IDENTICALLY DIFFERENT

Genes dictate our anatomy, emotions and behavior, except when they don’t, according to this ingenious account of how inheritance and environments—including our parents’ environment—vie to make an individual.

Physician and TV commentator Spector (Genetic Epidemiology/King’s Coll. London; Your Genes Unzipped, 2003) fills his book with entertaining anecdotes of identical twins (he is director of the world’s largest twin registry) and examples from popular culture to make a convincing case that inheritance is more complicated than we think but no less fascinating. The idea that genes make us what we are ruled for half a century, until the 1960s, when a revolutionary generation insisted that our environment makes us what we are. Nowadays, scientists agree that both have an influence, but Spector cautions that DNA does not hardwire our lives. It turns out that actions can physically alter genes and that—despite what we learned in biology class—we can pass acquired traits to our children or even grandchildren. This process, epigenetics, means, for example, that a person who overeats transmits the risk of obesity for several generations. Genetics turns up in surprising places. Identical twins raised apart have remarkably similar personalities, sharing qualities such as optimism, empathy and a sense of humor (or lack thereof). Environmental factors also deliver plenty of surprises. Most readers will squirm to learn that upbringing exerts remarkably little influence on how children turn out. They are far more likely to emulate their friends than their parents, however competent and loving. Abusive parents are a different matter; crime, abusive behavior and mental illness have a disturbing tendency to run in families.

A delightfully thought-provoking overview of the nature-vs.-nurture debate.