The power and fascination of Are We Hardwired? lie in their explanation of that deceptively simple answer. Using eye-opening examples of genetically identical twins who, though raised in different families, have had remarkably parallel lives, the authors show that indeed roughly half of human behavior can be accounted for by DNA. But the picture is quite complicated. Clark and Grunstein take us on a tour of modern genetics and behavioral science, revealing that few elements of behavior depend upon a single gene; complexes of genes, often across chromosomes, drive most of our heredity-based actions. To illustrate this point, they examine the genetic basis, and quirks, of individual behavioral traits -- including aggression, sexuality, mental function, eating disorders, alcoholism, and drug abuse. They show that genes and environment are not opposing forces; heredity shapes how we interpret our surroundings, which in turn changes the very structure of our brain. Clearly we are not simply puppets. Perhaps most interesting, the book suggests that the source of our ability to choose, to act unexpectedly, may lie in the chaos principle: the most minute differences during activation of a single neuron may lead to utterly unpredictable actions.

This masterful account of the nature-nurture controversy -- at once provocative and informative -- answers some of our oldest questions inunexpected new ways.