Matt Ridley: What switches the genes on and off

In his latest book, popular science writer Matt Ridley--author of Genome and The Red Queen-- explores some of the social and philosophical implications of the rapid new developments taking place in our understanding of how human genes function.

"Everyone has always known that we are a mixture of nature and nurture, but the debate is always framed as though they are pulling in opposite directions. Now the more we look into genes--and we've moved on from genetic diseases to genes that affect the mind and behaviour--the more we begin to see a mechanism by which both nature and nurture are involved. Genes are simply devices for extracting experience from the environment.

"The FOX P2 gene, newly discovered in Oxford, seems to be absolutely essential to the ability to learn language--without the human version of this gene, you can't extract the rules of syntax and grammar from the mess of sound you hear around you during your formative years of life. But if you deprive a child of exposure to speech for their first 12 or 13 years of life, they will never be able to learn language. So there needs to be nurture there as well.

"That's just one example of many such genes that we're now beginning to understand, whose actions are literally switched on and off by experience in some cases.

"I am trying to steer the debate towards people on the nurture side being much happier about admitting the involvement of genes. The reaction to twin studies [research showing deep similarities in the personalities of identical twins reared apart] has been on the whole to wish them away, to try to find holes in the methodology and biases in the motivation of the people who conducted them. But twins reared apart really do show us that the variation we see about us in personality has a lot more to do with our internal make-up than how we were brought up by our parents. That's not to say that bringing up children badly can't affect personality, clearly it can.

"Late in the writing of this book an extraordinary study came out of University College London about a particular gene. Having a low active version of this gene predisposes you to a life of crime and antisocial problems--if and only if you also get a somewhat abusive and neglectful childhood. Now that seems to me an extraordinary discovery: you can actually take a child who has already suffered from abuse, and according to which version of this gene the child has got, it will either be OK despite the neglect, or it will not be OK and therefore we will have to focus our attention on trying to rescue that child.

"We now know that remembering something that happened 10 minutes ago involves genes as well. When you remember a telephone number it switches on or off a gene inside your brain which alters the strength of connections between brain cells. Which makes genes much less frightening because they are downstream of behaviour, not upstream. The significance of this has not yet dawned on the philosophers. Deep in the biological laboratories they are coming up with things which are of huge relevance to the way that everyday people think about the world."