MATT RIDLEY'S NEW book is the fulfilment of an implicit promise. In an earlier book, Genorne, he had proclaimed himself to be no genetic determinist, arguing that the evidence points the other way. 'The more we delve into the genome', he wrote, 'the less fatalistic it will seem.' His confidence might seem to have been misplaced, given recent scientific developments. Giant strides have been made in understanding the roles played by individual genes in crucial matters including particular diseases and forms of behaviour, discoveries which lend powerful support to champions of nature in the nature-nurture debate.

In this book Ridley takes up the challenge to dlsprove genetic determinism, the view that our genes dictate everything about us and our lives. But he also sets out to dsprove the opposing claim, whlch is being voiced afiesh by nurture's defenders now that the completed mapping of the human