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Stanford Report, September 20, 2000

Paul Ehrlich challenges evolutionary psychology and the 'selfish gene' in his new book, Human Natures


Do "selfish genes" program men to be more promiscuous than women?

Beneath the veneer of civility, are people innately aggressive?

Some researchers -- and a growing segment of the general population -- would answer "yes" to those and a host of other questions, suggesting that we are tightly programmed by our genes.

But according to Stanford evolutionist Paul R. Ehrlich, there is little scientific basis for such widely accepted notions.

Ehrlich challenges the so-called "selfish gene" and other tenets of evolutionary psychology in his wide-ranging new book, Human Natures: Genes, Cultures and the Human Prospect (Shearwater Books/Island Press, Washington, D.C.).

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photo: L.A. Cicero

In this well-documented book, Ehrlich discusses a number of controversial issues: why people evolved an upright posture; what happened to the Neanderthals; how our brains work; how language evolved; what led to the very sudden appearance of modern human beings; why race is an outdated concept; how can we account for altruism and aggression; why humans enjoy sex all year round; why women have orgasms; why many of us crave hot fudge sundaes; how religion and states evolved; and the origin of ethics.

Ehrlich, author of The Population Bomb and many other books and scientific articles, is Bing Professor of Population Studies and president of the Center for Conservation Biology at Stanford.

In Human Natures, he expresses concern about the growing resurgence of genetic determinism -- the belief that human DNA contains "instructions" that dictate behavior, including so-called "genes for rape," "gay genes," "criminal genes" and "genes for intelligence."

"There is an unhappy predilection, especially in the United States, not only to overrate the effect of genetic evolution but also to underrate the effect of cultural evolution," writes Ehrlich.

"Uniquely in our species, changes in culture have been fully as important in producing our natures as have changes in the hereditary information passed on by our ancestors," he adds.

Take, for example, the popular belief that human males are genetically wired to be more promiscuous than females.

"Women, like men, evolved to be smart," says Ehrlich, "and they certainly don't need to be rocket scientists to understand that they make a bigger potential commitment to each sex act than do men. That alone, rather than an evolved tendency in men to reproduce more, could explain differences in attitudes toward fidelity."

And on the question of whether human beings are innately aggressive, Ehrlich points out that we are "at least as often peaceful and resolve conflicts nonviolently. Maybe we should talk about us as being the 'conciliatory apes.'"

He dismisses the notion of the "selfish gene" --- the idea that genes are simply tiny, self-reproducing units with goals of their own.

"Much of the problem," according to Ehrlich, "traces to the field of evolutionary psychology, where knowledge of genetics and evolution tends to trail far behind the knowledge of psychology. Indeed, talk about genes being 'self-replicating' or 'selfish' is very misleading. Genes cannot be reproduced except by being imbedded in a complex cellular mechanism -- they're about as self-replicating as a printed page lying in a copying machine.

"Furthermore," he maintains, "it is critical that genes act in concert and not interfere with the functioning of other genes. Thus if one is silly enough to assign human-like motivation to them, it would be as sensible to describe them as 'cooperative' as to call them 'selfish.'

"The influences of an animal's genes depend upon the environment in which it lives, and there can be no environments without genes, since for the physical world to be an 'environment' there must be organisms, and all organisms modify their environments," he adds.

"Genes and environments are fundamentally connected," notes Ehrlich, "and they interact in complex ways -- something we must always keep in mind when we necessarily, but artificially, separate them for purposes of analysis and discussion."

Ehrlich contends that the long-standing debate over "nature vs. nurture" is largely a false dichotomy.

"Especially unfortunate," he says, "is the common view of the public that if something is 'genetic' it can't be altered. Even the behavioral effects of Down syndrome, traceable to a major genetic defect -- the presence of an extra chromosome -- can be greatly influenced by providing an affected child with a stimulating environment."

Human Natures emphasizes that, while genetic evolution clearly has influenced human behavior, a much more important factor is cultural evolution -- "changes in the vast body of non-genetic evolution that humanity stores in its brains, books, buildings, computers, films and the like."

From a biological perspective, Ehrlich points out, the human genome does not have remotely enough genes to program the connections in our brain that control behavior.

"There are on the order of one billion connections for every gene," he argues. "Our 'gene shortage' is one reason human infants and young children are so helpless. Their helplessness allows the physical and cultural environments to do the brain programming that our hereditary endowment couldn't manage. It's that environmental input that gives us the adaptability that is the hallmark of humanity. We could never have evolved as genetically controlled robots."

Ehrlich, known for his advocacy of conservation, concludes Human Natures with a discussion on the evolution of environmental ethics and other human values.

"A modern knowledge of biological and cultural evolution helps us grasp what kinds of animals we are, where we came from and how we fit into the natural world," he writes.

Ehrlich is convinced that many scientists know already the directions in which solutions to the population-environment crisis lie.

"Gradual and humane reduction of the size of the human population, limiting of wasteful per capita consumption among the rich to allow room for increased consumption by the poor, use of more environmentally benign technologies and increased equity among and within nations will all be required.

"That's what we need to do, and interdisciplinary teams of scientists are even starting to figure out how we might do it. For instance, it's clear that individual economic incentives must be brought into alignment with society's long-term best interests."

But pursuing the "how" goal will require much more effort, Ehrlich claims.

"Our cultural evolution on the technological front, our ability to do, has vastly outpaced cultural evolution in knowledge of the environment and human relations, our ability to understand," he concludes. "To change our ways we must know ourselves, including our history. I hope Human Natures will be a contribution to building that understanding."

Ehrlich joined the department of biological sciences at Stanford in 1959. In the early 1960s he developed the theory of coevolution with then Stanford faculty member Peter Raven. Their work began one of the most active and important areas of evolutionary-ecological theory.


He also is recipient of the Sierra Club's John Muir Award, the World Wildlife Fund's Gold Medal Award, a MacArthur Prize Fellowship, the Crafoord Prize of the Royal Swedish Academy of Sciences (given in lieu of a Nobel Prize in areas where the Nobel is not given) and the United Nations' Sasakawa Environment Prize. SR