You must turn off your ad blocker to use Psych Web; however, we are taking pains to keep advertising minimal and unobtrusive (one ad at the top of each page) so interference to your reading should be minimal.

If you need instructions for turning off common ad-blocking programs, click here.

If you already know how to turn off your ad blocker, just hit the refresh icon or F5 after you do it, to see the page.

Psi man mascot

Evolutionary Psychology

Students of animal behavior have been applying concepts from ethology to human behavior for decades. Tinbergen and Lorenz suggested many ways in which their concepts applied to humans.

The ideas of classic ethology were popularized by authors like Tinbergen's student Desmond Morris. He wrote a bestseller in 1967 called The Naked Ape. It was full of speculations about how human behavior evolved.

Lorenz's student Iraneous Eibl-Eibes­feldt made human ethology his special­ty. He applied the naturalistic observa­tional techniques of ethology to humans.

Eibl-Eibesfeldt recorded behavior of people in native cultures in their tribal setting with the side-viewing technique described in Chapter 1. Eibl-Eibesfeldt wrote a textbook called Human Ethology (1989) introducing ethological concepts and showing how they applied to humans.

The phrase evolutionary psychology started to become poopular around 1990. Like sociobiology and human ethology, this discipline interprets human behavior as a product of evolution.

Evolutionary psychologists examine how human traits affect differential survival and reproduction, which is always the mechanism of evolution. Topics can include anything but tend to emphasize classic ethological themes, such as:

1. Factors influencing mate selection

Researchers have found that people generally find statistically average faces more attractive than faces with extreme features. Humans (and animals) prefer symmetry of the body and face in a potential mate. People value healthy skin and consider it more attractive than blemished or diseased skin.

2. Nonverbal and largely automatic forms of social communication

Humans use species-typical displays. Eibl-Eibesfeldt studied the eyebrow flash (briefly raised eye­brows) that serves as a greeting display in humans (but do not do it in Japan, where it is considered crude and sexual).

Eibl-Eibesfeldt verified an observation made by Margaret Mead, the anthropol­ogist: young girls all over the world use a stereotyped flirtation display (a glance, followed by looking away, covering the face, giggling, and looking back).

David R. Buss and research associates at the University of Texas studied uncon­scious social signalling among dating-age adults. He identified signals such as the neck cant (a sexy tilt of the head, common in females) and fiddling with hair (common when a person wants to impress somebody of the opposite sex). Many of Buss's observations were made unobtrusively at places like bars where young single people assess each other.

3. Adaptive function of things we take for granted

What is the adaptive function of a yawn? For primates, it is a domi­nance display. However, it also cools the brain.

Competing explanations sometimes lead to competing predictions that can be tested with research. Beha­viors can have multiple functions, so there can be more than one evol­utionary explanation for a trait.

4. Evolutionary explanations of strange or repugnant events

Honor killings and jealous rages by spurned males may have functioned to enhance reproductive success in the ancestral environment. Women who stay with an abuser may be acting out an ancient script that was once genetically advantageous. The Stockholm Syndrome (in which kidnapped people bond with their captors) may have been an adaptive response in ancient times.


In 1975, a Harvard biologist who special­ized in the study of ants, Edward O. Wilson, proposed a new discipline to be called sociobiology. It would focus on the biological and evolutionary underpinnings of social behavior.

Wilson wrote a book titled Sociobiology: The New Synthesis (1975) in which he proposed genetic explanations of many human social behaviors. Wilson's book, and his proposed field of study, was immediately attacked by social scien­tists, including psychologists.

Critics like anthropologist Sherry L. Washburn (1978) argued that Wilson's ideas were oversimplified and danger­ous. Washburn wrote:

Postulating genes to account for behaviors is a major feature of the application of sociobiology to the interpretation of human behaviors. For example, in the last chapter of Sociobiology (Wilson, 1975), genes are postulated to account for more than 25 behavioral situations. There are conformer genes, genes for flexibility, genes predisposing to cultural differences...

... The logic [used by sociologists] is that there must be altruistic genes to account for altruistic acts–just as we learned many years ago that if there are criminal acts there must be criminal genes.

Washburn was alluding to the dark days of eugenics, a pre-WW II theory that was embraced by the Nazis and used to justify the extermination of "undesirable elements" such as criminals, Jews, homosexuals, and mentally retarded people. This was rationalized by declaring they were genetically inferior.

What was Washburn's objection to sociobiology?

Eugenics first proposed in the 1880s by Sir Francis Galton and was a straight­forward but simple-minded extrapola­tion of Darwinian "survival of the fittest" ideas to the human race. Lack of fitness was equated with criminality, deviance from social norms, and race mixing.

For a time, eugenics was endorsed at the highest levels of the British and U.S. governments. People like Winston Churchill in Britain and President Calvin Coolidge of the U.S. endorsed it.

The federal Immigration Act of 1924, in the U.S., was promoted by Eugenics Research Association president Albert Johnson. It established an immigrant quota system to limit the amount of supposedly inferior genes from entering the country. Shortly after that, eugenics fell into disrepute.

What was eugenics and how did it relate to objections against sociobiology?

Related issues still arouse passion. In 2007, the Surgeon General of the United States recommended that all pregnant women receive a simple new test for Down Syndrome.

Parents of children with Down Syndrome, as well as adults with Down Syndrome, immediately protested that this was a proposal for genocide. Many women would elect to terminate a pregnancy if a fetus tested positive for Down Syndrome.

Members of online discussion groups for autism and Asperger's Syndrome have similar reactions to proposals for genetic detection of autism. The possibility of identifying a gene for congenital deaf­ness raises similar fears in the deaf community. Issues like this will not go away soon, because genetic testing will become cheaper and more precise in the future.

Ullica Segerstrale (2000) chronicled the "science wars" over socio­biology. She started as a critic of sociobiology in the 1970s, taking the side of many prominent scientists such as Washburn.

Segerstrale did a doctoral thesis on the sociobiology controversy and continued to follow it for decades, attending scien­tific meetings and reading journal articles. After twenty-five years, Seger­strale concluded that, contrary to her expectations, the sociobiological perspective had "won."

What did Segerstrale conclude after 25 years?

Sociobiology had stimulated the form­ation of pro­fessional societies and journals reporting thousands of research programs. Its premises about the evolutionary roots of social behavior in humans were becoming widely accepted on the basis of sound research.

In retrospect, a major problem with Wilson's presentation of sociobiology was his tendency to refer in a shorthand way to "the gene" for a very specific trait or behavior. Not only Wilson but the whole field of genetics suffered from oversimplified public presentations of genetic research. Caruso (2007) wrote:

Over the last two decades, for example, there has been a steady stream of news about researchers discovering "the gene" that links people to diabetes, Alzheimer's, obesity, schizophrenia, depression and many other afflictions.

Yet most of those gene-disease links–as many as 95 percent of them, according to one British study published in 2003– don't hold up to closer scrutiny. Instead, follow-up studies find that, if there is any measurable genetic link to these common diseases, it results from complex interactions of many genes with one another, as well as with the environment (Caruso, 2007).

Note that Caruso does not say 95% of the gene-disease links are false. Rather, genetic influences turn out to be more complex than implied by headlines. News reports make it sound like a few base pairs on a stretch of DNA can cause behaviors to happen. Genetic influences are seldom that direct.

Wilson's book, back in 1975, suffered from the same problem as news headlines about genetic discoveries in the 21st Century. Shorthand descriptions like "a gene for..." are generally misleading, because genetic interactions are complex.

However, evolution does have an impact on the brain and behavior, including social behavior. The evolutionary perspective on social behavior is not invalid or false, it is just more complex than typical headlines or claims about genes. The field of evolutionary psych­ology is thriving.

The label "sociobiology," on the other hand, became unpopular. In 1997 the journal Ethology and Sociobiology changed its name to Evolution and Human Behavior. Edward O. Wilson accused them of intellectual cowardice.

Wilson himself remained influential among psychologists. In 1999 he was the keynote speaker at the American Psychological Association convention a few months before New Years Day 2000. The convention addressed future trends.

Wilson did not talk specifically about sociobiology at that gathering. He discussed his book Consilience: The Unity of Knowledge (1998), which urged the integration of all natural sciences, including biology, ethology, and psych­ology.


Caruso, D. (2007, February 18) Genetic tests offer promise, but raise questions, too. New York Times. Retrieved from:

Segerstrale, U. (2000) Defenders of the Truth: The Sociobiology Debate. Oxford, England: Oxford University Press.

Washburn, S. (1978, November). What we can't learn about people from apes. Human Nature, pp.70-75.

Wilson, E. O. (1998) Consilience: The Unity of Knowledge. Boston, MA: Little, Brown.

Wilson, E. O. (1975) Sociobiology: The New Synthesis. Cambridge, MA: The Belknap Press of Harvard University Press.

Write to Dr. Dewey at

Don't see what you need? Psych Web has over 1,000 pages, so it may be elsewhere on the site. Do a site-specific Google search using the box below.