The nature-nurture debate remains a hardy perennial for parents: why are siblings so ­different to each other? The latest evidence makes it look increasingly likely that genes play little or no part. Many naturally incline to the cosy answer that “it’s a bit of both” but the evidence I presented eight years ago in my book They F*** You Up already showed that, even if you accepted the validity of studies of identical twins (which I do not) on which nearly all claims about the role of genes were based, they did not ­support this idea. For the vast majority of common traits, such as sociability, memory or creativity, heritability was closer to a quarter.

Then came the findings of the Human Genome Project in 2001. To the horror of geneticists, Craig Venter, one of the main researchers, pointed out that the fact that we only have about 25,000 genes meant psychological ­differences between individuals could not be much determined by them – “our environments are critical,” he concluded.

Initially, geneticists disputed this, but the last decade has seen an increasingly rapid retreat. After many millions of pounds and thousands of studies, attempts to identify genes that have much effect on our psychology have failed. The most distinguished researchers now admit that it is ­extremely unlikely that there are single genes for major mental illnesses such as schizophrenia. After decades of hearing from such people that there would be a gene for almost everything, I admit to having felt a twinge of smugness.

Their fallback position is that it’s lots of different genes interacting together that matters, but that much remains to be seen. And now comes the first sign that the geneticists may eventually have to admit defeat.

This month’s editorial of the Journal of Child Psychology and Psychiatry is entitled “It’s the environment, ­stupid!“. The author, Edmund Sonuga-Barke, confesses that “serious science is now more than ever focused on the power of the environment… all but the most dogged of genetic determinists have revised their view of the primacy of genetic factors.”

In Sonuga-Barke’s own field, ADHD, he states that “even the most comprehensive genome-wide scans ­available, with thousands of patients using ­hundreds of thousand of genetic ­markers … appear to account for a relatively small proportion of disorder expression.” In plain English, genes hardly explain at all why some children have ADHD and not others.

Another fallback is to claim that genes create vulnerabilities that environments may or may not cause to be expressed. This position took a massive blow at the end of last year. Some studies had shown that people with a particular gene variant were more likely to become depressed if they were maltreated as children: the variant created a vulnerability. This was all but disproved.

An analysis of the 14,250 people whose DNA had been mapped in 14 studies showed that those with the variant were not at greater risk of ­depression than those without it. Nor were they more likely to be depressed when the variant was combined with childhood maltreatment

In Darwinian terms, it has always made much more sense that we should be born plastic. Obviously, genes confer fundamentals, such as the capacity for humour or anger, but how much and how we express these is in response to our particular family situation, for which we need flexibility, not predetermination. If genes play little part in how our children turn out, that is incredibly good news. Unlike our DNA, we can do something about them.

Source: The Guardian –