Human Natures: Genes, Cultures, and the Human Prospect
by Paul R. Ehrlich
Island. 531 pp. $29.95

Paul R. Ehrlich, the Stanford University biologist and environmental activist, is perhaps best known for a prediction he offered in his 1968 book, The Population Bomb: namely, that by the 1980’s the world would be in the throes of resource scarcity severe enough to produce riots and widespread famine. This forecast became the basis of a famous public wager with the late economist Julian Simon that Ehrlich lost hands down.

Given this track record, I had little hope, prior to opening it, that Ehrlich’s new book would prove more solid. Unfortunately, my doubts were justified: Human Natures is a highly polemical attempt to deny the existence of certain core characteristics and behaviors that constitute a single “human nature.” The attempt fails.

The concept of human nature, as old as the Greeks, has been intensely politicized over the past 200 years. To many people on the Left, the very idea of such a single human nature came to seem little more than a camouflage for efforts to limit human possibilities and human freedom. By the middle of the 20th century, most social scientists had become committed to the contrary idea that human behavior was, in Emile Durkheim’s phrase, “socially constructed,” that is, dependent not on any biological givens but on the process of socialization. Since, moreover, human societies are almost limitless in their variety and plasticity, it follows that there are no universal standards by which one can make value judgments about different individuals or cultures. This last view is still propounded in countless “cultural studies” programs in universities around the country.

But, in one of the truly arresting shifts of intellectual history over the past five decades, the concept of human nature has undergone a remarkable resuscitation. This development has mainly occurred not in the social sciences but in the life sciences, and its sources are diverse. From evolutionary biology has come the notion that the brain is not a tabula rasa to be shaped by society but rather an organ that has adapted over time to deal with its environment and to solve certain key problems of social competition and cooperation. From behavioral genetics have come rigorous statistical methods for teasing out the genetic from the environmental components of behavior. From cognitive neuroscience have come discoveries linking behavior to the physiology and biochemistry of the brain. And then there is molecular biology, whose decoding of the human genome has begun to open up the actual digital code governing biological development.



Paul Ehrlich’s book is a reaction to these new findings. It puts forward two arguments against the existence of a single “human nature,” one somewhat sophisticated and one somewhat silly.

The sophisticated argument, articulated over the years by the Harvard geneticist Richard Lewontin, holds that, because of the complex interactions between genes and environment, a given organism’s genotype (i.e., its DNA) never fully determines its phenotype, the actual living creature that eventually develops. For an obvious example, consider what happens in utero: if a pregnant mother is malnourished, drinks excessively, or consumes drugs, the same genes will produce a child physically and mentally different from the one that would have been born if she had taken better care of herself.

This line of reasoning is unexceptionable, but it hardly settles anything. Many phenotypical possibilities are, in fact, distributed normally in the general population—if plotted on a chart, they would form a bell curve. It is true that, say, the average height of a population depends on diet, among other things, but there is still a range of identifiably normal heights, and there are dwarves and giants who can fairly be described in statistical terms as abnormal. It is also true that, in some cases, a relatively simple linear relationship obtains between environment and phenotype; the better the mother’s prenatal diet, the healthier the subsequent child. Once again, however, these sorts of variance no more disprove the existence of a species-typical “nature” than they suggest that being born stunted is as desirable as being born healthy.

Ehrlich’s second argument, the silly one, takes aim at a straw man. Obviously annoyed at the tendency of the popular press to speak about genes that “code for” everything from fatness to intelligence to aggression, he stresses repeatedly that human beings are, at their core, cultural animals, and that their behavior is heavily influenced by what they learn from both the natural and the social environment. There is a simpleminded point that Ehrlich is aiming at in asserting multiple “human natures” (to cite the title of his book): that peoples differ culturally from one another, and also that cultures change over time. Thus, at one juncture he notes that “citizens of long-standing democracies have different human natures from those accustomed to living under dictatorships,” while at another he observes that “the natures of many Japanese people changed greatly in response to the defeat and the revelation of Japanese war crimes.”

All this reminds one of the memorably sweeping phrase uttered by a character in one of Virginia Woolf’s novels: “on or about December, 1910, human character changed.” Admittedly, there has been a tendency on the part of the press and some popular science writers to hype the importance of genetics and to draw dubious links between complex higher-level behaviors and simple genetic causes. But the scientists who have sought to reestablish the legitimacy of the idea of human nature are fully aware that human beings are cultural animals, and that genes and environment interact in a complex manner. Genetics, in their view, does not produce deterministic drives or instincts but rather capabilities for cultural learning whose content is filled in after birth. The acquisition of language is perhaps the clearest example of this process.

Still, what the new biology does argue is that there are species-typical ways in which we humans learn, and there are also limits to what we can learn that ultimately restrict the adaptability of human behavior. Ehrlich himself provides many examples of this in his book, even as his fastidious sense of political correctness prevents him from seeing the implications of what he is saying.

Take sexual behavior—which, as Ehrlich points out, has a strong genetic component: men and women have different chromosomes and brain structures, and they also behave differently when it comes to selecting sexual partners. (According to evolutionary psychologists, that difference is traceable to their differing degrees of investment in offspring.) Although we know of no biochemical route linking the male chromosomes to promiscuity, a tremendous amount of circumstantial evidence suggests that there is such a link, including the fact there are virtually no cultures where male promiscuity is not discernible. Indeed, in our own society, 30 years after the feminist revolution, men still remain greater consumers of pornography and frequenters of prostitutes than women, and homosexual men are far more promiscuous than homosexual women. Yet after plowing through these and other facts, Ehrlich waffles for several pages before finally pronouncing the genetic evidence unproven.

Ehrlich is similarly intent on denying that there is anything innate about the human, and particularly the male, proclivity for violence, aggression, or hierarchy. Yet once again he is disputed by the data that he himself cites, including research by Frans de Waal and Richard Wrangham documenting group warfare among chimpanzees (who share a common descent with human beings from a chimp-like ancestor), or Lawrence Keeley’s comprehensive survey of archaeological evidence showing that hunter-gatherer societies engage not only in warfare but in genocide. In short, Ehrlich does not merely commit the sin of selecting only the evidence that will support his conclusions; he arrives at his conclusions in the face of his own evidence.



If the bet Ehrlich lost to Julian Simon has evidently not taught him to be cautious, he is particularly thoughtless, in a manner characteristic of many scientists, on a question central to his book: whether human nature can tell us anything relevant about human values. His answer to that question is a blunt “no.”

As a man of the Left, Ehrlich is committed to universal human equality and equal respect for the world’s diverse peoples. But on what grounds is this commitment based? If the “human nature” of the Japanese changed—from genocidal militarists before World War II to cooperative pacifists after it—are both Japanese “natures” entitled to equal respect? Was the U.S. wrong to wage war on the former but not on the latter? Or, again, if human natures are indeed as diverse as Ehrlich claims, why should we refrain from looking down upon peoples who as a group are less intelligent or less well organized or crueler than we are?

The answer, of course, lies in the fact that we all share a common humanity that consists of something more than our crude physical natures. For Christians as for Jews, human dignity lies in our having been created in the image of God. For a nonreligious person like (one assumes) Ehrlich, the only possible source of shared human dignity must lie in the existence not of multiple “human natures” but of a common, and single, and distinctively human nature. Although he fails to recognize it, the entire moral and political universe in which he operates depends on this proposition.

At the end of his book, Ehrlich expresses the hope that people will some day stop talking about the concept of human nature. But, thanks to developments in contemporary biology, this concept is on its way back. If he is ready to wager on whether we will still be taking it seriously in a decade or two, I would gladly accept the challenge.



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