PS RATING: B-
Chang and Eng, the first documented Siamese twins, shared a body and all its genes. They were raised in an identical environment, yet their personalities differed to extremes that sometimes led them to haul off and punch each other. One was passive and sober, the other aggressive and drunk. Now, more than a century after their death, their story illustrates the still-growing debate over what determines who we are: our biology, our environment, or both.
And now, a slew of new books is adding fuel to the nature-versus-nurture fire. The Misunderstood Gene and The Cooperative Gene lean toward the nature side, while The Dependent Gene argues for a middle ground. Another, What Evolution Is, takes the nurture position. But in Human Natures, Stanford biologist Paul Ehrlich—author of the 1968 blockbuster The Population Bomb—argues that both extremes of the debate are flawed.
With five decades of research and more than 4,000 references and notes, Human Natures is an impressive introduction to evolutionary biology, but that was not Ehrlich's goal. He wanted to turn the nature-nurture debate on its head. For instance, he claims the whole concept of human nature is wrong, because there's not one but many. What determines some tendencies—like the desire to eat and have sex—is biological evolution, he says, while others, such as violence, religion, and art, are influenced by cultural evolution, which he never clearly defines but sees as the missing ingredient in the ongoing debate.
Ehrlich's connections and arguments aren't always clear, but he comes at them with admirable goals: He hopes to prove that there's no scientific basis for racism, sexism, war, and other human ills. Unfortunately, his discussion of cultural evolution is so vast and hazy that the book quickly spirals into unleashed wanderings through Ehrlich's brain. As a result, the only thing turned on its head is the reader.