The myth of genetic determinism

Marita Kimo

The myth of genetic determinism

Frankie Langeland

There is a pervasive belief that individual genes can determine complex behavioural traits such as intelligence, aggression, and susceptibility to mental illness. This is not supported by evidence and shows a fundamental misunderstanding of how genetics work. Many findings in science will never make the pages of the British tabloids but genetic behavioural studies are different. These results are about who we are and what makes us act the way we do – a big draw for readers and a sure sell for the press.

The media constantly reports the myth that single genes determine behaviour, but the relationship between genetics and behaviour is complex and mediated by many different genes.

‘despite claims, it is not possible to test for specific genes’

A quick google search before I begin to write reveals several articles which this falsehood. One headline, ‘Scientists Find Suicide Gene’ forgets to mention that the study in question actually found hundreds of potential genes for future suicide investigations. Current studies do not look at genes in isolation, but scan whole sets of DNA to look for potential genetic influences on behaviour. This requires an extremely large sample size, sometimes using over a million participants. Even then only common genetic variants are detected and these tend to show very weak effects. A study may find that ‘gene X influences trait Z’ but this influence is small and there are other factors which impact our behaviour, including our environment.

Yet the press maintains a stance of genetic determinism and this has an impact outside of public awareness. In China whole industries have emerged that exploit these misconceptions. Hundreds of ‘genetic talent detecting agencies’ offer to screen a child’s DNA to reveal their supposed ‘genetic gifts’. Thousands of parents have already tested their children to see if they should be pushing a future in mathematics or music. These companies claim to profile characteristics such as IQ, emotional understanding, and extroversion.

Despite the claims of these companies, it is not possible to test for specific genes that cause mathematical genius or musical talent, nor can we test for intelligence or personality. Associations chalked up to parents as having a deterministic influence, like the misleading stories presented in the press, when in reality these measures are crude. Controversially, researchers at Chinese universities are benefiting from these companies as they buy the data extracted for their research. It’s ironic that the data used by researchers trying to increase knowledge comes from companies whose profit relies on that knowledge being suppressed.

‘there are few traits that have binary genetic influence’

Perhaps more importantly, the genetic determinism myth has infiltrated our criminal justice systems. In 2006, Bradley Waldroup violently murdered his wife’s friend, Leslie Bradshaw and repeatedly attacked his wife. His wife survived but Leslie did not. Waldroup admitted to both murder and attempted murder - the prosecution were confident of a guilty verdict. Yet, after 11 hours of deliberation the jury came back with a unanimous ‘not guilty’ verdict. During the trial defence lawyers had ordered a test showing Waldroup had a genetic variant which produces the enzyme Monoamine Oxidase A (MAO-A) known as the ‘warrior gene’. Individuals with this variant have been shown to exhibit antisocial impulses and extreme violence. Waldroup’s lawyers were able to convince the jury that it had been the warrior gene’s influence which caused the murder with one juror stating “a diagnosis is a diagnosis, it’s there. A bad gene is a bad gene.”

There was some truth in the defence’s case; MAO-A has been associated with antisocial behaviours but only in individuals of European descent who were also abused in childhood. The gene does not cause violent behaviour without an environmental influence. Many individuals in the criminal justice system have had abusive childhoods and have still been found guilty for their crimes. MAO-A has also been linked to gambling, depression and irritability. Whilst the warrior gene sounds more dramatic than the irritable gene when reported in the press, the name is glamorised and unhelpful in elucidating the public. Most importantly, 34% of Europeans have the warrior gene yet we do not see 34% of individuals committing murder – genes alone do not drive behaviour.

‘whole industries have emerged that exploit these misconceptions’

The prevalence of this myth is having real impacts. Whilst the media maintains public misconceptions of genes it may not be the root of the problem. The education system also teaches children about genetic determinism. Up and down the UK pupils learn about Mendel and his peas; a simplistic introduction to inheritance that suggests genetic influences are all or nothing. There are few traits which have a binary genetic influence (eye colour being one of the exceptions). Most genetic effects are much more complex, and a failure to appreciate this complexity that may lead us astray.

The public are being misled because the truth about genetic behavioural studies is deemed either too boring or too difficult. However, many exciting and relevant studies are taking place all the time - including here at the University of Bristol where links between genetics and online behaviour are being investigated. Behavioural genetics has the potential to be misapplied, but it is also a tremendously exciting avenue of research. We should not let the complexity allow us to be inappropriately reductionist in reporting these findings.