispensable to the immune system. Without it, toxic debris builds up in white blood cells and kills them before they can mature.

Zeus was lucky enough to

Getting out of the bubble “We couldn’t believe it when we were told he had pretty much no immune system,” says Kelly Gillion of son Zeus.

At 10 weeks he was diagnosed with a rare disease called ADA-SCID, caused by a deficiency of the adenosine deaminase (ADA) enzyme.

He was given synthetically produced ADA every week, which kept him alive while doctors searched for a bone marrow donor. “Our lives were turned upside down,” says Gillion. “No one could come round and see us if they had colds or coughs,” she says. “Basically, our family was in lockdown for a whole year.”

donor was found in Germany, placing Zeus among the lucky 60 or 70 per cent of patients who can be helped this way.

It’s not a pleasant treatment though. First the original bone marrow cells have to be wiped out using chemotherapy before they are replaced. “That was awful,” says Gillion. “It takes so long for the immune system to grow, he was still in isolation till he was 3.”

Now, Zeus is 6, at school and healthy, but Gillion says she knows of others who are not so lucky. Gillion is delighted that gene therapy will soon

Then, through the Anthony Nolan charity, a matching bone marrow

become available. “It’s great for the future of ADA-SCID,” she says.

8 | NewScientist | 9 April 2016

KLAUS GULDBRANDSEN/SCIENCE PHOTO LIBRARY

A treatment for kids lacking immune systems gets the go-ahead. Andy Coghlan reports

find a bone marrow donor gene therapy development at (see “Getting out of the bubble”, GSK. “The first patient is now below), but many children die 13 years post-treatment, and the as babies waiting for one. median over all the patients is An alternative treatment called seven years survival so far.”

Strimvelis should now become Although this is the first time available. It has been developed by this technique has won approval, teams at the San Raffaele Telethon for more than 20 years, children Institute for Gene Therapy in with ADA-SCID have been treated Milan, Italy, and pharmaceutical with a similar procedure on giant GlaxoSmithKline (GSK) and a trial basis at Great Ormond permanently alters DNA within Street Hospital in London and the a patient’s cells.

Necker Hospital in Paris. Cases of The procedure involves leukaemia in 2002 in four of the extracting the bone marrow stem treated French children led to cells that regenerate the immune suspension of that trial until 2005. system and infecting them with The virus used in Strimvelis is a harmless virus that uploads a correct copy of the gene for ADA. “I’m hesitant to call it a cure. But we have no The altered cells are injected back reason to suspect that into the patient where, unlike it won’t be indefinite” their native counterparts, they are able to generate a healthy immune system. the same as the one that gave To win approval, GSK rise to the leukaemia but GSK is submitted data on 22 patients, monitoring for complications. a mix of boys and girls treated The first and only other gene in Italy at an average age of therapy approval was Glybera 18 months. Full details are being in 2012, a gene product injected withheld for journal publication, into the muscles of people with but the company says that they lipoprotein lipase deficiency. were a success. “Of the patients in It makes the enzyme they lack – the trial, we’ve seen 100 per cent which breaks down fatty waste. survival,” says Sven Kili, head of The ADA-SCID treatment is the

In this section n The brains of the people who can never forget, page 10 n Is the war on drugs starting to fizzle out?, page 16 n Teaching robots to see like us, page 20

Planet Nine might be the sun’s stolen exoplanet

R. Hurt (IPAC)/Caltech

his colleagues think the chance that Planet Nine was an exoplanet ranges from 0.1 to 2 per cent.

“Although these probabilities seem low, you have to compare them to other [scenarios], and not OUR solar system might harbour “It would be pretty wild – to absolutely,” says Mustill. “Because an alien interloper. The proposed pick up an alien planet and bring ultimately any very specific Planet Nine lurking at the edge of it along for the ride,” says Greg outcome is very unlikely.” The the solar system could have been Laughlin at the Lick Observatory probability that the existing stolen from a passing star. in California. evidence for Planet Nine is all due In January, Konstantin Batygin To check just how wild, Mustill to random chance is just 0.007 and Michael Brown, both at the and his colleagues ran simulations per cent at present. So the fact that California Institute of Technology, of encounters between the solar the odds of it being an exoplanet announced evidence for an system and any passing planetary are 15 to 300 times higher than unseen planet around 10 times systems. They found that if that that actually bodes well for the Earth’s mass at the fringes of the exoplanet scenario (arxiv.org/ solar system. Other astronomers “The sun would have had abs/1603.07247). close encounters with immediately came forward with A fugitive on the run is just other stars, potentially suggestions for how so-called one way to explain Planet Nine, letting them swap planets” however. Batygin and Brown Planet Nine might have migrated from the inner solar system initially thought it was likely to towards its outer edges. a system happened to have a be the core of a gas giant ejected –Looking for a long-term solution– But one team now suggests wide-orbit planet, the likelihood from the inner solar system. “My just the opposite: that it was it would be captured by the sun pet theory is it happened early first that alters the DNA in stem captured from a nearby star. is about 50 per cent. and there was a lot of gas around cells taken out of the body and The idea isn’t all that far-fetched.

Those are pretty good odds, but in the solar nebula, and that gas in the future cells they produce.

The sun was born in a stellar they dropped when the team took sort of slowed it down and kept it “The gene we insert is assimilated cluster with roughly 1000 or into account whether the passing from being completely removed,” completely into the genome,” Kili maybe even 10,000 stars, says planetary system would have a Brown says. says. This should mean the effect Alexander Mustill from the Lund wide-orbit planet in the first This theory is relatively is long-lasting, even permanent.

Observatory in Sweden. In such a place. Also, it wasn’t enough to straightforward, says Scott Kenyon “We’re aiming for lifelong dense cluster, the sun would have just capture a planet: their of the Harvard-Smithsonian outcomes, so I’m hesitant to had quite a few close encounters simulations only worked if they Center for Astrophysics in call it a cure,” says Kili. “But the with other stars, potentially captured one that was exactly like Cambridge, Massachusetts. The stem cells we’ve altered go on letting them swap planets.

Planet Nine. Overall, Mustill and array of Jupiter-like exoplanets to replicate so we have no reason orbiting dangerously close to their to suspect that it won’t be host stars suggests that massive indefinite,” he says. planets regularly migrate inward.

Doctors at the Milan institute “Whenever you scatter something have also used the technique inward, to conserve energy, you’re to treat 20 children with a fatal, likely to scatter something else nerve-destroying inherited outward,” Kenyon says. disease called metachromatic And there’s one final option: the leukodystrophy. In future, the planet could have formed where team hopes to try it on an we find it now. Although some inherited condition called beta have speculated that there thalassaemia and even more wouldn’t be enough material in common conditions such as the outer solar system, Kenyon rheumatoid arthritis. found that there could be enough “We’ve seen the huge impact icy pebbles to form something as gene therapy can have on small as Planet Nine in a couple of children’s lives,” says Bobby hundred million years (arxiv.org/ Gaspar of Great Ormond Street. abs/1603.08008).

“Approval of a licensed gene “I think it’s premature to say therapy medicine for SCID is what’s most likely,” says Kenyon. a very positive step and shows A definitive answer will likely that gene therapy can become hinge on actually finding the –Kidnapped from another star?– unseen planet. Shannon Hall n a standardised medicine.” n 9 April 2016 | NewScientist | 9

This week

Roots of indelible memories traced “WHEN I recall my past, it’s like watching a home movie. I feel exactly how I felt. I’ll even feel the weather – if it was hot and sticky I’ll remember how tight my clothes were and what I was wearing.

All of my senses are triggered.”

This is how Bob Petrella, from Los Angeles, describes his gift.

Petrella is one of only 50 or so people who can remember every day of their lives as if it were yesterday.

Two studies by one team have picked away at what underlies this extraordinary ability. The results could eventually help treat anxiety and depression, and help us all to remember our past a little better.

Such exceptional power of recall is known as highly superior autobiographical memory, a term coined by neurobiologist James McGaugh at the University of California, Irvine. He and his colleagues have now performed a barrage of tests on 20 people with HSAM to see what cognitive processes might be critical to their memory. The tests probed areas like verbal fluency, pattern memorisation and the ability to

Ritual sacrifice’s link to unequal societies ARE modern societies built on bloody foundations? In traditional Austronesian cultures ritual human sacrifice was key to the emergence of inherited class systems, concludes a controversial new study. In this scenario, societies’ elite carried out these killings to control, terrorise and impress the lower ranks.

Joseph Watts and Russell Gray 10 | NewScientist | 9 April 2016

remember people’s faces and jobs.

Surprisingly, the results suggest that no particular ability underpins HSAM. People with HSAM scored only slightly better, and in only a few tests, than a control group of similar age (Memory, DOI: doi.org/bdxq).

In a second study, the team asked 30 people with HSAM to recall events that happened every day of the preceding week, as well as during a week that was 1 month, 1 year and 10 years earlier. The

at the University of Auckland, New Zealand, and colleagues browsed ethnographic data for evidence of

structure shifted to an inherited class system, and decreased the rate at which hierarchical societies

example, the study doesn’t exclude the possibility there were other causes of social hierarchical structure,

past ritual killings in 93 traditional Austronesian cultures.

They also noted the social structure of each culture today.

Was it egalitarian? Did it have an aspirational hierarchical structure, where individuals have some hope of raising their social status? Or an inherited class system where social status is decided at birth?

They found that ritual sacrifice increased the rate at which societies with an aspirational hierarchical

moved to egalitarian ones (Nature, doi.org/bdx9).

“Sacrifice does seem to have been performed in societies all around the world,” says Joseph Henrich at the University of British Columbia in Vancouver. But he and others disagree with Watts and Gray’s conclusions. For

says Michael Winkelman, now retired from Arizona State University.

Peter Turchin at the University of Connecticut thinks the new analysis misses a broader point, because the Austronesian cultures are all relatively small, lacking the complexities of larger societies around the world.

“Human sacrifice is actually a maladaptive cultural trait,” he says.

As societies grow and become more complex they dispense with human sacrifice, says Turchin. Colin Barras n

Sharon Vos-Arnold/Getty

Helen Thomson

quality and quantity of their memories were compared with those of a control group.

A month later, they took part in a surprise assessment of the same dates, allowing researchers to check the consistency of their memories (Frontiers in Psychology, doi.org/bdxp).

The team found that people with and without HSAM had comparable recall of events from the preceding week. But those with HSAM had a far superior memory of the more distant past.

The results suggest that people with HSAM are no better at acquiring memories – in other words, they aren’t superior learners – but are simply better at retaining memories.

McGaugh believes that their powers of memory may be rooted in a habitual rehearsal of their past. People with HSAM often show obsessive behaviours, similar to what is seen in obsessive-compulsive disorder (OCD). Petrella, for example, has to clean his car keys if they touch the ground.

The team don’t believe that people with HSAM actively try to memorise the past. Instead, they may accidently strengthen their memories by habitually recalling and reflecting upon their own lives. It could be a unique form of OCD, says McGaugh.

“The OCD idea fits,” says Tracy Alloway at the University of North Florida, Jacksonville. She says that the neural pathways we use in recall are like garden paths: if we don’t keep them organised, they become overgrown and blocked. “If you’re habitually recalling memories then you’re keeping those pathways clear, so you’re more likely to be able to retrieve that information faster at a later date.”

Poor recall is thought to be implicated in anxiety and depression, so understanding how to improve memory may eventually lead to therapies for such conditions. But for now, McGaugh says, his only quest is “to understand what’s happening in this marvellous machinery that –Total recall has an obsessive side– we call the brain”. n

“ Societies’ elite carried out these ritual killings to control, terrorise and impress the lower ranks”

This week FIELD NOTES New Zealand

Genetic matchmaking for parrots

AS I reach up into the manuka tree, the whiskered face of a giant parrot stares back at me before turning away from my grasp.

Fortunately, my colleague Daryl Eason manages to grab its large foot and slip a bag over its head, barely wincing when its huge bill clamps down on his finger.

We’re not here on Whenua Hou Island, off the southern tip of New Zealand, to harm the kakapo – we’re here to save the species, one bird at a time. The world’s largest parrot, the kakapo is flightless and has been under siege from nonnative mammalian predators, leaving it close to extinction.

Today, there are 123 adult birds sheltered on islands that lack these invaders, and we are using every available gadget and piece

Island refuge Whenua Hou Island is the main site of kakapo recovery in New Zealand

Auckland

NEW ZEALAND Wellington

Christchurch

Whenua Hou Island Stewart Island

12 | NewScientist | 9 April 2016

of scientific know-how to breed these birds back from the brink.

The bird in the bag is Gulliver, and we push our way through vegetation to inspect and weigh him, and check his transmitter harness. Every adult kakapo wears one of these tracking devices.

Monitored by plane, satellites and rangers on the ground, the data it transmits tells us when each bird is mating and nesting, and even who they have mated with.

In the breeding season, males develop an inflatable boom sac for calling to females, and Gulliver’s is huge, indicating he’s in the perfect condition to mate. Artificial female that has already mated, to insemination expert Sushil Sood boost their chances of successfully massages a few drops of semen hatching chicks. from his cloaca, and checks its Doing this also means we can condition under a microscope. ensure the genetic health of the Meanwhile, team manager species. In the 1990s, there were Deidre Vercoe collects his blood. just 51 birds, but we hope to avoid This will tell us how healthy he inbreeding by using genetic data is, including his vitamin D levels. to make sure that chicks have the We recently showed that kakapo, best possible combination of which are nocturnal so don’t often parents. Gulliver is genetically come into contact with sunlight, distinct from many of today’s have very low vitamin D levels. kakapo, so would be an ideal They feed their chicks the vitamin father, but at 18 years old, he is D-rich berries of the rimu tree, but still to father a single chick. the tree only bears fruit every two “ Our efforts probably or three years, and the birds can make the kakapo’s sex only breed in those years.

To help the birds along, we have life the most closely monitored of any species” been experimenting with food supplement pellets. Analysis of Gulliver’s blood will tell us if this We trek through forest for an is working. The DNA in his blood hour to find Kuihi, a female who will also be sequenced. Earlier would be a good genetic match for this year, we embarked upon an Gulliver. She is high up in a rimu ambitious project to sequence the tree, so we wait until nightfall, genome of every living kakapo – when she is likely to climb down. the first time anyone has tried to As the forest grows dark, the sequence a whole species. deep mating calls of male kakapo A whoop of delight from Sood boom around us. Once Kuihi’s tells us Gulliver’s semen quality transmitter tells us that she has is good. Every year, we attempt to reached the forest floor, we run artificially inseminate every adult after her by torchlight, finally Andrew Digby / New Zealand Department of Conservation

Andrew Digby

–Looking for love–

catching her at one of our supplementary feeding stations.

Courtship between a male and a female can last for over an hour, but it takes just a few minutes to inseminate Kuihi.

This nocturnal liaison doesn’t mark the end of our work. Around 40 of us have been working round the clock since the breeding season began in October, and until May we will be camping near every nest. Cameras and transmitters will tell us when a mother leaves her chicks, allowing us to discreetly weigh them, and alert us if the nest is in danger.

It’s exhausting work but it’s paying off. This year we are on course to beat our 2009 record of 33 chicks. There has been a huge crop of rimu berries and we currently have 37 chicks, plus one fertile egg left to hatch.

Our intensive efforts probably make the kakapo’s sex life the most closely monitored of any species. But we would do just about anything to ensure the future of the world’s weirdest parrot. n Andrew Digby is a scientist at the New Zealand Department of Conservation

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in Brief Insomnia linked to loss of brain circuits

How climate change affects bird winners and losers THEY may be separated by an ocean, but birds in the US and Europe are responding to climate change in a

birds are faring in relation to changes in the climate.

The degree to which advantaged birds are outperforming more disadvantaged species in the US and Europe has been similar (Science, doi.org/bdvj). “Climate seems to be having a consistent effect,” says Willis.

But there are differences. In Europe, disadvantaged

surprisingly similar way: winners are outperforming losers to a comparable degree.

In Europe, the brambling (top left) is losing out, while the chiffchaff (bottom left) is performing better. One of the biggest US winners is the orchard oriole (bottom right), while the Canada warbler (top right) is doing badly.

Stephen Willis of Durham University, UK, and his team

species have declined, while relatively advantaged species have remained more or less static. In the US, disadvantaged species have maintained stable population sizes, while those of advantaged species have grown.

“The two regions differ profoundly in their geomorphology and land-use history, and we would expect bird populations to have different opportunities

have used yearly bird number and location data from between 1980 and 2010 to see how some 525 species of

under climate change,” says Frank La Sorte at Cornell University in Ithaca, New York.

Martian dust devils gather their shadows FROM dust to more dust. On Mars, a dust devil’s own shadow can help the sandstorm grow.

On Earth, a light breeze is enough to lift dust grains into the air. But in Mars’s thin atmosphere, you need storm-speed winds, says Gerhard Wurm at the University of Duisburg-Essen in Germany – and these are rare on the Red Planet. Something must give the dust grains a helping hand.

14 | NewScientist | 9 April 2016

To find out what, Wurm emptied a capsule full of Mars-like sand grains down a drop tower.

This put the sand grains in free fall, eliminating the effects of Earth’s gravity.

Then he shone a laser on the dust grains as they fell. The light made the grains bounce around, but when it was turned off, they bounced even more readily, by a factor of 10, he says.

This suggests that the cooling caused by a dust devil’s own shadow could increase the amount of dust in the devil, possibly by causing movement of gases in the Martian soil, Wurm says (Icarus, doi.org/bdvm).

“This gas motion builds up a pressure below the surface, and if this is strong enough, the upper layer kind of explodes,” he says.

The explosion lifts sand grains into the air, where they join the dust devil.

CAN’T sleep? If you’re one of the 5 per cent of the population who has severe insomnia then you might have your brain’s white matter to blame.

Radiologist Shumei Li at Guangdong No. 2 Provincial People’s Hospital in Guangzhou, China, and her team scanned the brains of 30 healthy sleepers and 23 severe insomniacs using diffusion tensor imaging MRI, a technique that lights up the white matter circuitry.

They found that in the brains of those with insomnia, the regions in the right hemisphere connected with learning, memory, smell and emotion were less well connected compared with those of the sleepers. They attribute this breakdown to the loss of the myelin sheaths that normally surround part of the neurons in the white matter and help transmit signals (Radiology, DOI: 10.1148/radiol.2016152038).

Mosquitoes to get chemical weapons CALL them hommes fatales.

Equipping male mosquitoes with a chemical payload makes them lethal to other mossies.

The release of sterile males has already been shown to reduce populations. If the insects are also coated with pesticide, they transfer it to females and so to larvae. That makes them “10 to 100 times more effective”, says Jérémy Bouyer of CIRAD, in France. His team hopes to use the method to tackle the mosquitoes carrying Zika, dengue and malaria.

The approach works in the lab, Bouyer said at a tropical disease conference in London. If field trials are successful, it could be rapidly rolled out in specialist facilities like those being built in Brazil to combat Zika.

For new stories every day, visit newscientist.com/news

OCEANS on Saturn’s biggest moon might be bubbly like soda. The finding may account for at least one transient feature seen on Titan.

Besides Earth, Titan is the only place in the solar system with bodies of liquid on its surface. They are hydrocarbons at a frigid -180 °C and hold dissolved nitrogen gas.

Michael Malaska of NASA’s Jet Propulsion Laboratory in Pasadena, California, and his colleagues have found that this gas can bubble out of the ocean. In the lab, his team mixed nitrogen with ethane and methane at temperatures like those on Titan. They observed that the amount of dissolved nitrogen decreased as the liquid warmed.

On Titan, this would mean that a small amount of extra sunlight could unlock some of the gas, potentially making for some very big bubbles.

Malaska presented the work at the Lunar and Planetary Science Conference in The Woodlands, Texas, last month.

Such bubbles could explain a feature in Titan’s Ligeia Mare sea

NASA/JPL/University of Arizona/University of Idaho

nicknamed the “magic island”, which has repeatedly appeared and disappeared in radar images over the past few years. They also mean a proposed robot submarine for Titan would generate bubbles like dunking an Alka-Seltzer in water, a scenario that could have important implications for its design.

Rogue protein blocks new memories in Alzheimer’s THE mystery is starting to untangle. Twisted fibres of a protein called tau were long known to collect in the brain cells of people with Alzheimer’s, but their exact role in the disease was unclear.

Now a study in mice has shown how tau interferes with the strengthening of connections between neurons – the key mechanism for forming memories.

Li Gan and her colleagues at the Gladstone Institute of Neurological Disease in San

Francisco found that the brains of those with Alzheimer’s have high levels of tau with a particular modification, called acetylated tau. Using a mouse model of Alzheimer’s, they found that this protein accumulates at synapses, the connections between neurons (Neuron, doi.org/bdxk).

When we form memories, extra receptors for neurotransmitters are inserted into neural membranes at synapses, and this heightens their response. But acetylated tau depletes another protein called KIBRA, which is

essential for this mechanism.

“We’re excited because we think we now have a handle on the link between tau and memory,” says Gan. “We’re also cautious because we know this may not be the only link.”

Restoring levels of KIBRA reversed the effects of acetylated tau on neurons, at least in the lab. This offers a strategy for therapies, Gan says. “If we provide neurons with more of this protein, we can repair the lost synaptic strengthening that we usually observe.”

Jonas Bendiksen / Magnum Photos

Titan’s seas are full of fizz

Caribou mothers’ catch-22 dilemma WOLVES or bears? Such is the dilemma facing woodland caribou mothers, and they seem to be making the wrong choice.

Populations of this subspecies in the boreal forests of northern Canada have declined sharply in recent decades. Logging and oil extraction may be to blame, altering the caribou’s habitat and shifting the ecological balance.

Wolves were once the main danger to young caribou, but black bears are now thriving – and seem to have become the calves’ greatest threat.

Mathieu Leblond at Laval University in Quebec City, Canada, and his colleagues used GPS collars to track the movements of 26 adult female caribou for up to four years. They also tracked all 44 of the calves these females had over this period, as well as 12 black bears and nine wolves.

They found that wolves and bears tend to live in different areas, and that the calves of mothers that were best at avoiding the wolf habitats were less likely to survive (Journal of Applied Ecology, doi.org/bdvp).

“By being very good at avoiding wolves, they fall victim to the black bears,” says Leblond.

Clouds reveal where species live IT’S blue-sky thinking – sort of.

Patterns in the clouds can be used to decipher ecosystems on Earth more accurately than methods currently

of ecology,” says Wilson.

Wilson’s team has used the data to guess where two species with well-known distributions live: a

used for conservation.

Looking at 15 years of photos from NASA satellites, Adam Wilson of the University at Buffalo in New York and his team have built a database of daily cloud cover for nearly every square kilometre of Earth.

Because clouds affect the light intensity, rainfall and temperature below them, their patterns correlate with the biomes they float above.

“Sunlight drives almost every aspect

South American songbird and a South African shrub. Their cloud model predicted the distribution of these species better than conventional methods, honing in on a range 43 per cent smaller for the bird, and 18 per cent smaller for the shrub (PLoS Biology, doi.org/bdxs).

The tool could provide a cheaper and easier way to gather habitat data about hard-to-reach locations, and help decide which areas to protect.

9 April 2016 | NewScientist | 15

Analysis drug reform

Ending the war on drugs Nations are taking alternative paths in drug legislation, finds Clare Wilson

El Universal/REX/Shutterstock

JUST say no. That’s supposed to be our reaction to recreational drugs.

The trouble is, lots of people say yes please. As a result, the world’s governments have been waging a war on drugs for more than a century. Since 1961, the battle has been orchestrated via international treaties targeting all parts of the supply chain, from the producers to the smugglers, the sellers to the buyers.

Yet this supposedly united front has developed some conspicuous cracks. Now those countries backing a different approach have called a UN meeting later this month to make the case for change.

The question is whether the UN is ready to soften its stance or whether it will plough on despite mountains of evidence suggesting its zero-tolerance approach has failed. As the reformers collate this to present at the meeting, New Scientist looks at how the

16 | NewScientist | 9 April 2016

approaches taken by different wreaked by drug gangs, especially countries stack up (see “Drugs in countries where drugs are around the world”, right), and grown and trafficked. In Mexico, asks what can happen next. for instance, the number of deaths Some nations are already taking from the “narco wars” has started change into their own hands. reducing male life expectancy.

Portugal allows personal use of On the face of it, the UN any drug – including cocaine and meeting looks set to be a damp heroin – and several South and squib, with the three existing UN Central American countries are Drug Conventions unlikely to be moving in the same direction. superseded by a more liberal text.

As for cannabis, the number of “ Countries are going to get places where its open sale has more confident in their been decriminalised in some right to do what they think form grows ever larger. is best for their citizens” Most of these changes stem from the idea that while drugtaking has some health risks, a For while the US has softened zero-tolerance approach means its hawkish stance on drugs, other that those who become addicted countries have taken its place, cannot easily access treatment. particularly Russia and China.

And the majority who use drugs In many other countries, such without getting hooked are as the UK, politicians have staked criminalised, harming their life their careers on stamping out chances and putting pressure on drug use. Large sections of the justice systems. public wouldn’t stomach change.

Another catalyst is the damage Yet some think the open revolt

that’s set to happen at the meeting will be a turning point. “Countries are going to get more confident in their right to do what they think is best for their citizens,” says Amanda Feilding of the Beckley Foundation, a pro-reform NGO based in Oxford, UK. So what are the options for the reformers? In the short term they can express dissenting statements from the meeting’s official report.

Longer-term, they can try to negotiate exemptions, like Bolivia did when it left the conventions and returned only in 2013 when it got an amendment allowing its people to chew coca leaves.

Another option is for countries to negotiate breakaway treaties.

Even if countries choose to deviate from the conventions without official permission, it is unlikely there will be consequences. Realistically all the UN can do is issue disapproving reports; sanctions tend to be reserved for rogue nuclear states.

A key player could be Canada, whose new prime minister made a pre-election promise to legalise recreational cannabis. If a country with Canada’s financial clout goes down this route, possibly by following Bolivia’s example, then this would galvanise other nations, says Feilding. If Canada did manage it, it would be the first Western country to get around the conventions as medical legalisation and decriminalisation are technically within their wiggle room. (The US hasn’t officially flouted the rules as states that have legalised recreational cannabis operate under their own laws rather than federal law).

“This meeting is not going to be the end of the war on drugs,” says Steve Rolles of Transform, a proreform charity in the UK. “But it –Cannabis burns in Mexico– could be the beginning of the end.”

For daily news stories, visit newscientist.com/news

Drugs around the world

middle of a massive experiment,” says Stevens. “Each of the different models are going to have their benefits and disadvantages.”

ZERO TOLERANCE Sweden

and Crime, “the achievements of Sweden are proof that each government is responsible for the size of the drug problem in its country”.

But critics of the report say Sweden’s drug use is low simply because the culture has long been relatively abstemious, with similarly low use of alcohol and prescription drugs. There is also less social inequality – which can drive drug use – thanks to low unemployment and a generous welfare system.

The downside of zero tolerance is that harm-reduction measures like needle-exchanges are thin on the ground, and when people overdose their friends may not summon medical help for fear of being arrested. This means that despite low usage figures, the death rate from drugs is more than three times the European average, at about 70 per million people.

DECRIMINALISE USE Portugal

In Portugal you can take any illicit substance without fear of jail – ecstasy, cocaine, even heroin. Critics warned this policy, introduced in 2001, would encourage more people to take drugs. Instead, drug use is slightly down by most measures.

The biggest change has been the health gains for users. Deaths related to drug use have shrunk to less than one-quarter of what they were in 2001. New HIV infections among drug injectors have shrunk

HARD DRUGS ON PRESCRIPTION Switzerland

It might work for cannabis but it’s hard to imagine legalising access to harder –Kicking back at a Portuguese festival- drugs like heroin. Yet that is what has happened in Switzerland – and the evidence suggests it’s been a success.

The usual treatment for heroin

Ana Nance/Redux/Eyevine Nelson d’Aires/kameraphoto mark Henley/Panos

Some of the toughest drug laws in Europe are seen in Sweden. The country’s stated aim is to create a “drug-free” society, which translates into strict policing with zero tolerance of possession.

Levels of drug use are generally low compared with other parts of central Europe, and according to a report from the UN Office on Drugs

addicts is oral methadone, which dampens withdrawal symptoms without much of a high. But some people still can’t kick their habit. The idea of a heroin prescription is that it gives them time to sort their lives out, free from the worry of finding their next fix – and the money to pay for it.

The heroin is consumed at supervised clinics (see photo, left).

A study of 366 people accessing

–Growers in Colorado-

–A safe space in Switzerland- heroin prescriptions in Switzerland

to about one-twentieth.

Only the use of drugs has been decriminalised, not their sale, so criminals still profit. “But the policy

While many people smoke cannabis without problems, in a minority it does seem to trigger schizophrenia or dependence. Some fear that

was not brought in to reduce crime, it was to help people with drug dependence,” says Alex Stevens, who heads the International Society of the Study of Drug Policy, UK. “The evidence shows they have met their goals.”

Stevens says the health gains have

legalisation will mean more users and therefore more such health problems.

“It’s like oil or alcohol – if the price goes down and it’s more available, consumption will go up,” says Keith Humphreys, a psychiatrist at Stanford University in California.

not arisen from decriminalisation alone, but also from the services that were put in place when the law was introduced, like the provision of free needles for injectors, and methadone for those wanting to quit heroin.

Some countries are wary of letting market forces reign supreme. Spain, for instance, allows cooperative-like growers’ clubs, which don’t advertise or sell to minors. Uruguay plans to make it available through statelicensed pharmacies.

In Colorado, however, cannabis is now advertised in shop windows, free papers and phone apps. “That’s capitalism in action,” says Humphreys.

“But I think it’s a mistake to create another tobacco industry.”

California, which looks set to legalise cannabis in a referendum this year, is likely to take a more cautious approach, with health warnings and limits on advertising. “We are in the

FREE MARKET US states

The possession of small amounts of cannabis has been decriminalised in countries such as the Netherlands for many years, but now some places are going further and legalising its production and sale.

found that after six years, about half had managed to switch to methadone or quit using altogether. The rest were still taking heroin, but at least they no longer needed to steal or deal to fund their habit, says Ambros Uchtenhagen of the University of Zurich, who worked on the study. Other studies show the scheme slashes crime rates.

Prescribing heroin has been experimented with in other countries, such as the UK and the Netherlands, but it often faces public opposition, and the UK has recently cut back funding. But the Swiss backed the scheme in a 2008 referendum.

“They have seen it reduces the visible problems of heroin use, like people injecting in parks,” says Uchtenhagen.

Heroin use has been on the wane in Europe for some years but has recently risen in the US, Canada and Australia, probably triggered by wider use of prescription opiate painkillers.

In the US, things are so bad that the recent rise in drug overdose deaths has been described as looking like “a new infectious disease”. Despite this, in North America even methadone prescription is still controversial. n 9 April 2016 | NewScientist | 17

Comment

Reaping what we sow Staple foods are in nutritional decline as a result of loading the atmosphere with carbon dioxide, warns Irakli Loladze WE ARE undoubtedly pumping ever more carbon dioxide into the air. But did you know that this also silently adds unwanted carbs to bread, cereals and salad and cuts vital protein and mineral content?

This nutritional blow is now worrying the world’s most powerful nation. For the first time it forms a key finding in an official report on the health impacts of climate change in the US, drawn up by the Global Change Research Program (USGCRP) and unveiled by the White House this week.

Why would more CO2 mean poorer food? Photosynthetic organisms, such as plants, are the carbohydrate factories of the world. They convert CO2 and water into gigatonnes of starch and sugars every year. And every year since the industrial age began, we have steadily fed them more CO2.

Plants respond by building more carbohydrates but less

protein into tissues. This means a higher ratio of carbs to protein in plants, including key crops such as wheat, rice and potato. This is a double whammy: protein deficiency afflicts the developing world, while excess carbohydrate consumption is a worry in the obesity-riven developed world.

This is not the only nutritional impact. To capture CO, plants open pores in their leaves. These stomata let in CO2 but allow water out: plants compensate by sucking moisture from the soil.

Transpiration, as this process is called, is a major hydrological force. It moves minerals essential for life closer to the roots, nourishing plants and ultimately us. But plants respond to high CO2 by partially closing stomata and losing less water. This reduces the flow of nutrients to roots and into plants. Less minerals but more carbs creates a higher carbs-to-

Profiling genocide Painstaking DNA work helped bring Radovan Karadzic to book, says Thomas Parsons RADOVAN KARADZIC, the former Bosnian Serb leader, is beginning a 40-year jail sentence for crimes against humanity, genocide and war crimes during the 1992 -1995 Bosnian war. It marks the end of a trial that began in 2010 at the International Criminal Tribunal for the Former Yugoslavia.

Prominent among Karadzic’s 18 | NewScientist | 9 April 2016

the International Commission on Missing Persons (ICMP).

Profiling techniques were advancing to the extent that they could be used to account for tens of thousands of victims. The ICMP invited families of the missing to give blood samples, which were recorded and compared with DNA from human remains buried in clandestine graves.

This restarted an identification process that had reached its limit using traditional means and saw

offences was his role in the Srebrenica genocide, in which 8000 Muslim men and boys were executed in four days in July 1995.

Identifying them was a crucial part of ensuring justice was done.

Forensic work connected with this “ More than 70 per cent of the 40,000 people missing and the wider war became the largest DNA identification project at the end of the conflict the world had seen, carried out by have been accounted for”

an exponential rise in the number identified. It produced scientific data that could withstand the rigours of the courtroom.

Today, more than 70 per cent of the 40,000 people missing at the end of the conflict have been accounted for, including 7000 of the 8000 at Srebrenica.

DNA provided the prosecution with incontrovertible evidence that thousands of men and boys were murdered there. Moreover, the pattern of DNA linkages within and between primary and secondary graves provided evidence of systematic activities associated with the crimes and later attempts to conceal bodies.

For more opinion articles, visit newscientist.com/opinion

Irakli Loladze is an associate professor at Bryan College of Health Sciences in Lincoln, Nebraska. He co-authored a chapter of the USGCRP assessment

It also allowed thousands of families to recover the remains of loved ones and many of them got to secure their right to justice.

While identifying victims this way rarely by itself decides guilt or innocence, it does establish an objective factual framework that stands as a powerful antidote to tendentious narratives.

Those prosecuting war crimes now have at their disposal rigorous scientific methods that can establish a factual bedrock upon which to pursue justice. n Thomas Parsons is ICMP’s director of forensic sciences and provided evidence in Karadzic’s trial

INSIGHT Transgender health

Andrea Morales/NYT/Redux /eyevine

minerals ratio in crops and food.

In an elevated CO2 world, every serving of bread, pasta, fruits and vegetables delivers more starch and sugar but less calcium, magnesium, potassium, zinc, protein and other vital nutrients.

Over a lifetime, this change can contribute to weight gain.

Hidden hunger – the result of diets rich in calories but poor in vital nutrients – was mainly a developing world problem. But in 2002, New Scientist predicted that “elevated CO2 levels threaten to bring the... problem to Europe and North America”. Scepticism made it difficult to secure funding for testing this prediction and slowed progress by a decade.

However, the conclusion is now unequivocal: rising CO2 depletes protein and minerals in most food that underpins human nutrition across the world.

Sceptics like to claim that rising CO2 is a boon because it boosts crop yields. But as US Department of Agriculture scientist Lewis Ziska put it “elevated CO2 could be junk food” for some plant species.

There really is no such thing as a free lunch with climate change. n

–A plea for understanding –

Doctors must get up to speed on trans issues Jessica Hamzelou

patients’ health first. So what’s standing in their way?

Barrett says in his experience some doctors will say they don’t know enough about how to prescribe the relevant treatments (BMJ, doi.org/ bdvq). This isn’t just an excuse. For example, in the US in 2013, just 33 per cent of emergency medicine graduate programmes incorporated topics on LGBT health in their curricula. Those that did gave an average of 45 minutes to the subject. Trans people often point out that they have to

DOCTORS are failing their transgender patients. In the UK, an estimated 1 in 5 general practitioners are refusing trans people treatments such as hormone therapy, said James Barrett of the British Association of Gender Identity Specialists last week. “Some are remarkably frank, and say: ‘I’m not doing this as it is against my deeply held religious principles’.”

The problem isn’t confined to the UK. Surveys carried out in the US describe harassment, physical assault “Transgender people and denial of equal treatment in often say that they have doctor’s offices or hospitals. to teach doctors about What’s more, we know that trans trans care” people have a far higher rate of suicide – a 2010 study in the US found that 41 per cent had attempted it; the teach their doctor about trans care. national average is 1.6 per cent. But This lack of education can lead we also know that social support, doctors to refer trans patients to access to hormones or surgery, and mental health clinics, instead of reducing transphobia lower the gender identity clinics. As a first port of likelihood of a suicide attempt. call, this is wrong – while many people Doctors are bound to have the same will need counselling, feeling that your range of prejudices, personal beliefs gender does not match the one and religious views as the rest of us, assigned to you at birth does not mean but they have chosen a profession you have a mental disorder. that requires them to put their Part of the problem is how it is

defined by the medical community.

The World Health Organization’s International Classification of Diseases (ICD) still categorises “gender identity disorders” within the “mental and behavioural disorders” bracket. It also refers to “transsexualism”, which it defines as the desire to live and be accepted as a member of the opposite sex – when in fact many people choose not to identify as either male or female.

“The definition has so many problems I don’t know where to start,” says Timo Nieder, who runs a gender identity clinic at the University Medical Center Hamburg in Germany. Nieder is part of a group pushing to change the category’s name to gender incongruence, and remove it entirely from the ICD’s section on mental health disorders, changes that are scheduled to happen next year.

There are other signs that things are moving in the right direction. In March, the UK’s General Medical Council published advice urging doctors to support their trans patients.

There are also whispers of plans for the National Health Service to provide fertility-sparing treatments, such as egg or sperm freezing, for all those who start hormone treatment – as they do for cancer patients.

In the meantime, the front-line medical community needs to address the way it is failing to support a group of potentially vulnerable people, and recognise its duty of care. n 9 April 2016 | NewScientist | 19

Artur debat/Getty

Technology University in California are also trying to get computers to understand what’s happening in first-person video. But instead of learning from annotated footage, Augur was brought up on a very different data set: 1.8 billion words of fiction taken from Wattpad, an online writing community.

Events to chew over Fiction is a great resource for making predictions about human behaviour, says Ethan Fast, who leads the Augur project. “Fiction describes the breadth of human life.” Stories also tend to have a narrative structure that provides a logical sequence of events for a computer to chew over. “This thing happens, then this thing happens, then this,” says Fast.

–No, computer, it’s not a whirlpool– When Augur identifies an object in a scene, it mines what it has read to guess what a person might do with it. If it spots a plate, for example, it infers that someone is probably planning to eat, cook or wash up. If you wake up and look at your alarm clock, Teaching computers to understand the world as we see it will help Augur should guess that you are them understand us. Aviva Rutkin takes a closer look about to get out of bed.

One drawback of relying on “WHAT am I doing now? How fiction is that it has given Augur system that tries to predict interact with it easily? You are about now? And now?” University what objects someone might be a dramatic bent. If a phone rings, more likely to pick up a coffee students have been popping it thinks you are about to start interested in. Volunteers had to mug if its handle is pointed GoPro video cameras on their swearing and will throw the annotate videos of their day-totowards you, for example. heads and filming a first-person phone against a wall. Tweaking day lives frame-by-frame, to show Similarly, someone wanting to view of their daily lives, then the system using more mundane where their attention was focused use a computer will approach asking a computer to interpret it. scenarios will help teach Augur in each scene. They then fed the it keyboard-first.

Vain though it may sound, the that not everyone lives inside a footage into a computer and The team tested EgoNet on exercise has a point. Researchers soap opera. asked EgoNet over and over again footage that included people want artificial intelligences to The Stanford team will present to tell them what they were doing. cooking, kids playing, and a dog understand us better – and That data helped train it to make running in a park. It still has some Augur at the CHI conference in teaching them to see the world San Jose, California, next month. predictions, picking out things way to go before it can rival a through our eyes is a good place They will also show off its first that a person was about to touch “ One drawback of training to start. application, a Google Glass app or look at more closely. an AI on a diet of fiction is “It allows us to indirectly tap that plays a soundtrack for your EgoNet examines the world that it thinks everyone into human minds,” says Gedas life, choosing songs it deems through two lenses, backed by lives inside a soap opera” Bertasius at the University of appropriate for whatever it separate neural networks. One Pennsylvania in Philadelphia. perceives the wearer to be doing. looks for objects likely to stand “It allows us to reason much The team thinks future versions out to someone – because of being human, but Bertasius hopes a more accurately about human could help in other ways, such as brightly coloured, say, or being version of the system might be behaviour – the connection screening calls when it recognises centrally placed in the scene. The useful in healthcare, perhaps between what we see and how other estimates how each object helping doctors diagnose unusual that you’re busy, or reminding the we’re going to act.” wearer of their shopping budget might relate to that person. Is it behaviour patterns in children.

Bertasius and his colleagues are within reach? Is it oriented in a when it catches them eyeing the In a separate project called building EgoNet, a neural network way that allows the person to checkout counter. n Augur, researchers at Stanford

Do you see what I see?

20 | NewScientist | 9 April 2016

ONE PER CENT

For more technology stories, visit newscientist.com/technology

TINKERING with life just got easier.

A tool that lets you design DNA circuits using a simple language makes programming living cells as straightforward as writing code for computers. This will make it possible to create smart bacteria to help produce food or clean up oil spills, for example.

The tool is based on an existing language called Verilog, used to design

electronic circuit in shorthand – without worrying about the underlying hardware – and convert it into a detailed design automatically.

Voigt’s team realised they could do the same with DNA circuits.

Their system, called Cello, takes a Verilog design and converts it into a DNA wiring diagram. This is fed to a DNA synthesiser that generates a strand of DNA encoding the specified

electronic circuits. “We take the same approach as for a computer chip,” says Chris Voigt of the Massachusetts Institute of Technology. “Every step in the process is the same – it’s just that instead of mapping the circuit to silicon, it’s mapped to DNA.” Synthetic biology involves treating cells as machines that can be engineered. By altering a microbe’s

function. The DNA can then be

engineered cells as factories for therapeutic applications, such as bacteria engineered to be consumed like yogurt to produce healthpromoting substances in the gut.”

Voigt is working with bacteria that live on plant roots, giving them genes that scavenge nitrogen from the atmosphere and make it into fertiliser (PNAS, doi.org/bdtr). He hopes others will use Cello to build their own bacteria, and has made the tool freely available online. Oil companies could

DNA, it can be made to perform a specific task, such as producing a drug or changing colour when it detects a virus. Off-the-shelf genetic parts that can be swapped in and out make this easier, but it is still a painstaking

they were tried. One was the largest biological circuit ever built, with seven logic gates and strands of DNA 12,000 units long (Science, doi.org/bdvg).

“Cello will allow synthetic biologists to concentrate more on what they

more reliable, more opportunities for new applications will open up in different industries,” she says.

The work is yet another sign that synthetic biology is entering the mainstream, says Drew Endy at

process.

That’s where Verilog comes in.

Verilog is a symbolic language that lets you specify the function of an

want their microbes to do, and less on how to get them to do it,” says Matthew Bennett at Rice University in Houston, Texas.

Stanford University. “Programmers of biology will become more common than programmers of computers,” he says. Andy Coghlan n

“ Biologists can concentrate more on what they want microbes to do and less on how to get them to do it”

Would you take instruction from a robot? This is not hypothetical for employees of ad agency McCann Japan. Called AI-CD Beta, the artificial intelligence will guide the agency’s ad creation using data from analysed TV shows. It’s clearly a bit of a PR stunt, but the fact that it has been picked up shows the world is taking AI workers seriously.

“Government attacks on the encryption of online communication threaten human rights around the world.”

Brian van der Brug / Los Angeles Times via Getty

inserted into living cells. The team designed and tested 60 circuits – 45 of them worked perfectly the first time

develop smart bacteria that clean up oil spills. “You could load a sensor that responds to oil by activating an enzyme that degrades it,” Voigt says.

Christina Agapakis of Ginkgo BioWorks thinks the main beneficiaries will be businesses that do not necessarily have expertise in biology. “As the process to engineer organisms gets easier, cheaper and

Japanese bot does ads

Amnesty International comments on Apple's battle with the FBI over encryption

House, reconfigure What if you lived in one room? This is the vision of the Cube Project at the University of Hertfordshire, which launched the latest version of its microhome at the Edinburgh International Science Festival.

Designed for one person or a couple, the microhome aims to be energy neutral thanks to heat pumps, LED lighting, solar panels and triple glazing. The 18m2 floor is bordered by moving walls that can reconfigure between kitchen, lounge, bathroom and bedroom.

–Get microbes to do the work instead– 9 April 2016 | NewScientist | 21

McCann Worldgroup

Life hacker: now you can code cells like computers

With programming cells easier than ever, Voigt is convinced many new applications are just around the corner. “We’re on the cusp of seeing

Bots infiltrate insect groups to learn their ways FLICK on a light and cockroaches will swiftly disperse – only to regroup in the walls. A robot spy among them could help us understand how they coordinate and maybe even trick them into venturing into the light.

Bee bots have already been used to study waggle dances in honeybee hives. Now researchers are sending in robots to study the behaviour of other social animals, including fruit flies,

ORLANDO SIERRA/AFP/Getty Images

Technology Three of his wife’s friends came down with dengue at the same time. They all lived in different parts of Kuala Lumpur, but had recently met in a park.

It seemed likely that the park was the point of infection. Barnes, who runs his own software

“Once you find the source of the mosquitoes, you don’t need to blindly spray everywhere any more”

consultancy company, realised that if his apps could track where large numbers of people had birds and fish, and even influence been before getting infected, then their behaviour. overlay their location histories, But getting the robots to blend the major mosquito hotspots in can be tricky. In previous work, would emerge from the data.

José Halloy at Paris Diderot University People living nearby could then in France and his colleagues take extra precautions, and they –On target– or local authorities could focus on programmed their robot cockroaches largely by hand. This is difficult – and killing mosquitoes there rather cannot easily be adapted for other than spraying indiscriminately. types of animal. So Halloy’s team “Once you find the source, you developed a way to generate don’t need to blindly fog any behaviour automatically, combining more,” Barnes says. models of cockroach activity for both The idea is that people who Our smartphones hold information that would individuals and groups, then used have just come down with dengue evolving algorithms to optimise the would download the app and help tackle dengue. Michael Le Page reports bots’ movements. anonymously share their location The team tested the approach in a data for the past 15 days. The NO ONE wants a mosquito bite. simulation in which a mixed group of tropical diseases in London last trouble is that while Google keeps a 45 cockroaches and five robots had to But you really don’t want to be week. “Can we have an API please? history of its customers’ locations, cooperate to make a collective choice bitten by a mozzie carrying Allow the user to give access to it doesn’t offer any way for thirdbetween two shelters. They found dengue. “My youngest is bitten the last 15 days of location data party apps to request access. that the mixed group acted like real constantly,” says Steven Barnes, upon infection. Anonymously.

Would Google ever consider cockroaches – grouping along walls who lives in Malaysian capital We’ll do the rest.” letting its users opt in to sharing in realistic ways, for example – and Kuala Lumpur, a megacity in the Diseases like dengue and their location histories? Google behaved in more lifelike ways overall. grip of an outbreak. “It would be Zika spread after a mosquito didn’t say when New Scientist Signe Brewster n really easy for her to get infected.” feeds on blood from someone asked, but it has previously said To fight back, Barnes has infected with the virus. After it is interested in helping the fight created an app called Fight a few days’ incubation, the against Zika.

Dengue that tells users if mosquito will then pass the Even if Google does play ball, anyone nearby has the disease. virus on to anyone it bites in success will depend on lots of If so, they know they should the remaining weeks of its life. infected people sharing their take extra precautions to avoid The mosquitoes that carry these data. But it would be in people’s being bitten. He built the app for viruses don’t usually fly more than interests to do so, not just to personal use, but Fight Dengue a few hundred yards. So if one protect family and friends, but has gathered 400 users since he of your neighbours gets dengue, because coming down with one made it freely available. He is your risk of catching the disease strain of dengue doesn’t stop you also working on apps for malaria is higher than if the nearest case getting the other four strains, so and Zika, and wants to make them is a kilometre or two away. A few catching it is still something you all better with data to which only months ago, something happened need to avoid. The terrible pain Google has access. that gave Barnes an idea for these later infections can cause “Dear Google,” Barnes’s slides tracking the disease and the give the disease its nickname, –Roach or robot?– read at a conference on neglected insects that spread it. “breakbone fever”. n

Frank Greenaway/Getty

Spot that mozzie

22 | NewScientist | 9 April 2016

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Aperture

24 | NewScientist | 9 00April Month 2016 2016

How to fix a shadow HE WAS a man of some accomplishments, but drawing eluded him. So while on honeymoon in Italy in 1833, William Henry Fox Talbot adopted the camera lucida, a tracing device, to help him sketch scenes. “The idea occurred to me,” he later wrote, “how charming it would be if it were possible to cause these natural images to imprint themselves durably, and remain fixed upon the paper.”

Although not the first to develop a photographic process (the Frenchman Louis Daguerre is usually handed those laurels), Talbot remains the godfather of the modern “art of fixing a shadow”. His first photographs highlighted the precision and fine grain of the new medium. Later work is wittier and more domestic, as by then Talbot had developed photography as an art for everyone. His company in Reading, UK, massproduced paper prints from his calotype negatives. It also made prints from others’ negatives, copied artwork and documents, and took portraits.

In 1934, Talbot’s niece Matilda passed on 6500 items of his to London’s Science Museum.

From 14 April a new exhibition, Dawn of the Photograph, presents the best of these, including fragile early experiments in the art. Simon Ings

Clockwise from top left: Two images of William Henry Fox Talbot and Nicolaas Henneman at the Reading establishment, 1846; The Latticed Window (with the Camera Obscura), August 1835 ; The Ladder, April 1844; The English Vine (Bryonia dioica), probably 1839; Melrose Abbey, 1844

Photographer William Henry Fox Talbot © National Media Museum, Bradford/ Science & Society Picture Library 00 Month 9 April 2016 | NewScientist | 25

OPINION INTERVIEW

Supercharged coral vs climate change By giving evolution a helping hand, Ruth Gates is creating corals tough enough to survive in increasingly hostile oceans

What does your coral project consist of?

It’s an ambitious project to breed coral able to survive the enormously challenging conditions brought on by climate change.

Our research facility is on Coconut Island in Hawaii, a small island off the coast of Oahu, where the opening shots of the TV show Gilligan’s Island were filmed. It’s incredible.

I get into a tiny boat each morning to go to work. The island is surrounded by coral reefs: I am literally sitting in the middle of our experiment.

What are the goals of this work?

We are exploring why some corals survive conditions that kill others. We will then 26 | NewScientist | 9 April 2016

For more opinion articles, visit newscientist.com/opinion

Photographed for New Scientist by Elyse Butler Mallams

Profile Ruth Gates is a marine biologist and director of the University of Hawaii’s Hawaii Institute of Marine Biology at Coconut Island, where she leads the Gates Coral Lab

the rates of decline in reefs are outpacing their evolutionary capacity to adapt to ocean acidification and warming waters. But I’m trying to combat the doom and gloom surrounding the idea that virtually all corals will be dead by 2050. Such a scenario raises awareness about the need to mitigate the effects of climate change, but the message that all corals are going to die is not one that empowers and engages people. We should be doing everything we can to reduce our burning of fossil fuels, but in parallel we should be doing everything in our power to stop the decline of reefs.

their ability to respond to stress and imprint a memory they will retain and hopefully pass to their offspring via epigenetics. Thirdly, we will tweak the symbiosis a bit by introducing new high-performing algae that will feed the corals more efficiently, making them as healthy as possible to face the rigours of the future.

Fourthly, my collaborator Madeleine van Oppen at the Institute of Marine Science in Australia will be hybridising corals, taking closely related species and creating offspring that we hope will be more resilient than either of the two parent species.

What will you do with these “super corals”?

One threat to reefs is bleaching as a result of environmental stress. What happens?

You go from this teeming, brilliantly coloured, three-dimensional underwater city to a flat pavement covered with a scum of grey-green algae. It is very distressing! Coral polyps have these tiny plants, or microalgae, living inside their cells. The microscopic plants produce food and give it to the coral, so corals essentially have a food factory living within

“ We’ll take high-performing corals – super-athletes – and breed them together ” their tissues. It is a mutually beneficial relationship. The brownish colour of typical corals reflects high densities of these microalgae within the polyp. When a coral undergoes some kind of stress – such as exposure to warmer water – you see a paling and whitening as the coral expels its algae.

Is such bleaching terminal for a reef?

selectively cross-breed the healthiest specimens, a technique that is common in agriculture but has never been attempted in corals before. We’ll take high-performing individuals – super-athletes – and breed them together. By the end of our five-year mission, in 2020, we hope to have a significant stockpile of highly resilient coral strains and a plan in place to use them to restore completely denuded and partially damaged reefs in Hawaii and Australia.

What’s the outlook for coral in general?

As a biologist who has looked at reefs for 30 years, I’m realistic about what I see – and it’s not pretty. Few would argue with the fact that

If severely bleached, the animals usually die.

But if the stress is relieved before that stage, the microalgae in the corals will regrow and the coral will rebrown and survive. Hawaii had massive bleaching events in 2014 and 2015.

But what is remarkable is that here in Kaneohe Bay, 70 per cent of the corals that bleached last year recovered. It shows that there is a surprising level of resilience in the system.

That’s the fifth and final step. We will assist in the migration of corals by introducing our best performers from places where they are doing well to places where corals and reefs are weaker, so they can reproduce with the existing population, making it hardier.

Will you send Hawaiian super corals to Australia?

A coral reef in Hawaii has a very different species assembly from elsewhere in the Pacific, so we won’t be moving coral between Hawaii and Australia. The goal is to develop the capacity in both places to breed coral from the local stock for use in that location.

How soon will you be introducing super corals?

We are currently in the proof-of-concept phase, determining whether or not we can actually breed super corals. Within a year or two, we aim to move some of our corals from our first group of experiments at inland nurseries to shallow-water nurseries in the ocean. These will be intermediate areas, where they will be observed prior to reintroduction to the reefs from which they came.

What factors might cause your programme to falter?

If we already knew how to do it, it wouldn’t be cutting-edge science. But the issues that I anticipate relate to whether we can keep the corals alive in lab conditions for an extended period. For example, we are growing baby corals on tiles, and if we get an infection in one of the tanks, will we lose biology?

So does your project aim to harness this natural variability in resilience?

Is it difficult to grow coral in the lab?

Yes, and we are doing five things. First, we will selectively breed individuals of a given species on the reef that we know are doing well.

Secondly, we will condition corals to make them more resilient to stress. In other words, we will have coral organisms in tanks and give them experiences that we think will mobilise

It is not easy. Coral is difficult to culture, which is why it generally doesn’t do well in aquaria.

The advantage of our lab is that we are working adjacent to a coral reef and using unfiltered water pumped directly out of it. So we are taking the corals out of their native setting into as similar a one as we can possibly provide. > 9 April 2016 | NewScientist | 27

OPINION Will you need special permission to put these super corals on natural reefs?

Absolutely – we need to get permits from the Hawaiian government. The state has invested an enormous amount of money on an inland nursery that holds and grows endangered species of corals, so is very interested in our work, and we are discussing a partnership.

We also need permission from local residents.

It is important that we have this discussion with everybody to convince the public at large of the urgent need to act.

Is this type of work truly necessary, given recent research on coral’s surprising ability to bounce back?

Yes, because whatever resilience is there in the system is being overwhelmed by the rate of change in the environment. Will nature repair itself? In some cases, yes, but for every story of spontaneous recovery, there are 10 stories of reefs that have been wiped out.

Could releasing super corals have drawbacks for biodiversity?

Climate change has already wiped out 30 per cent of Hawaii’s corals – that’s a significant amount of diversity gone. The genetic narrowing that we are going to see with coral breeding should be considered against the backdrop of those kinds of ongoing losses.

Is there an ethical dimension to altering reefs?

In places in Hawaii, we have completely denuded settings where there is no reef or fish left. People who live in those places and depend on the reef for their livelihood are saying that they absolutely want us to carry out these interventions.

When a reef dies, islands lose a defence against storm waves and as a result can start to lose their land mass. And the people lose their main food source – with 70 per cent of the protein eaten in the Pacific coming from the reef – so they have to migrate, becoming refugees. The clear risk of doing nothing is a catastrophic ecological and social collapse.

This seems a very proactive type of science.

There’s no time to waste, so we won’t be sitting on our results, waiting to publish them years later. We’ll be setting up websites and releasing our data as they come in, so that others can learn from our successes and failures at almost the same time as we do.

It is a new collective form of science – a global collaboration with people as committed to the mission of saving reefs as we are.

28 | NewScientist | 9 April 2016

What sparked your passion for the oceans?

I call myself a child of Jacques Cousteau.

His television shows, with those spectacular underwater visuals, were my inspiration. I also had an amazing lecturer who was able to make coral reefs come alive for me – in a classroom in the north of England, of all places.

Can you imagine a world without reefs?

From top left: Reef coral (Pocillopora damicornis) in the lab; Gates and team take a close look; research boats on Coconut Island; coral (Montipora capitata) to be exposed to warmer, more acidic conditions

No, and no one should live with this outcome.

Reefs are crucial to the biodiversity of the seas, providing nurseries where countless fish and other species live and reproduce, many of which we eat. But they are fabulous ethereal underwater gardens scaled like a cathedral – vast structures that you can see from space, created by millions of tiny organisms.

Swimming among reefs, you have this incredible awareness of being in a world full of colour and teeming with life, created by something so much bigger than yourself. n Interview by Richard Schiffman

COVER STORY

On the road again From our origins in Africa we’ve conquered the world by migrating.

Can modern immigration really be a crisis, asks Debora MacKenzie 9 April 2016 | NewScientist | 29

opening page image: sam falconer Alex Majoli/Magnum Photos

H

UMANS migrate. It is a characteristic of our species. Yet now a migration crisis is headline news. More than a million desperate people fled to Europe in 2015, and nearly 4000 died trying. The influx is increasing and about to swell more as the weather improves. The United Nations says Europe faces “an imminent humanitarian crisis, largely of its own making”. And it is not alone.

The UN has also censured Australia for sending boatloads of refugees to squalid camps in other countries.

And US politicians talk of building a wall while tens of thousands of lone children flee violence in Latin America across the US-Mexican border.

In January, the World Economic Forum ranked large-scale refugee flows as its global risk of highest concern. When the US Council on Foreign Relations drew up its top 10 priorities for conflict prevention in 2016, it included political instability in the EU caused by the influx of migrants. Concerns about refugees and economic migrants are grist to the mill for those who want Britain to vote to leave the EU in June. And there’s no doubt that migration will increase as the world’s economy becomes more globalised, and as demographic and environmental pressures bite.

Should we be alarmed? What is the truth about migration? It is an emotive issue. But the scientific study of what happens when humans move is starting to supply some non-emotive answers. It’s showing that many widespread beliefs don’t hold up to scrutiny. “Concern about immigrants falls sharply when people are given even the most basic facts,” says Peter Sutherland, the UN Special Representative for migration. One analyst even says that removing all barriers to migration would be like finding trillion dollar bills on the sidewalk.

A species on the move 30 | NewScientist | 9 April 2016

200,000 years ago Homo sapiens appears in what is now East Africa

125,000 Humans leave Africa for western Asia, but settlements later replaced by Neanderthals

The millions fleeing Syria have shone a spotlight on refugees, but that tragedy is just a small part of a bigger picture. More than 240 million people worldwide are international migrants.

Refugees account for fewer than 10 per cent of the total and, in theory, they are the least contentious group, because many countries have signed international commitments to admit them. The rest are moving to work, or to join family members who have jobs.

When such people travel with refugees, they are often derided as “just” economic migrants. This is unfair, says Alex Betts, head of the Refugee Studies Centre at the University of Oxford. Whether or not they meet the official definition of a refugee, many are escaping dire conditions that pose a threat to their survival. Although globalisation of the world’s economy has lifted millions out of poverty, it has not been able to create enough jobs where there are people in need of work.

Aid funds are starting to address this problem – but for the most part people must go where there are jobs.

That’s why some see migration as a crisis. The 2008 financial crash spawned insecurity about jobs and concerns about economic migrants. Several populist parties took the opportunity to warn of a flood of freeloaders at the gates, increasing the issue’s political visibility and hardening the policies of some mainstream parties, including in the UK. The US government decided not to bail out firms that hired too many immigrants. Spain paid migrants to leave – even after they had stopped coming as jobs disappeared. And feelings of insecurity remain.

“The logic driving this is the idea that migrant workers present additional competition for scarce jobs,” says Ian Goldin at the University of Oxford.

Indeed, it is probably part of our evolved nature to think that more for you means less for me (see “The Origins

THE ORIGINS OF XENOPHOBIA All the evidence suggests that migrants boost economic growth.

So why don’t we just fly people who want to work to countries where there are jobs and welcome them with open arms? Prejudices rooted in humanity’s evolutionary past may be partly to blame.

“Perceptions of competition drive a lot of our thinking and are difficult to avoid,” says Victoria Esses at the University of Western Ontario in London, Canada.

Humans think of their support systems as a zero-sum game – so if one person gains, another must lose out. Such perceptions were accurate during our evolutionary history as hunter-gatherers when the appearance of others on our patch meant fewer mastodons or mushrooms for us. If they were close relatives they might share – or at least our common genes would benefit from their success.

But anyone displaying different

cultural markers was likely to be a competitor. A modern capitalist economy is not a zero-sum game – if you add more workers, it grows (see main story). Regardless of this, our evolutionary hang-ups make it difficult to accept the economic sense in welcoming immigrants.

That’s not all. We are instinctively wary of close contact with strangers because in our evolutionary past this helped us guard against infectious disease, says Mark Schaller at the University of British Columbia in Canada. Separate groups of people often have different histories of exposure and acquired immunity to pathogens.

A disease carried innocuously by one might devastate another, as happened to the Native Americans after Europeans arrived.

Steven Neuberg at Arizona State University in Tempe notes that groups also evolve different survival-enhancing practices.

of xenophobia”, above). But that’s not how modern economies work.

If economies really were zero-sum games in this way, wages would go down as labour supply increased and natives might well lose jobs to immigrants. But no modern economic system is that simple, says Jacques Poot at the University of Waikato, New Zealand. The knock-on of economic migration is that increased labour also brings an increase in profit, which business owners can invest in more production. They can also diversify, creating opportunities for a broader range of workers. In addition, migration means workers can be more efficiently matched to demand, and make the economy more resilient by doing jobs natives won’t or can’t do.

“Foreigners with different rules might interfere with the social coordination you need to do important tasks, or might get members of your group to follow their rules instead,” he says. “Chaos could emerge if your group makes decisions by consensus but theirs is authoritarian.”

Schaller and Neuberg believe that for both these reasons, human cultures evolved to be wary of close interaction with people who were different from their group.

This xenophobia persists, says Neuberg, who has found that people feel threatened by groups with different values of many kinds. Ethnic groups in modern cities often form enclaves rather than mixing randomly – which can foster strong local communities but also engenders wider mistrust.

To live in multicultural societies, we will need to learn to get past such evolved tendencies.

“More people expand the economy,” says Goldin, because people are moving from where they cannot work productively to where they can. In a survey of 15 European countries, the UN’s International Labour Organisation (ILO) found that for every 1 per cent increase in a country’s population caused by immigration, its GDP grew between 1.25 and 1.5 per cent. The World Bank estimates that if immigrants increased the workforces of wealthy countries by 3 per cent, that would boost world GDP by $356 billion by 2025. And removing all barriers to migration could have a massive effect.

A meta-analysis of several independent mathematical models suggests it would increase world GDP by between 50 and 150 per cent. “There appear to >

100,000

75,000

60,000

46,000

44,000

Humans head to east Asia, interbreeding with Neanderthals along the way

Humans reach West Africa

Humans leave Africa via the Middle East

Humans reach Australia

Humans reach Europe

9 April 2016 | NewScientist | 31

bettmann/Corbis

Millions migrated to the Americas in the 19th century, but far more stayed at home

THE RELUCTANT MIGRANT Humans have always migrated.

Our species started as African apes and now covers the planet. Tales of migration are central to our religions, our literature and our family histories. And migration is at the heart of modern life. I am a migrant. You may be too. Some 38 per cent of scientists working in the US and 33 per cent in the UK are foreign-born. Yet they may be exceptions to an ancient rule: in fact, few people migrate. And when we do, often it’s because we feel we have no other option.

Take our ancient ancestors who left Africa between 65,000 and 55,000 years ago. At the time, humans had evolved 35 different lineages of mitochondrial DNA, a collection of genes that changes very slowly. The migrants were carrying just two of these, which with other DNA data suggests that they could have numbered as few

16,000 years ago Humans reach the Americas

32 | NewScientist | 9 April 2016

as 1000. The vast majority of human diversity outside Africa stems from this single migration, suggesting this small band of pioneers may not have gone far, occupying the first lands they came to in the Middle East and discouraging followers. Their descendants would then have expanded into further territories when those hunting grounds got crowded. In this way, over tens of thousands of years, humans occupied the world, moving first to Asia and Australia, then to Europe, and finally colonising the Americas.

The biggest emigration the world has ever seen is much more recent. A mass movement of people from Europe to the New World occurred between 1850 and 1910. At its peak, over 2 million people a year were relocating.

Nevertheless, the vast majority chose to stay put. On average, only

5 per cent of the population of Britain – among the biggest sources of migrants – left each decade.

Today, just 3.3 per cent of the world’s people are migrants, little more than in 1990. Even within the European Union, where citizens are free to live wherever they choose, only 2.8 per cent, 14 million people, now reside outside their native country. “The idea that, without controls, everyone moves is contradicted by the evidence,” says Philippe Legrain at the London School of Economics. “Niger is next to Nigeria, Nigeria is six times richer and there are no border controls, years ago 200,000 but Niger is not depopulated.

Sweden is six times richer than Romania, EU permits free Homothe sapiens appears in what isbut now East Africa movement, Romania is not depopulated.” Even strong economic incentives are often not enough to tempt us to leave home.

be trillion-dollar bills on the sidewalk” if we lift restrictions on emigration, says Michael Clemens at the Center for Global Development, a think tank in Washington DC, who did the research.

But who gets those billions? Most of the extra wealth goes to migrants and to their home countries. In 2015, migrants sent home $440 billion, two and a half times the amount those countries received in foreign aid – promoting development and jobs at home. But what do natives of countries that attract migrants get out of it?

In the EU it has been difficult to tease out the effect of free movement of workers from other economic results of membership. However, a study of non-EU member Switzerland is illuminating. Different parts of Switzerland allowed free access to EU workers at different times, enabling Giovanni Peri of the University of California, Davis, to isolate the effects.

He found that while the workforce grew by 4 per cent, there was no change in wages and employment for natives overall. Wages increased a little for more educated Swiss people, who got jobs supervising newcomers, while some less educated Swiss people were displaced into different jobs.

Peri has also looked at the situation in the US. “Data show that immigrants expand the US economy’s productive capacity, stimulate investment and promote specialisation, which in the long run boosts productivity,” he says.

“There is no evidence that immigrants crowd out US-born workers in either the short or the long run.” Natives instead capitalise on language and 125,000 other skills by moving from manual jobs to better-paid positions. Peri calculates thatHumans immigration to the leave Africa for US western Asia, but the between 1990 and 2007 boosted settlements later average wage by $5100 – a quarter of replaced by Neanderthals the total wage rise during that period.

Further evidence comes from a meta-analysis Poot did in 2010, which

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collated all the research done up until bring in education paid for by their that point. It reveals that rises in a native countries, and many return to people in the EU are citizens country’s workforce attributable to their homeland before they need social of a country other than the foreign-born workers have only a small one where they live security. Based on recent numbers, effect on wages, which could be positive Britain should conservatively expect or negative. At worst, a 1 per cent rise 140,000 net immigrants a year for the workers in the EU are caused wages to fall by 0.2 per cent, next 50 years. The Office for Budget citizens of a country other mostly for earlier generations of Responsibility, the UK’s fiscal than the one where they live immigrants. The impact on the watchdog, calculates that if that availability of jobs for natives is number doubled, it would cut UK 20.7 million 13.6 million 6.5 8.5 “basically zero”, he says. Any tendency government debt by almost a third – are from are from other million million outside the EU EU countries for wages to fall with an increase in while stopping immigration would are from are from immigration can be counteracted by up the debt by almost 50 per cent. other EU outside enforcing a minimum wage.

Illegal migrants make a surprising countries the EU The UK Migration Advisory extra contribution, says Goldin. While Committee came to a similar many work “informally” without conclusion in 2012. “EU and non-EU declaring income for taxes, those SOURCE: EUROSTAT migrants who have been in the UK in formal work often have taxes for over five years are not associated automatically deducted from their pay Those who do end up in wealthier with the displacement of British-born cheques, but rarely claim benefits for countries are not the burden people workers,” it reported. Very recent fear of discovery. Social security paid sometimes assume. The Organisation migrants do have a small impact, but by employers on behalf of such for Economic Co-operation and mainly on previous migrants. What’s migrants, but never claimed by them, Development, which represents more, the ILO notes that low-skilled netted the US $20 billion between 1990 34 of the world’s wealthiest nations, migrants do “dirty, dangerous and and 1998, says Goldin. That, plus social calculates that its immigrants on difficult” jobs, which locals do not security contributions by young legal want – crop picking, care work, cleaning average pay as much in taxes as they migrants who will not need benefits for take in benefits. Recent research shows and the like. Meanwhile, highly skilled decades, is now keeping US social migrants plug chronic labour shortages that EU workers in the UK take less security afloat, he says. in sectors such as healthcare, education from the benefits system than native “One of the dominant, but and IT. Nearly a third of UK doctors and Brits do, mostly because they are empirically unjustified images is of younger on average. Moreover, they 13 per cent of nurses are foreign-born. masses of people flowing in… taking Another presumption made about away jobs, pushing up housing prices migrants is that they put a strain on and overloading social services,” writes benefit systems. This is also not borne Stephen Castles at the University of out by the evidence. “It is widely Sydney, Australia, and two colleagues assumed that economic migrants are in their book, The Age of Migration. mainly poor people out to live off the They argue that an increase in tax money of the relatively rich,” says migration is often the result rather human rights expert Ian Buruma. “Most than the cause of economic changes of them are not spongers. They want to Source: UN Population Fund that harm natives – such as neoliberal work.”

A lot go not to countries offering economic policies. “The44,000 overwhelming 75,000 46,000 100,000 60,000 generous benefits, but to where there majority of research finds small to no are jobs. Some 82 million people, 36 per effects of migration on employment cent ofhead the world’s current migrants, Humans reach and wages,” says Douglas Nelson of Humans leave Africa Humans to east Asia, Humans reach Humans reach West Africa via the Middle East interbreeding withone developing Australia have moved from Tulane University in New Europe Orleans.

Neanderthals along the way country to another, especially from “On purely economic grounds, Haiti to the Dominican Republic, Egypt immigration is good for everyone.” to Jordan, Indonesia to Malaysia and That may come as a welcome surprise Source: World Bank Burkina Faso to Ivory Coast. to many. But economics is not the >

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9 April 2016 | NewScientist | 35

AGE CONCERNS

yuri kozyrev/NOOR

As birth rates plummet in the developed “That is what people tend to see,” anxiety over the loss of cultural says Goldin. He says investment is world, migrants are keeping our economies homogeneity has been blamed for required to mitigate these problems. afloat. They account for half of the increase a backlash against immigrants.

“Governments need to manage the in the US workforce since 2005, and 70 Elsewhere, there has been a costs, which tend to be short-term and per cent in Europe. Even so, the number hardening of attitudes. Ellie Vasta local,” he says. That’s a challenge, but it of people of working age supporting each of Macquarie University in Sydney, can be done. Bryan Caplan of George retiree over 65 is falling. In 2000, this Australia, is trying to understand Mason University in Fairfax, Virginia, “dependency ratio” was 4:1 across the why Europe, which embraced points out that since the 1990s, 155 European Union. Today it is 3.5:1. And even multiculturalism in the 1970s, today million Chinese have moved from the with current levels of migration it is set to calls for cohesion and nationalism, countryside to cities for work. “This fall to 2 by 2050. demanding that immigrants conform shows it’s entirely possible to build new In 2000, the UN Department of and testing them for “Britishness” or homes for hundreds of millions of Economic and Social Affairs ran a detailed “Dutchness”. She blames an increasing migrants given a couple of decades.” simulation to see how many immigrants loss of cohesion in society due to China may be managing the biggest would be needed to support the “individualising” forces from mass mass migration in history, but there’s population over 65 in developed countries. media to the structure of work. As one problem it mostly doesn’t face.

They found that with no migration, people rely more on their own Perceived threats to national identity Europe’s population is set to fall 17 per resources, they have a longing for often top natives’ list of concerns about cent by 2050 – with a 30 per cent The presence125,000 of foreigners ago 200,000 yearscommunity. immigrants. It can even be an issue decrease in people of working age. To appears to disrupt this, creating a when such identities are relatively maintain overall numbers, the EU needs “desire to control differences”, she says. leave recent constructs. But countries with Homo sapiens appears in 850,000 immigrants per year – for Research by RobertHumans Putnam at Africa for what is now East Africa western Asia, but a clear ethnic identity and no recent comparison, the net migrant number from Harvard University suggests this move settlements later history of significant immigration face outside the EU in 2013 was 540,000. away from multiculturalism could be replaced by Neanderthals the biggest problem, says Nelson. “It’s However, to keep the working-age problematic. He finds that increased Refugees account tricky for Sweden, which went from population from falling, it needs nearly diversity lowers “social capital” such for fewer than essentially no immigrants to 16 per double that: 1.5 million a year. That would as trust, cooperation and altruism.

10 per cent of total However, this can be overcome in cent in half a generation,” he says. And mean recent migrants and their children migrant numbers Denmark is another nation where would account for 14 per cent of the UK societies that accommodate, rather population and over a third of Germany’s than erase, diversity by creating “a new, 11,000 16,000 years ago 8000 6000 4500 and Japan’s. Even then, the dependency broader sense of ‘we’”. In other words, ratio would be just over 2. The US fares success lies not in assimilation, but in better – current and expected migration adaptation on both sides. Canada has Mainland Europeans Humans reach Farmers from Middle East In Sumeria, first cities attract Yamnaya pastoralists kept its dependency ratio at 3. tried achieve this by basing follow retreating ice the Americas invade Europe and interbreed migrants andto spawn from its the steppe “Migration might be the most relevant national identity on immigration. into Britain with hunter-gatherers technological innovation invade Europe force to have an impact on the age Canadian prime minister Justin distribution in Europe to 2050,” says Trudeau told the World Economic demographer Pablo Lattes, an author of Forum in Davos, Switzerland, this the study. Germany, which has a shortfall year that “diversity is the engine of of 1.8 million skilled workers, is keenly investment. It generates creativity aware of this. Officials have been saying that enriches the world.” quietly at international meetings that this This view is shared by complex AD have 800accepted so many of 980 1220 systems analyst Scott Page 1200 1492 is why they at the Europe’s current wave of refugees. In University of Michigan, Ann Arbor.

2000, the government tried to bring in He argues that culturally diverse Vikings colonise Migrants from Mongols spread Columbus reaches the Caribbean, Vikings migrate to 20,000 foreign high-tech workers, but groups, from cities to research teams, Britain northern Mexico across Eurasia sparking a wave of migration from Iceland, Greenland this was met with strong oppositionand from consistently outperform less diverse establish Aztec empire Europe to the Americas Newfoundland the public. Germany may hope refugees groups due to “cognitive diversity” – will be harder for people to object to. exposure to disagreement and

alternative ways of thinking.

AD 1913

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Bolshevik revolution in Russia displaces more than a million people into western Europe

Second world war displaces 30 million people

18 million people move between India and Pakistan following partition

36 | NewScientist | 9 April 2016

Si Barber/eyevine

“Immigration provides a steady inflow of new ways of seeing and thinking – hence the great success of immigrants in business start-ups, science and the arts,” he says. But more diversity means more complexity, and that requires more energy to maintain – investment in language skills, for example. The fact that immigrants have settled more successfully in some places than others suggests that specific efforts are required to get this right. Achieving broad agreement on core goals and principles is one, says Page.

We had better learn how to manage diversity soon because it’s about to skyrocket in wealthy countries. As birth rates fall, there’s a growing realisation that workers100,000 from abroad will be 75,000 46,000 44,000 60,000 markets for poor countries. This would Migrants make managed by foreign ministries, not required to take up the slack (see “Age economies more labour ministries that understand the concerns”, left). In addition, the fertility worsen unemployment and political Humans reach Africa by doing Humans head to east Asia, Humans reach reach resilient and also massively Humans boost leave job market.

“What could be ofHumans real value of incomers can stay higher than that of instability – West Africa via the Middle East interbreeding with Australia Europe jobs that natives pressure. would be for governments, companies natives for several generations.

In 2011, migration Neanderthals along the way won’t or can’t One way to prepare for this would and trade unions to get together and for the first time since mass European be to take a more coordinated and look at where the labour shortages are, migration in the 19th century, more strategic approach to the global and how they could be filled, with non-white than white babies were workforce. As it is, it’s hard to track natives or migrants,” says Michelle born in the US, mainly to recent Asian migration amidst a mess of nonLeighton, head of migration at the ILO. and Hispanic immigrants and their standardised data and incompatible Amazingly, says Goldin, there is no children. By 2050, white Americans rules. Countries do not agree on who is global body to oversee the movement will be a minority, says Bill Frey of the 3000 1500 AD 370 450 632 a migrant. Even the EU has no common of people. Governments belong to Brookings Institution in Washington policy or information for matching the International Organisation for DC. That’s good news for the US, he people to jobs. Migrants are usually Migration but it is not an official UN adds, because it gives the country a Humans populate Eurasian Huns move west, Anglo-Saxons Western Eurasians Arabs spread across western agency so cannotAsia set common policy. younger workforce and outlook than Polynesia driving Germanic tribes into from Denmark move back into eastern and North Africa creating Instead, each country jealously guards its competitors in Africa Europe and Japan.

Rome, leading to its fall colonise Britain then southern Islamic caliphate its borders while competing for workers.

Even if we finesse multiculturalism, Goldin and others think there should there is a potential game changer be a UN agency managing migration in looming on the horizon. Massive the global interest, rather than leaving automation and use of robotics it to nations with differing interests – could make production less and power. This, combined with real dependent on human labour. empirical understanding of the This “fourth industrial revolution” 1851 1847of migration, might finally 1520 paying their 1820 1840 impacts may see governments allow humanity to capitalise on the citizens a guaranteed minimum wage huge positive potential of its ancient independent of work. There has been 50,000 Chinese people 1.5 million Irish Start of the age of mass Europeanof ships penchant for moving. n migrate to join the little discussion howstart this might 2.6 million Europeans living in people flee famine to the New World, a quarter of migration from Europe to transporting slaves from affectWest a mobile global workforce.

California gold rush Britain and America them indentured servants North America and Australia Africa to the New World Debora MacKenzie is a consultant for However, some warn that cheap, New Scientist based in Brussels. See automated production in wealthy Source: Migration Observatory, University of Oxford online version for links to research countries could destroy export

4%

of the UK population were foreign citizens in 1993

8.5%

of the UK population were foreign citizens in 2014

1975

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UN High Commissioner for Refugees counts 2.4 million refugees worldwide

UNHCR counts 12.1 million refugees worldwide

UNHCR counts 15.1 million refugees worldwide

9 April 2016 | NewScientist | 37

Picture Credit

38 | NewScientist | 00 Month 2016

The hole story

I

Jan Kornstaedt/Gallerystock

What happens to the stuff a black hole sucks in? To find out, we need to unleash the weirdest fluids ever created, says Anil Ananthaswamy

MAGINE lying in a giant bathtub when someone pulls the plug. Sliding towards a watery exit from this world, it gets worse.

The fluid gathers pace to supersonic speed and you realise no one can even hear you scream.

Your sounds are transported with you down the drain, lost to the bathtub for all time.

It is the stuff of surrealist nightmares – and a pretty fair description of what happens to an atom or a photon of light as it crosses a black hole’s event horizon. Black holes famously devour anything that comes too close: light, matter, information. In doing so, they cause some almighty headaches for our best theories of physical reality.

Or do they? Although we are pretty certain black holes exist, we’ve never observed one directly, let alone got up close and personal.

That’s where the bathtub analogy is now coming into serious play. Get fully to grips with it, and we could have a new way not just to fathom black holes, but also to crack some of cosmology’s other toughest nuts – from why the expansion of the universe is accelerating to how it all began.

There’s a catch, naturally. To make the analogy real, we can’t use any old water from the tap. It takes a fluid so extreme and bizarre that it was fabricated for the first time just 20 years ago, and only exists within a whisker of absolute zero, the lowest temperature there is. With that magic ingredient, you can begin to make a superfluid sonic black hole.

Black holes are the most mysterious of the many predictions made by general relativity, Einstein’s theory of gravity that he formulated just over a century ago. General relativity is a peerless guide to the workings of gravity, but puts gravity at odds with the other known forces of nature. Unlike them, gravity is not caused by the exchange of quantum particles; instead, massive bodies bend space and time around them, creating dents in the fabric of the universe that dictate how other bodies move.

The world according to general relativity contains some shady spectres – invisible dark matter to explain why galaxies whirl at the speeds they do, and dark energy to explain why the expansion of the universe is accelerating. The theory also fails completely when you wind the universe back to its first

instants and the big bang. Here, it predicts a seemingly nonsensical “singularity” of infinite temperature and density.

Still, black holes take the biscuit. We now think these impossibly dense scrunchings of mass exist across the cosmos – where massive stars have collapsed in on themselves, and at the heart of galaxies including our own.

For all their heft, however, black holes seem strangely tenuous, at least in theory.

In 1974, physicist Stephen Hawking used quantum rules to show that all black holes must eventually evaporate, apparently destroying any information they might have swallowed, a physical no-no.

According to quantum physics, spacetime is a roiling broth of particles and their antiparticles that pop up spontaneously in pairs, disappearing again almost instantaneously. But when such a pair pops up at the edge of a black hole’s event horizon – the point beyond which nothing can escape its gravity – sometimes one will have the energy to whizz away, while the other falls in. By the law of conservation of energy, this second particle must have negative energy, causing the black hole to slowly lose its oomph and evaporate.

The signal this is happening is a faint stream of escaping partner particles – Hawking radiation.

In theory at least, Hawking radiation has a temperature: the smaller the black hole, the warmer it is. For a black hole 30 times the mass of our sun, it is a titchy nanokelvin or so, impossible to measure in the chaotic surroundings of an astrophysical black hole. Hopes were high that the Large Hadron Collider at CERN near Geneva, Switzerland, might produce mini black holes with measurable Hawking radiation – but not a peep. “This is a pity, because if they had, I would have got a Nobel prize,” Hawking said in a BBC lecture this February.

Wind back to 1981, however, and physicist William Unruh of the University of British Columbia in Vancouver, Canada, was thinking of ways to study Hawking radiation. It led him to some strange parallels between the “metric” – a mathematical construction in general relativity that expresses the geometry of space-time – and equations used to describe superfluid flow. > 9 April 2016 | NewScientist | 39

“ It is an entirely different state of matter beyond solid, liquid and gas”

WHAT ARE BLACK HOLES MADE OF? For all we know, it could be snails and puppy-dog tails. There is no microscopic theory of a black hole’s innards, but Georgi Dvali of the Ludwig Maximilian University of Munich, Germany, thinks we might find clues in parallels between how black holes and Bose-Einstein condensates process information.

Black holes are careless stewards of information, apparently dribbling it away as they evaporate (see main story), but they are efficient stores of it. It would take about 10-5 electronvolts of energy to stuff one quantum bit of information into a cubic-centimetre box.

To stuff that qubit into a black hole of the same size – which would have the mass of Earth – would take 1066 times less energy, says Dvali.

Intriguingly, Dvali and his colleagues have shown that Bose-Einstein condensates seem to process information similarly to black holes.

“There is a one-to-one correspondence,” he says. “In particular, the system delivers very cheap qubits for storing information.”

Bose-Einstein condensates exist in a so-called quantum-critical state, transitioning from a normal state to one in which all the atoms act as a coherent quantum whole. Dvali speculates that the parallels indicate that black holes are quantum-critical states too – albeit not of atoms, but of quantum particles of gravity known as gravitons.

40 | NewScientist | 9 April 2016

Experimental verification of Unruh’s idea would have to wait.

Then, in 1995, came a Nobel-prizewinning development: the creation of the first BoseEinstein condensates (BECs). This is an entirely different state of matter beyond solid, liquid and gas, made up of collections of atoms cooled down to temperatures so low, sometimes a few nanokelvin above absolute zero, that the individual atoms lose their identity. They occupy the same quantum state, and behave and flow as one.

Sonic event horizon Creating this extreme, bizarre form of superfluid was an experimental tour de force, and came with an important detail as far as the black hole story was concerned: in a BEC, the speed of sound is just millimetres a second. Sonic black holes suddenly looked feasible.

Iacopo Carusotto, a theorist at the BEC Center in Trento, Italy, was initially a sceptic.

But returning from holiday in 2005, he found himself sitting next to a college friend on a train who turned out to be a gravitational physicist, and the two got talking shop. The friend introduced Carusotto to Roberto Balbinot, an expert on general relativity at the University of Bologna. These two started to build computer models of sonic black holes that took into account factors such as how the speed of sound varies according to how a fluid is moving, its temperature, the wavelength of the phonons and so on.

Carusotto still has the first image spewed out by the simulation in 2008 hanging on the wall in his office. “I jumped off my chair,” he says. It shows that as a Bose-Einstein condensate starts flowing at supersonic speeds, a sonic event horizon forms and phonons of Hawking radiation spontaneously appear. “To see it so precisely in agreement with theory was a great surprise, and a great success,” says Carusotto.

Jeff Steinhauer, an atomic physicist at the Technion-Israel Institute of Technology in Haifa, was the man who could make the analogy an experimental reality. He had developed some crucial tools: a way of measuring a condensate’s temperature to an accuracy of a nanokelvin, and complex systems of adjustable magnetic fields to stop condensates sagging and being disrupted under the effect of real gravity. By 2009, he was able to use lasers to accelerate a long, thin stretch of condensate to supersonic speed. The result was the first sonic black

NATIONAL INSTITUTE OF STANDARDS AND TECHNOLOGY/SPL

Unruh showed that the equations governing such flow at supersonic speed mimicked the metric of space-time around a black hole. This implied a superfluid could create a black hole that would trap “phonons” of sound, just as an astrophysical black hole traps photons of light. It’s the surrealist nightmare, with an added twist.

Just as with an astrophysical black hole, quantum fluctuations would make a sonic black hole emit Hawking radiation – but made of phonons, not photons.

Unruh realised this could be just the thing to test Hawking’s idea. Prove the radiation exists in one situation, and the mathematical mirror provides a pretty good indication that it does in the other.

He was rather ahead of the times. Although the first superfluid state was created in liquid helium in the late 1930s, for a sonic black hole the fluid had to be flowing faster than the speed of sound in that fluid – in superfluid helium, that’s hundreds of metres a second.

hole with an event horizon (Physical Review Letters, vol 105, p 240401).

Measuring individual phonons to verify the existence of Hawking radiation proved more tricky. In 2014, Steinhauer reached a halfway house by accelerating a thin condensate stream to supersonic speed and then allowing it to slow again. This created the equivalent of two event horizons – a black-hole horizon from which no sound could escape, and a “white-hole” horizon into which no sound could enter. In such a situation, Hawking phonons produced by the black hole bounce between the two horizons, producing more and more Hawking radiation in a similar way to how light is amplified in a laser.

And amplified radiation is certainly what Steinhauer saw. “It was very exciting to suddenly see this effect,” he says. “It was very gratifying to think that the physics Hawking predicted was creating it.” The question raised

by Carusotto and others since is how to tell for certain whether the initial phonon was created by spontaneous, random quantum fluctuation rather than some classical process.

Final confirmation could be coming soon: Steinhauer currently has a paper under peer review in which he reports seeing unadorned Hawking radiation from a single

PASCAL GOETGHELUCK/SPL

sonic horizon (arxiv.org/abs/1510.00621).

Steinhauer himself wouldn’t discuss this work further, but theorist Stefano Liberati of the International School for Advanced Studies in Trieste, Italy, is excited. “If this result is confirmed, it’s definitely a major breakthrough,” he says. “It would be the first experimental detection of Hawking radiation.”

Whether it’s enough for Hawking to get his Nobel prize remains to be seen, but Liberati

the energy of empty space and whose effect thinks this work is just the beginning. Not only would be to expand space ever faster, just as might sonic black holes illuminate further dark energy is thought to do. But calculating mysteries of the real thing (see “What are the value of this constant from observations black holes made of?”, left), but get superfluids gives a number 10120 times smaller than the flowing in different ways and you can create value you get from quantum field theory. other space-time geometries that equate to Again, Bose-Einstein condensates could other cosmological problems. One is the hold the answer. In a condensate, not all the exponential expansion of the universe in the atoms that you cool down end up in the period known as inflation, thought to have lowest-energy condensate state: you never occurred immediately after the big bang. get a perfect condensate. What’s more, these Current cosmological theories predict that during this phase, the quantum fluctuations of stragglers “backreact” with the condensate, space-time also got stretched, eventually giving an interaction that appears in the equations in a similar way to the cosmological constant. rise to the particles we see everywhere today.

We can’t test this idea directly, but Liberati and his colleagues have shown how a similar “ The superfluid analogy situation implemented using a condensate should give rise to phonons. “You should might provide clues to be able to reproduce the salient features dark energy” of cosmological particle creation,” he says.

One way of doing this involves using To Liberati, this is suggestive of the real lasers or magnetic fields to suddenly nature of dark energy, and space-time itself. compress a condensate, thus changing What if the fabric of the universe, and hence the speed of sound within it. This creates gravity, emerge from some as-yet-unknown an analogy to the change in light’s travel “atoms” of space-time, just as a superfluid time between two points in space as the state emerges from normal atoms when they universe expands. In 2012, Christoph are cooled? If some of these atoms are left Westbrook and his colleagues at the Charles over and do not form the basis of space-time, Fabry Laboratory at the University of Paristhen their backreaction with those that do Sud in France did just that and saw indirect could reduce the value of the cosmological effects of phonon creation – although constant to match what astronomers find. the experimental temperature of 200 In this view, the equations of general nanokelvin was still too high to rule out relativity might just be a high-level picture thermal fluctuations as the source. that emerges from a more fundamental Liberati suggests that a similar analogy description. In fluid dynamics, the set of could provide clues to another huge equations known as Euler’s equations cosmological conundrum, dark energy. The similarly describes the flow as a whole, but peculiar problem of dark energy is not so not the molecular interactions that underlie much that it exists. General relativity allows it. “It’s teaching you a very important lesson,” for a “cosmological constant” that represents says Liberati. “If gravity is emergent, the only way you can calculate the cosmological Bose-Einstein constant is by knowing the fundamental condensates system from which gravity emerges.” arise (above) The quest for a more fundamental picture when supercooled of gravity is central to the search for a “theory gases of atoms of everything” that will finally unite all the all enter the same forces of nature, gravity included. So far, quantum state convincing answers have been thin on the ground – in part because we have lacked any way to test ideas experimentally. In that sense, listening carefully to sounds swirling through superfluids could be the stuff of physicists’ dreams, rather than their nightmares. “It’s a success story,” says Liberati. “It’s a case in which theoretical physics finally made connection with experiments.” n Anil Ananthaswamy is a consultant for New Scientist 9 April 2016 | NewScientist | 41

predictive processing story. Brains have to reduce prediction errors if we are to perceive the world correctly – a must for survival.

They can, of course, do this by “finding the predictions that best accommodate the current sensory inputs”, explains Clark.

They can also do this by making our bodies move, forcing them to seek sensations so that hypotheses can be verified or rejected, refining internal models.

As Clark writes, neatly alluding to the book’s title: “We are not cognitive couch potatoes idly awaiting the next ‘input’, so much as proactive predictavores – nature’s own guessing machines forever trying to stay one step ahead by surfing the incoming waves of sensory stimulation”.

This is a book for which most of us will need to brace ourselves: it is more monograph than popular science, which means the going is tough. But grappling with technical language and concepts is repaid with fresh insights and intensely evocative moments.

For example, Clark sees the predictive brain as an “actionoriented engagement machine”, constantly configured and reconfigured by the body and the environment, which in turn are being shaped by a voracious brain as it seeks to make sense of the outside world. As he puts it: “This pattern repeats at more extended scales of space and time, as we structure (and repeatedly

“ We are not cognitive couch potatoes idly awaiting the next ‘input’, so much as proactive predictavores” restructure) the social and material worlds that slowly but surely structure us.”

Cognitive processes like attention also fit well into the story. Attention, in predictive processing, assigns high integrity to incoming data, so that any prediction errors are taken more seriously and internal models updated as needed. On the other

Christopher Anderson/Magnum Photos

For more books and arts coverage, visit newscientist.com/culturelab

hand, if you are doing something mostly without paying conscious attention, prediction errors don’t carry the same import, and internal models hold sway.

Crucially, the fact that a brain filled with such internal models can generate sensory data on its own, independent of actual sensations, allows us to imagine, to dream and to time-travel mentally. We owe our inner lives to “probabilistic generative models”, as obtuse as that sounds.

This inner life includes perception of our own body: according to the predictive-processing idea, even our sense of being embodied emerges from generative models that try to infer the causes of both external and internal sensations (such as signals from the gut).

But predictive processing , it turns out, comes with a dark side. Predictions can go awry, leading to delusions and

We may be closing in on the secret hallucinations, for example, in of how consciousness emerges people with schizophrenia. This also shows how perception and not overstating the case, cognition may not be as distinct peppering his book with caveats as we once believed: what we for balance: “If the predictive know and how we think can processing story is on track” is influence perception, which one favourite. in turn modulates thought There are dangers in being and knowledge.

Of course, predictive processing seduced by the allure of predictive processing. But proof, one way can’t explain how consciousness or the other, may come from emerges from the material brain.

But Clark is optimistic. “Might we, our efforts to create intelligent and conscious agents, and from inch-by-inch and phenomenonseeing how they do what we do. by-phenomenon, begin to solve It may be a tall order, but as the so-called ‘hard problem’ of Nobel laureate Gerald Edelman conscious experience?” he asks. and Giulio Tononi pointed out “It is far too early to say, but it in their book A Universe of feels like progress,” he answers.

Consciousness: “After all, it In Surfing Uncertainty, Clark has been done at least once by makes a formidable case for evolution.” They meant our predictive processing, one that brain, of course. n synthesises the work of many well-known researchers, such as Geoffrey Hinton and Karl Friston. Anil Ananathaswamy is a consultant for New Scientist But he is suitably cautious in 9 April 2016 | NewScientist | 43

culturelab

Peripheral concerns Sometimes, for our own sanity, we should just let our cities sprawl, says Pat Kane orthodoxy. He especially hates the way that it downgrades and patronises the suburbs. The problem goes beyond where to house the service workers. It’s really about how middle and working-class families are to retain their connection to the dynamism of urban life.

The Human City: Urbanism for the rest of us by Joel Kotkin, Agate $24.95 Practicing Utopia: An intellectual history of the new town movement

by Rosemary Wakeman, University of Chicago Press, $45

44 | NewScientist | 9 April 2016

“The vertical build is now part of the showbiz that cities must conduct if they aspire to world status”

michael wolf

NO MATTER what ambitious mayors and tech companies may tell you, cities have always been “smart” cities: evolving habitations with a huge appetite for powerful ideas.

From their earliest days, cities have not only concentrated power, whether religious, imperial or productive, but have self-consciously dramatised it too – in their towering buildings and straight streets, their marketplaces and monuments, their intellectual and political cultures. The bustle and grandeur of cities like Mecca, London, Paris and Jerusalem (or Beijing, Athens, Amsterdam and Rome) has persisted for over a millennium.

Today, national governments appear both distant from their citizens and ineffective in the face of global markets and other forces. So thinkers, policy-makers and activists are turning their attentions back to the city, that enduring polity within which the progress of the populace can be both imagined and realised, street by street, public arena by commercial district.

Do cities serve us best when they are dense and compacted, or dispersed and sprawling? How much of the “smartness” of a city comes from the technocratic brilliance of its planners and developers at the top, and how much from the emerging demands of denizens rubbing along together?

Joel Kotkin’s The Human City

is a long and lucid argument against what he regards as the current orthodoxy – that highdensity living in the core, rather than suburban sprawl, is the optimal design for the modern urbanopolis.

Dense thinking This orthodoxy is backed by what may seem conflicting interests.

Environmentalists love the dense city because it urges people out of their cars and on to public transport systems, packing and stacking people in residences designed for energy efficiency.

Activists also treasure the compacted city – a place whose streets and squares make civic and political pressure visible.

Equally, the dense city can support hubs for talent and

Hong Kong storeys: cities are more various than their buildings suggest

capital, providing specialised services to the world economy in what Kotkin calls glamour zones. This kind of activity requires offices, housing and leisure developments close to each other, and taken to a glittering level.

Look from the 72nd floor of The Shard in London – itself a glamour zone – and you see city constructions erupting competitively into the sky.

Compelled as a necessity by the island limits of Manhattan, the vertical build is now part of the architectural showbiz that cities must conduct if they aspire to world status.

From any angle, Kotkin isn’t impressed with the dense city

Kotkin says we should value suburbs since these are the places that generate the children who will one day walk the city’s boulevards, and dream of inhabiting its penthouses. For where is the space, time and even appetite for bringing up a family in the glass canyons of the smart and expensive centre?

Yes, urban cores are exciting, transient places – platforms for young professionals, students and the cosmocrat class to circulate excitedly on their way to the next talent-intensive gig. But Kotkin reckons cities are at their healthiest when they nurture the aspirations of their own citizens, and this means planning for dispersal as well as concentration.

The implicit approach of Kotkin is pragmatic. By contrast, Rosemary Wakeman’s Practicing Utopia is a compelling but mildly chilling record of dogmatism.

According to her book, a post-war generation of town planners believed that systems thinking and cybernetics were master disciplines, ones that could help design ideal living environments for any population.

Norbert Wiener, who pioneered cybernetics in the West, dubbed

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LETTERS editor’s pick

How I became a cancer drug fan From Steve Wilson I had the possibly unique experience of reading your article about drugs that allow the body’s immune system to tackle cancer (5 March, p 34) while a cannula fed one of these, nivolumab, into my body.

This was about 12 months after being told that I had perhaps a year to live – but there was a drug trial I could qualify for.

There were (from memory) three pages of possible side effects, the risk of which I had to agree to, from mild to death. I didn’t hesitate. I had looked up my condition – kidney cancer metastased to adrenal gland and lungs – and had found nothing to suggest that recovery was even possible.

When I first went to see my oncologist after the treatment started he didn’t mess about with any introductory remarks or dramatic voice, he just told me: “all your tumours have shrunk”. I won’t forget that day in a long time, and I seem to have a long time, since fewer than a third of my tumours remain.

When I was a teenager I would pore over Melody Maker and the New Musical Express looking for mention of any of the strange new “underground” bands I loved. Now I have the same odd satisfaction in seeing ipilimumab and nivolumab in print.

London, UK

To read more letters, visit newscientist.com/letters 52 | NewScientist | 9 April 2016

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Health data safety in Scotland From Harry Burns You report a recent Wellcome Trust study that identifies public concern about the use of anonymised patient data by the National Health Service in England (12 March, p 6).

NHS Scotland is completely separate from the NHS in England and is accountable to the Scottish Parliament. Scotland has long been a pioneer in the use of linked health service data for research, and we have been working on an approach that addresses the serious issues of safety, security and transparency of data.

Following extensive public consultation, we have developed an approach for data linkage that removes personal identifiers such as names and dates of birth from data used for health research. The Scottish Informatics and Linkage Collaboration, of which I am cochair, is leading innovation. Every aspect of its work is underpinned

by Guiding Principles for Data Linkage. We fully agree with the Wellcome Trust’s view that communication around the use of health data needs to be improved.

We continue to engage with the public to ensure accountability and raise awareness of the role of data in lasting benefits for the population’s health.

Glasgow, UK

Not so elementary, my dear Watson From Ray Hinks I see a possible connection between two articles in the same issue of New Scientist.

One reported an investigation

by Gabriele Doblhammer that found the rate of dementia to be 7 per cent lower among people born in Germany between December and February (17 October 2015, p 21). In the other,

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education researcher Stephen Gorard gave views on helping kids born in summer keep up at school (p 28). He mentioned that around 6 per cent more children born in England and Wales in the autumn gain five or more “good” exam grades at age 16, compared with those who are born in summer and go to school when younger.

It seems to me there could be a link between the two. Isn’t it time to set a computer such as IBM’s Watson the task of searching all knowledge to find such hidden links? I suspect this is now beyond the ability of a human polymath.

Townsville, Queensland, Australia

record collection and child’s toy would be at risk. Our world may have a lot of plastic waste, but once such organisms get going they won’t be able to tell the difference between rubbish and vital equipment.

Galway, Ireland

Sharp-eyed squid in a cloud of ink

Better ways to spend £100bn

From Michael Roger More than 20 years ago I read somewhere that a squid’s visual acuity is eight times that of humans. Ever since then I’ve wondered why.

Now I read that an inky cloud helps squid hunt (5 March, p 17).

Have ink and sharp-sightedness evolved hand-in-hand to provide optimum turbidity to hide and the keenest eyesight to see through it?

Vale, Guernsey, UK

From Brian Pollard Richard Ellam suggests the UK invests in electric cars instead of buying sea-launched nuclear weapons (Letters, 6 February) .

With £100 billion to spend, we could perhaps do even better.

Based on the cost of the Gemasolar 24/7 solar power station prototype near Madrid (11 December 2010, p 21) and assuming fourfold reduction in price per installed watt when building multiple, larger installations, the UK could produce its entire peak electricity demand using solar power stations in, say, the Sahara desert, plus a wind power component.

That would include installing superconducting cabling across the Mediterranean Sea. Electric cars would come down in price if sold in the same quantities as today’s vehicles.

A subsidy of just £1 billion to encourage their use would reduce the cost of a fleet of 100,000 cars costing £20,000 each by 50 per cent, after which the price would start to come down.

So with our £100 billion, we could have electric cars run off solar power, along with all our other electrical appliances at

Plastic-eating bugs: the horror!

From Rachel Cave Barry Cash suggests developing a plastic-degrading fungus to clear the oceans of waste (Letters, 12 March) and then you report work on bacteria that eat PET plastics (19 March, p 17). This should fill us with terror.

If that work were generalised, every plastic-sheathed electricity cable, plastic water pipe, plastic component of medical devices, kitchen appliance, plastic food or drink container, vehicle, fabric, laptop, phone, TV, DVD, vinyl

From Mike Eldridge Has Barry Cash not seen the 1971 film The Andromeda Strain, nor the 1970 episode of the UK TV series Doomwatch with plasticeating bugs? I wouldn’t be too happy if a fungus ate the hull of my glass-reinforced plastic boat.

Falmouth, UK

“ We’ll look back and laugh at the pseudoscience we believed about appetite and obesity” J ane Masters responds to our report that hunger hormones are similar at lunchtime even if you skip breakfast (26 March, p 39)

home and in factories – our entire electricity supply decarbonised.

Great Shoddesden, Hampshire, UK

Solar power from space at night From Eric Kvaalen Martin Greenwood rightly points out that the collecting station needed to catch microwave power from solar panels in space would take much more room than solar panels on Earth (Letters, 25 March). The only reason to put panels in space is to ensure a constant supply of power night and day, in fair weather and foul.

Les Essarts-le-Roi, France

An impossible criterion for theory From Tim Hopkins I was flabbergasted to read Jim Baggott and Daniel Cossins suggesting that one criterion for replacing the scientific method of experimental verification of Tom Gauld

predictions could be TINA: that “there is no alternative” to the theory (27 February, p 38). How can you ever be sure there is no alternative? This criterion is logically impossible to meet.

Rockville, Maryland, US

John Dee on Her Majesty’s Service From David Hulme Philip Ball’s article on John Dee, mathematician and magician to Queen Elizabeth I, in the wake of an exhibition at the Royal College of Physicians in London (27 February, p 48) reminded me that the exhibition curator, Katie Birkwood, was trying to find documentation of John Dee’s cryptic “007” signature.

The 007 is thought to be either a sacred numeral code, or a pair of eyes with the number 7 written around them – the seven supposedly representing his two eyes, his four other senses, and a seventh occult sense.

The obvious question is: is there a link between Dee and James

Bond? There is a story that when Ian Fleming visited Manchester Cathedral, where Dee had once been warden, he learned about the signature and adopted it for his character James Bond. Others say Dee – who may have gathered useful intelligence for the queen – was an inspiration for Bond.

Stockport, UK

Cyber-snow to Arctic peoples From Sam Edge Your report of malicious software holding medical records to ransom was interesting (27 February, p 26).

While ransomware is becoming a real nuisance, the proliferation of “threat intelligence” consultants is more of a danger to gullible organisations’ bank balances.

I have had the dubious pleasure of attending cybersecurity seminars presented by former UK police officers who, after having attended a few courses while on the public purse, go on to take private sector roles dishing out

blindingly obvious, or sometimes laughably misinformed, advice to naive management types, at eye-watering hourly rates.

Ringwood, Hampshire, UK

Shedding light on early data sending From David Murray Pipe Richard Ely reports using light to transmit data in 1968 (Letters, 13 February). While working at the General Electric Research Labs in 1958, another lad and I scraped the paint from Mullard transistors and used them, with the help of headlamp reflectors from my Morris 8 car, to communicate over the 30 metres between our labs.

Why? Chatting on the internal phone was frowned upon.

London, UK From Dennis Wort Reading Nicola Jones’s article on light-based communication (9 January, p 30) reminded me that the German army had an experimental photophone in the 1940s. This worked by so-called frustrated total internal reflection: the audio signal varied the very small spacing between a right-angled prism and a sheet of glass backed with an absorber.

Whitby, North Yorkshire, UK

For the record n Roxana Hickey and James Meadow were both postdoctoral researchers at the University of Oregon when they experimented on identifying people by microbe haloes (5 March, p 38).

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FEEDBACK

Paul McDevitt

For more feedback, visit newscientist.com/feedback

OUR colleagues missed out on the story of the century earlier this month, when the Mail Online revealed that a “Martian researcher” had discovered a door in the sun, leading

Nor can Feedback imagine why NASA has so far chosen not to promote its Earth-shattering discovery. Perhaps the space agency has a lucrative sideline in collecting

to a hollow interior.

A recently published image from NASA’s Solar and Heliospheric Observatory showed a bright line across the face of Earth’s nearest star, reminiscent of an imaging artefact.

tolls from galaxy-hopping aliens on their way to this solar bolthole.

Liberatore closed her article on alien-made hollow suns with a ufologist’s earnest proclamation that “It can happen, and probably

Alternatively, as journalist Stacy Liberatore put it: “This picture suggests that the theory our sun is hollow and houses ‘a massive world 1,000 times our own inside’ has been true for millions of years.” The gigantic door, we are told, is needed for aliens

already has” – a sentiment shared

by Feedback when imagining what fruitloopery might be published next.

to access the sun’s cavernous interior.

Why the Mail thought that Mars researchers would have their telescopes focused on the sun instead of the Red Planet isn’t clear, though we expect that Daily Express journalist Jon Austin – who has chronicled the discovery of various unlikely objects on Mars, including a fossilised baby (13 February) – must feel as though he has been scooped.

READERS may recall PLoS One grappling with an errant paper in which the authors credited the biomechanics of the hand to “proper design by the Creator” (New Scientist, 12 March, p 7).

You’d be forgiven for thinking this would put scientists off making allusions to God for a while. Yet Discover’s Neuroskeptic blog noticed four study authors doing just that, declaring in their review on solar stills that “Water is a gift from God”.

Andy MacQueen is informed that his new lamp can be “attached to any surface classified as normally inflammable”. How thoroughly does one test such a condition?

56 | NewScientist | 9 April 2016

PREVIOUSLY, Peter Davies argued that socks exist in quantum superposition, by virtue of being both left and right-footed simultaneously, only

Cross – particularly as this titan of history died after a particularly heady drinking session.

collapsing into one orientation when you put them on.

Crispin Piney provides further evidence of the quantum nature of socks. “They are also entangled,” he writes, “not only when coming out of the washing machine, but also in a quantum sense.” The moment one is put on and has its polarity set, “the other one immediately adopts the complementary value”.

What then should Feedback make of trousers which, like particles in a

SPEAKING of measures, “If ever a band’s name was a product of its time, it must have been 10cc,” says Colin Smythe. “What could it call itself now? 10mL doesn’t have quite the same ring to it.”

Nor does Twenty Three Centimetre Nails, we think.

vacuum, always emerge as a pair?

published online tempers this advice with the reminder that “laser pens under 1 megawatt are safe and legal”.

“So I only need to worry about somebody shining a 1-gigawatt laser at me?” wonders Peter Verity. “This sounds like Ronald Reagan’s star wars all over again!”

UNLESS he works in a nuclear plant, “Mick Johnson will never encounter nuclear electricity”, writes Kevon Kenna (19 March).

“It only gets as far as the first transformer, where the nuclear electricity in the transformer primary induces ordinary electricity in the secondary.”

Does this mean Feedback can remove the lead cladding from our junction box?

UK BUSINESS minister Anna Soubry called on trading standards officers to shut down rogue vendors selling dangerous lasers to children. A memo

MORE unusual uses for New Scientist magazine: Paul Stapleton informs us that he always keeps a few copies in his car, to while away the time spent motionless in traffic jams.

“One day I ran out of petrol, and a rolled-up copy of the magazine formed an excellent funnel to pour some fuel into the filler tube without drenching the paintwork and my shoes. I finished reading the issue with a fire extinguisher close at hand.”

Please don’t try this at home, says Paul… to which Feedback adds: please don’t try it anywhere else, either.

IN CONNECTICUT, boat owners are encouraged to make waves.

Brunello Nucci sends evidence from a sign in his local marina that warns boaters: “You are responsible for your wake. Careless or reckless operation strictly enforced.”

A 750-megalitre bottle of wine (19 March) has to be called an Alexander the Great, thinks Frank

FEEDBACK has often noted how unusual units are commandeered for illustration purposes – such as expressing the fuel expenditure of a Saturn V rocket in elephant masses. Rebecca Donnelly forwards a video that takes this idea to its literal conclusion, with an animated Saturn V rocket ejecting 3.16 elephants per second as it climbs into the sky. Watch it yourself at bit.ly/ns-boost.

You can send stories to Feedback by email at feedback@newscientist.com.

Please include your home address.

This week’s and past Feedbacks can be seen on our website.

Last words past and present at newscientist.com/lastword

THE LAST WORD Long in the tooth My dentist says that dental enamel is never replenished and we have to make do with the adult set of teeth throughout our grown-up lives.

I can’t believe that after some 80 years of chomping and grinding, my teeth are still the same shape, without apparent signs of wear.

Is he right? If so, why am I generally still toothily intact?

n Despite the best efforts of your dentist, there is no regenerating lost enamel.

By the time a tooth erupts through the gum, its enamel formation has ceased and it will have no further contact with the cells capable of repairing or remodelling it. So it is fortunate that the tooth’s outer enamel layer is, in fact, the hardest tissue in the body. It is 96 per cent hydroxyapatite crystals by weight, the remainder being organic material and water.

Loss of this crystalline structure occurs in three main ways: attrition, the wear of enamel through tooth-to-tooth contact, such as grinding; abrasion, by external agents such as a hard-bristled toothbrush; and erosion, the demineralisation of the enamel crystals by acids.

Such acids can come from foods like fizzy drinks or citrus fruits, although stomach acid in those who experience gastric reflux can also be a culprit. Tooth decay results from a breach of the enamel due to acids produced by the bacteria in our mouth

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when we feed them sugars.

As a result of all these processes, enamel will inevitably wear with age, although with due care and attention this can be kept to a minimum.

It is worth noting that fluoride applied to the surface of the teeth can strengthen enamel and make it more resistant to wear, but there is nothing available at the moment that can replenish lost enamel.

Stuart Yeaton Oral and Maxillofacial Surgery Department Barnet General Hospital, London, UK

attrition takes place. Over the course of our lives, therefore, the teeth are not in contact for much of the time and so wear and tear is minimal.

However, under psychological stress, tooth grinding and clenching can lead to excessive wear. One common source of extreme wear is bruxism, the unconscious grinding of the teeth while we are asleep.

Philip Taylor Retired dental surgeon Kinloss, Moray, UK

n Tooth enamel is never replenished because the ameloblast cells that form the enamel are on the surface of the developing tooth. These cells are destroyed when the tooth erupts into the mouth.

Tooth enamel (calcium hydroxyapatite) is the hardest material in the body. By contrast, the Western diet is generally very soft and rarely contains any abrasive materials. Consequently very little attrition occurs during whatever minimal chewing is needed. What’s more, under normal conditions, teeth only fully come into contact with those in the opposing jaw when we swallow. During chewing, food in between the teeth reduces tooth-to-tooth contact.

Between meals, when the jaw is at rest, there is normally a gap of 2 to 3 millimetres between the teeth – the freeway space – so no

I read in New Scientist that the pressure at Earth’s core is 3.6 million atmospheres. I would expect the pressure there to be zero, because it arises from gravity, and this must be zero at the core since the pull of the surrounding matter is equal in all directions. Can someone get to the bottom of this?

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Unanswered questions can also be found at this URL.

Question Everything

Under pressure

n Don’t confuse the pressure at any point with the gravity at that point. Certainly the gravitational forces at the centre of mass cancel out, reducing weight to zero. But the gravity at every other point inside Earth is directed towards the centre of mass, increasing the pressure at all deeper points.

Imagine a tightly inflated elastic balloon: the gas at the centre is under high pressure, even though that pressure is applied only around the outside.

Jon Richfield Somerset West, South Africa

n The pressure at the bottom of the Mariana trench in the Pacific Ocean is more than 1000 atmospheres. If we were able to find a trench elsewhere that was twice as deep, the pressure there would be more than double that.

Keep going down further, and the pressure keeps going up.

At the very centre of the Earth, the pressure is caused by the weight of about 6400 kilometres of liquid iron and rock lying above.

Just because gravity is zero at Earth’s centre doesn’t mean that the stuff overhead has suddenly become weightless. Imagine the heavy column of molten rock below Singapore that bears down on the core. On the other side of the globe, the weight of the molten column under Ecuador pushes down in the opposite direction.

An object at the centre of Earth’s core may be weightless, but it is like an orange pip being squeezed between your fingers.

Hugh Hunt Cambridge, UK

This week’s question Green genome

If we could somehow splice the recipe that plants use for making chlorophyll into our genes, could we then satisfy some of our energy needs by photosynthesising?

Sophie Holroyd Bromyard, Herefordshire, UK

The latest book of science questions: unpredictable and entertaining. Expect the unexpected Available from booksellers and at newscientist.com/questioneverything