Comparing the World Zones

Comparing the World Zones

Lecture 36

The ice age continent of Sahul included modern Australia, Papua New Guinea, and Tasmania. It was uni ed because lower sea levels at the height of the last ice age lled the bridges between these areas—so, it was a single landmass.

How typical was Afro-Eurasia of the sort of historical changes that occurred in other parts of the world? To answer this question, the next two lectures survey developments in the American, Australasian, and Paci c world zones. At rst sight, what stand out are the huge differences between these different worlds. But as we look more carefully, we will also begin to see some surprising and important similarities.

Comparisons between world zones are important for two main reasons. First, the differences mattered. They shaped the diverse histories of each region; but they also shaped the history of the world as a whole in the last 500 years, since the coming together of the world zones. Second, if we nd important similarities between the zones despite the lack of signi cant contact between them, this may hint at some deep patterns in human history as a whole.

Here, I will summarize information on the early history of the various world zones. During the ice ages, modern Australia, Papua New Guinea, and Tasmania were united within the continent of Sahul. The Australasian zone was smaller in area than the Afro-Eurasian or American zones, and less diverse, with relatively arid climates and at landscapes (except in modern Papua New Guinea). Its soils were old and relatively infertile. Sahul inherited the marsupial fauna of the supercontinent of Gondwanaland, of which it was a fragment, but it had separated from Gondwanaland almost 100 million years ago, so its plant life and animal life were quite distinctive. The human history of Sahul began 40,000 to 50,000 years ago, during the last ice, when it still formed a single continent. To reach Sahul from Outer Eurasia, humans had to cross at least 60 kilometers of open sea and adapt to entirely new ora and fauna. No other large mammal made this crossing, so it provides clear evidence of our ancestors’ unique ecological adaptability. Megafaunal

extinctions and the widespread use of restick farming demonstrate that even where agriculture did not appear, humans could have a signi cant impact on their environments.

The American world zone formed just 3 million years ago, when a large fragment of the supercontinent of Laurasia (North America) touched a large fragment of Gondwanaland (South America) at the isthmus of Panama. As a result, this zone (uniquely) stretches from the Antarctic to the Arctic and spans all major ecological and climatic zones. As Jared Diamond has pointed out, this north-south orientation means that when humans arrived they found that most migrations led them into new and unfamiliar environments, in contrast to Afro-Eurasia, where it was possible to migrate huge distances east or west while remaining in regions of roughly similar climate and ecology. Did the north-south orientation of the Americas slow the pace of change here? Humans entered the Americas from East Siberia, certainly by 13,000 years ago and maybe several millennia earlier. As in Sahul, the sudden entry of humans into unfamiliar territory may help explain the massive megafaunal extinctions. The removal of so many large species of mammal may have had a signi cant impact on American history because it meant that there could be no American equivalent of the “secondary products revolution.”

The Paci c world zone formed a huge island archipelago whose communities were separated by hundreds or thousands of miles of open sea. Each island had distinctive features and therefore a distinctive history. But all (except New Zealand) were small. (As Jared Diamond has pointed out, the diverse ecologies of different Paci c islands set up a wonderful series of natural experiments in the impact of environment on human history.) The Paci c world zone was not occupied until the later Agrarian era. It was settled by migrants who brought knowledge of farming and superb navigational skills. It used to be assumed (for example, by Norwegian scholar and adventurer Thor Heyerdahl) that the Polynesians came from the Americas. However,

Estimates of the population of the Americas 500 years ago range widely from about 40 million to as high as about 100 million.

the similarity of their Austronesian languages, and the spread of a distinctive type of pottery (Lapita ware), has shown that the Paci c islands were settled by people whose ancestors probably came from the mainland of Southeast Asia. The islands of Melanesia (to the east of Papua New Guinea, reaching as far as Fiji and Tonga) were settled over tens of thousands of years by migrants traveling in huge, oceangoing double-hulled canoes, carrying taro, yam, breadfruit, coconuts, and sugarcane as well as chickens, dogs, and pigs. The remoter islands of eastern Polynesia were mostly settled during the 1st millennium C.E. New Zealand, one of the last regions to be settled, was probably colonized between 1000 and 1200 C.E.

How did the agricultural revolution play out in each of these zones? In the Australasian zone, agriculture appeared early, but only in modern Papua New Guinea. In Papua New Guinea, agriculture was based on root crops such as taro that did not store well, which may be why no Agrarian civilizations emerged here. However, there did emerge ourishing and highly competitive “early Agrarian” village communities, which have survived to the present day. Agriculture ourished because Papua New Guinea was at the leading edge of the Australian tectonic plate as it plowed north so that, unlike other parts of Australia, its landscapes were warped to form a great variety of different soils and terrains. In Australia and Tasmania, landscapes were older and atter, and soils were poorer. Foraging technologies survived to modern times. However, even in Australia there was signi cant change within recent millennia. Indeed, in some regions there appeared semi-sedentary communities that are reminiscent of the af uent Natu an foragers of the Fertile Crescent 12,000 years ago. By 500 years ago, when the world zones would at last be joined, the population of Sahul cannot have been more than about 2 million.

In the American zone, agriculture evolved later than in the Afro-Eurasian zone, and in different ways. Though maize and squashes may have been cultivated earlier, the earliest dated samples of domesticated maize were grown about 3500 B.C.E., in the Tehuacán valley southeast of Mexico City. In South America, guinea pigs, llamas, and alpacas were domesticated by 2000 B.C.E. The relatively late development of cultivation in the Americas may re ect the absence of “easy” domesticates. Crops such as maize had to undergo signi cant changes before they could support large populations,

and many large mammals had been driven to extinction. Estimates of the population of the Americas 500 years ago range widely from about 40 million to as high as about 100 million. In the Paci c zone, migrants brought agricultural technologies with them. However, on some of the smaller islands, including Easter Island, agriculture eventually failed, leading to a return to modi ed forms of foraging. The total population of the zone is unlikely to have exceeded 1–2 million.

We have seen some striking differences in the historical trajectories of the different world zones, including a very signi cant demographic imbalance. Five hundred years ago, populations ranged from about 400–500 million in Afro-Eurasia to 50–100 million in the Americas, to just 1 or 2 million in the Australasian and Paci c zones. Nevertheless, there are also important similarities. In each zone, human numbers increased as innovations allowed humans to extract more resources from a given area. Even in Australia, populations increased signi cantly in recent millennia. So differences in the histories of each region were at least in part a matter of timing rather than of substance. Many of the differences re ect differences in natural endowment, in the size of local populations, and therefore in the “synergy of collective learning” in each region. Differences in the pace and timing of change would matter profoundly when the four zones were nally joined in the last 500 years.

We have seen that, despite important differences, there were also striking parallels in the histories of the four world zones. The most important was a universal long-term trend toward “intensi cation”: innovation characterized by the possibility of larger populations per given area and increasing complexity.

Essential Reading

Supplementary Reading

Questions to Consider

Bentley and Ziegler, Traditions and Encounters, chaps. 6, 21. Christian, Maps of Time, chap. 10. Diamond, Collapse ———, Guns, Germs, and Steel.

Bellwood, The Polynesians. Flood, Archaeology of the Dreamtime. Mann, 1491.

1. What were the most important geographical differences between the four major world zones?

2. How did geographical differences shape the histories of the four major world zones?