"Nature versus nurture" sums up in a nutshell one of the most contentious debates in science: Are people's qualities determined by their genes (nature) or by their environment (nurture)? The debate has only grown louder since the human genome has been found to comprise only 30,000 genes. Some scientists claim that we don't have enough genes to account for all the existing human variations. Ridley, author of the bestseller Genome,
says that not only are nature and nurture not mutually exclusive, but that "genes are designed to take their cue from nurture." Genes are not unchanging little bits of DNA: their expression varies throughout a person's life, often in response to environmental stimuli. Babies are born with genes hard-wired for sight, but if they are also born with cataracts, the genes turn themselves off and the child will never acquire the ability to see properly. On the other hand, stuttering used to be ascribed solely to environmental factors. Then stuttering was found to be clearly linked to the Y chromosome, and evidence for genetic miswiring of areas in the brain that manage language was uncovered. But environment still plays a role: not everyone with the genetic disposition will grow up to be a stutterer. Ridley's survey of what is known about nature-nurture interactions is encyclopedic and conveyed with insight and style. This is not an easy read, but fans of his earlier book and readers looking for a challenging read will find this an engrossing study of what makes us who we are. (May 1)
