Darwin recognized more than 100 years ago that Homo sapiens evolved by the same process as every other species on earth. And philosophers such as William James were eager to apply Darwin’s insights to human psychology. But during the first part of this century, the rise of ““social Darwinism’’ (a non-Darwinian, sink-or-swim political philosophy) and later Nazi eugenics spawned a deep suspicion of biologically inspired social science. By 1954, anthropologist Ashley Montagu was declaring that mankind has ““no instincts because everything he is and has become he has learned, acquired, from his culture.''
The distinction between innate and acquired seems razor sharp, until you try slicing life with it. Consider the development of the brain. While gestating in the womb, a child develops some 50 trillion neurons. But those cells become functional only as they respond to outside stimuli. During the first year of life, the most frequently stimulated neurons form elaborate networks for processing information, while the others wither and die. You could say that our brains determine the structure of our experience – or that experience determines the structure of our brains.
Social behavior follows the same principle. From the old nature-versus-nurture perspective, a tendency that isn’t uniformly expressed in every part of the world must be ““cultural’’ rather than ““natural.’’ But there is no reason to assume that a universal impulse would always find the same expression. As the evolutionists John Tooby and Leda Cosmides have observed, biology can’t dictate what language a child will speak, what games she’ll play, what rites she’ll observe or what she’ll feel guilty or jealous about. But it virtually guarantees that she’ll do all of those things, whether she grows up in New Jersey or New Guinea.
Biology, in short, doesn’t determine exactly what we’ll do in life. It determines how different environments will affect us. And our biology is itself a record of the environments our ancestors encountered. Consider the sexes’ different perceptual styles. Men tend to excel at spatial reasoning, women at spotting stationary objects and remembering their locations. Such discrepancies may have a biological basis, but researchers have traced the biology back to specific environmental pressures. Archeological findings suggest that men hunted, and women foraged, throughout vast stretches of evolutionary time. And psychologists Irwin Silverman and Marion Eals have noted that ““tracking and killing animals entail different kinds of spatial problems than does foraging for edible plants.''
Unfortunately, a trait shaped by one environment can become deadly in another. Craving fat, and storing it efficiently, would promote survival in a setting where food sources were scarce and unpredictable. But the same tendencies cause mass heart failure when expressed in a fast-food paradise. Alcoholism wasn’t even possible in the environments where humankind evolved, yet it has plagued the world since the advent of brewer’s yeast. In a preagricultural setting, the evolutionists Randolph Nesse and George Williams speculate in their new book, ““Why We Get Sick,’’ the biological traits that now foster compulsive drinking might have had ““positive effects – for instance, a tendency to [pursue] sources of reward despite difficulties.''
Violent crime, like overeating and drunkenness, has clear biological roots, but that doesn’t mean it’s inherent in anyone’s nature. Males come outfittedfor aggression in many sexually reproducing species, and some human males seem constitutionally more volatile than others. Since the 1970s, numerous studies have linked criminal violence to low levels of the brain chemical serotonin. That association has led some experts, including former National Institute of Mental Health director Frederick Goodwin, to view criminality as a medical disorder that might be predicted through blood testing and prevented through chemical treatment. But the biology of crime isn’t that simple. As social critic Robert Wright noted in a recent New Yorker article, low serotonin may leave people more prone to violence – but poor social conditions seem to lower serotonin levels. Perhaps the best way to counter the biological causes of urban crime, he concludes, is to create better schools and higher-paying jobs – to turn the inner cities into ““places where young men have nonviolent routes to social status.''
The talk of a pharmaceutical war on crime can only feed the suspicions of liberals like Harvard geneticist Richard Lewontin, who warned in 1984 that ““if human social organization . . . is a direct consequence of our biologies, then, except for some gigantic program of genetic engineering, no practice can make a significant alteration of social structure.’’ But there is nothing inherently determinist about a biological perspective – and nothing to be gained by pretending that we live outside of nature. Biology shapes our impulses and aptitudes, but it doesn’t act alone. There is always a context, and always room for resistance. ““It’s biologically implausible to have a gene for something like crime,’’ Sir Michael Rutter, the British child psychiatrist, observed recently. ““It’s like saying there’s a gene for Roman Catholicism.’’ When that precise a gene is found, we’ll have to give up on free will. For now, its status seems safe.
