DNA: the secret of life by James Watson with Andrew Berry

Can one molecule shape our personalities?

This book's title was inspired by James Watson's erstwhile collaborator, Francis Crick, who came bounding into the Eagle pub in Cambridge one Saturday afternoon in February 1953 announcing that the two scientists had just discovered the secret of life. Fifty years later, the boast seems only too real, given that the discovery of the DNA double helix has led to nothing short of a revolution in biology, medicine, anthropology and even forensic criminology.

Watson gained notoriety in 1968 with a highly personal, and extremely readable, account of the events leading up to that discovery in his book The Double Helix. Although he upset some people at the time with his rather idiosyncratic recall of what happened, The Double Helix became one of the greatest works of science writing in the late 20th century.

What is less well-known is Watson's equally brilliant foray into serious (by that I mean academic) science writing. Many an undergraduate has benefited from his seminal textbook, The Molecular Biology of the Gene, which has gone through numerous editions since 1965, and to this day remains essential reading for any serious student of biology.

Here, Watson combines the two oeuvres. He liberally sprinkles personal anecdotes and thoughts with an ambitious attempt at explaining the difficult science of genetics. The result is an unashamed eulogy for DNA, the complex molecule of inheritance which plays a central role in shaping our destiny.

Watson and his co-author start with the early history of genetics, from Gregor Mendel, the first to find evidence for the existence of genes, to the sterilisation campaigns of the 1920s and the doctrine of racial purity that was practised so ruthlessly by the Nazis. It immediately becomes apparent that no discussion of DNA and genetics can avoid the ethical and moral dimension.

We are accustomed to the idea that genes determine or at least influence many physical characteristics, but what about those facets of human behaviour and psychology that make us who we are? "The finding that there is a substantial [genetic] component to our behaviour should not surprise us; indeed, it would be far more surprising if this was not the case," says Watson.

The hoary old debate about IQ and genes is perhaps the prime example of the rancour that can contaminate the study of behaviour and genetics. Various studies showing that the heritability (a much-misunderstood measure of inheritance) is high for intelligence have been extrapolated to explain the supposed differences in IQ between social classes and racial groups.

Racists have used these heritability studies to justify their bigotry – a disturbing parallel to the way that Nazis used pseudo-science to justify their racial purity programme. Watson explains how heritability cannot be used to make sweeping conclusions, although he seems to keep an open mind on racial differences: "The idea of measurable variations in average intelligence among ethnic groups is not one, I admit, I want to live with."

No matter how apparently strong an influence genes play in shaping our personalities, it is the environment, our education and upbringing, that really matters. As Watson admits, "We are not mere puppets upon whose strings our genes alone tug."