Stanford Report Online

Stanford Report, April 4, 2001
Genes don't control behavior, Ehrlich says, urging studies of cultural evolution


"Evolutionary psychology" -- the discipline that attempts to explain much of human behavior as a creation of natural selection that operated during our hunter-gatherer past -- "is dead but doesn't seem to know it yet," evolutionist Paul R. Ehrlich told the annual meeting of the American Institute of Biological Sciences (AIBS) in Arlington, Va., on March 26.

Paul Ehrlich.
photo: L.A. Cicero

"Genetic evolution did not determine most of how we act or provide us all with a pre-programmed 'human nature,'" he added. "For instance, there is no reason to believe that human beings are either innately violent or innately peaceful, instinctively disposed to wreck their environments or to be conservationists, or born genetically gay or genetically straight."

Ehrlich, the Bing Professor of Population Studies at Stanford, president of the Center for Conservation Biology and a past president of the AIBS, said the Human Genome Project had "put the final nail in the coffin of genetic determinism by showing that human beings have only some 26,000 to 38,000 genes -- many of which are closely similar or identical to those of much simpler animals like fruit flies." This, he claimed, made the problem of "gene shortage" even more serious for the views of evolutionary psychologists than it was when it was thought that there probably were 100,000 genes or more.

"The complexities of human behavior must be coded into hundreds of trillions of often-changing connections among perhaps a trillion chemically varying nerve cells in the brain. Even if every one of our roughly 30,000 genes were dedicated to wiring our brains, each would need to control the hooking up of about a billion connections," Ehrlich explained.

"But genes must also contribute to the assembly of all our other complex organs. Even if we had a million genes that could be dedicated to our brains, they couldn't begin to determine how those nerve cells interact," he stated. "Our genes have more than enough to do just making us extraordinarily smart, giving us the physical talents required for speech and tool making, and influencing a few key behavioral features such as our interest in sex and our penchant for keeping track of who's related to whom."

Human Natures

Ehrlich first wrote about "gene shortage" in his recent book Human Natures: Genes, Cultures, and the Human Prospect. In addition to gene shortage, he pointed out several other indicators showing that culture, not genes, controls the vast majority of our interesting behavior.

"Children born into one culture and transferred as infants into another invariably acquire the language and customs of the adoptive culture. Identical twins, with identical genes, invariably show many behavioral differences. And people have practiced contraception for thousands of years even though if genes were running the show, they would never permit it," he argued.

Ehrlich pointed out that the brain "is the only organ in the body that requires enormous input of information from the environment, including especially the cultural environment, in order to develop properly. And the amount of non-genetic information (culture) to which people are exposed is vastly greater than the store of genetic information in the human genome. Indeed a single cultural artifact, a Boeing 747, has orders of magnitude more parts than the human genome has genes.

"It's high time for some science writers to stop feeding nonsensical 'pop' behavioral evolution to the American public, and to explain what geneticists have long known," Ehrlich continued. "Postulating an imaginary 'human nature' -- an evolved set of genetically determined proclivities -- is not going to help us solve critical problems such as environmental deterioration and violence. If we want to understand human behavior we must understand the roles of culture and chance in its genesis.

"We know that culture evolves," he added. "Widespread caring for people of different cultures in far-off lands and strong, broadly based concern for the environment are recent cultural adaptations. And if we want to change further the way human beings behave toward each other and their life-support systems, the Human Genome Project has made it crystal clear that learning to steer cultural evolution is basically the only option available."


In his AIBS speech, Ehrlich challenged his fellow biologists to collaborate with social scientists to develop a more thorough understanding of how culture evolves.

"We comprehend something about the spread of ideas, but almost nothing about their generation," he asserted. "We know that ethics evolve, but know little about how to make them evolve more rapidly. Interestingly, the business community is providing some clues through the relatively new science of marketing. Scientists should not ignore the findings of marketing simply because they may disapprove of some of the uses the business community puts them to."

According to Ehrlich, "We must strive to evolve a new ethic that would have almost everyone put preserving humanity's vital store of natural capital -- the microorganisms, plants and other animals of Earth -- near the top of their ethical priorities. Scientists need to direct that evolution by 'marketing' such a set of ethics, doing the necessary market research, selecting appropriate goals, creating appropriate images and emotional associations, and carefully monitoring the performance of the 'product.'"

If our marketing campaign fails, he warned, we are unlikely to be able to maintain the flow of ecosystem services upon which society depends.

"It is highly unlikely that human beings will ever create a utopia," Ehrlich concluded, "but by working harder to consciously influence cultural evolution we could do a lot better than we're doing today."