Why we are who we are

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NATURE VIA NURTURE

Matt Ridley

Fourth Estate, 18.99

ACCORDING to Matt Ridley, the writing was on the wall for the nature-nurture debate from the moment Watson and Crick worked out the double-helical structure of DNA. Fifty years of molecular genetics mean we can now understand gene function as a chemical process. As our bodies are biochemical machines, it stands to reason that the regular chemical hurly-burly within each of our cells will affect how our genes express the information contained within them.

In the new genetics, the genome is more than a static book of instructions: it is a colossal bank of switches that can be turned on and off by other genes and environmental stimuli. Genes are schooled by life and learn its lessons, just like the organisms whose learning they make possible.

Nurture gets to work on nature, and nature makes organisms seek out specific nurtural influences. The nature-nurture dichotomy was always a false one: you can’t have a brain without the genes that oversee its construction, and a brain that cannot respond to experience is not much of a brain at all.

Take love, for example. Two kinds of vole which differ markedly in their attitude to lifelong loving - one is a loyal pair-maker, the other a footloose polygamist - turn out to differ in their expression of oxytocin-receptor genes. But love must take an object, and the romantic vole will be lost unless the environment presents it with a partner. Genes can wire us up for romance, but nurture must finish the job. This account leaves many questions unanswered, not least how oxytocin-inspired attraction is directed towards one vole rather than another.

Some of this ground has already been covered by Steven Pinker, whose recent The Blank Slate casts a long shadow over Ridley’s book. Ridley, it is safe to say, does it better. In his hurry to demolish the "blank slate" conception of human nature, Pinker trampled over vast swathes of learning about humanity, not least the idea that experience and culture, far from being utterly reducible to the action of our genes, have an important role to play in shaping that action.

Ridley realises that what we really need are some new ideas about how genes and environment interact in building brains and organisms, and he offers much in the way of promising hypotheses.

The nature-nurture debate, of course, was driven by headlines: "Scientists discover gay gene"; "Only 30,000 genes in the human genome". Ridley shows courage in rising above the clamour for soundbites and resolutely telling the story in all its complexity. He does so in exceptionally well-crafted prose, producing a book as inspiring as it is impressive.

Charles Fernyhough is a novelist and psychologist