It's Halloween season, so get ready for a really scary story: The ghost of “Evolutionary Psychology,” which keeps coming back to life, has been re-buried (for the second or third time in the pages of “Scientific American”).
Will it come back to life after this most recent devastating stake through its heart? Only time will tell, but if your blood runs cold at the thought that humans might act like all those scary primates in the darkest jungles, I suggest that you stay inside your house under the blankets with a flashlight and a wreath of garlic, ready to defend yourself.
Why would I joke about something so serious as this headline: “Student Surveys Contradict Claims of Evolved Sex Differences.” My goodness, I have published numerous papers reporting large sex differences, similar to those found in other mammalian species (e.g., Kenrick, Groth, Trost, and Sadalla, 1993; Kenrick, Sadalla, Groth, & Sadalla, 1990; Li & Kenrick, 2006). And now apparently there is real “science” (and American Science at that) to demonstrate that men and women are not evolved, they are instead similar!
To quote the article:
"The science is now getting to a point where there is good data to question some of the assumptions of evolutionary psychology,” says social psychologist Wendy Wood of the University of Southern California.”
The new “science” reported in that article includes a study soon to be published in the journal Sex Roles by Lynn Carol Miller and her colleagues. These researchers asked students how much time and money they invested in short versus long-term mating relationships. They found the proportion was similar for both sexes. Furthermore, both sexes had lower standards for sex partners, and the men in their sample “did not report feeling constrained to have far fewer sexual partners than they truly desired.”
Given that I have published studies showing big sex differences in men’s and women’s standards for sexual partners, why am I laughing at so serious a claim? Well, it’s hard to know where to begin. But I’ll begin by saying that we’ve heard it all before. Findings that men and women are similar get broadcast again and again in places like Science and Scientific American, accompanied each time by claims that evolutionary psychology is now dead, and we can stop worrying about our place in nature. As the article quotes Wendy Wood as saying: “We're the ultimate flexible species.”
Well, do you want to hear something really spooky? Evolutionary psychologists themselves have shown (again and again and again) that men and women are similar in their mate preferences. So it’s easy to demonstrate similarities any time you want to experience deja vu all over again. But alas, we’ve also demonstrated that men and women are sometimes very different in their mate preferences, and in predictable ways. For example, my colleagues and I published a study some 20 years ago showing that when it comes to criteria for long-term mates, men and women are quite similar in their minimum standards (Kenrick et al., 1990). But we found, as many have replicated since, that men lower their standards much more for a one-night stand than women do.
And Norm Li demonstrated in several studies that men and women are quite similar if you ask them to describe an ideal partner (as is typically done in survey studies like the ones that keep getting resurrected to “disprove” evolutionary psychology). If you are a wealthy and charming movie star you get to have your fantasies, but the rest of us need to compromise. Norm used a clever economic methodology in which he brought participants down to earth. He asked participants to allocate a limited budget of mate dollars, so that spending more on one characteristic (like status) meant less left to spend on another (such as physical attractiveness). For participants who had a very high budget (like movie stars) the sex differences were minimized. But for those on a more realistic budget, the sex differences got much larger, right in line with evolutionary predictions.
In the same article, Wendy Wood pushes her sex-roles theory, with startling new findings that women who are more traditional want more traditional men as mates. Again, this is interpreted as showing that evolutionary psychology can be laid to rest (we’re ultimately flexible, after all). On Wood’s view, all the findings of evolutionary psychology can be re-explained by the fact that men are socialized to take on masculine roles (mostly because they are larger and stronger) and females to take on feminine roles (mostly because they bear children and nurse them).
David Buss is quoted in the same article as saying that Wood’s theory is “bizarre” in that it presumes "natural selection has shaped sex differences in male and female bodies, but not in male and female brains and the psychological adaptations those brains contain." As it turns out, most people who have studied gender differences in an evolutionary light share Buss’s reaction to Wood’s theory. That theory simply fails to account for so many findings, including the annoying fact that sex differences found in humans are the same ones found in most other vertebrates, and that those sex differences are linked to hormones like testosterone and estrogen, in humans as they are in other species. For some of my problems with this theory, see my comment on Wood and Eagly’s theory titled: “The Darwin is in the details,” or my 2006 essay: “Evolutionary psychology: Resistance is futile.” For an earlier reaction to attacks similar to the latest death declaration, see my 1995 essay “Evolutionary psychology versus the confederacy of dunces” (and please accept my apologies for still not taking seriously criticisms that were answered decades ago).
Yes, humans are not typical mammals in some ways – human males devote many more resources to their offspring than do most other mammals. But evolutionary psychologists aren’t shocked by this, sex similarities are found in other species, and when they are found, they are associated with correspondent predictable variations in sex roles, mate selection, and morphology. Understanding variations in sexual selection and parental investment helps us understand why human females also compete for mates, and why human males are not twice as large as females (as they often are in species like elephant seals, where males only invest in mating effort). In other species such as phalaropes, the males devote more care to offspring than do the females, and guess what, the females are more competitive and more colorful than the males, just as you’d expect from sexual selection theory.
And yes, humans are flexible. But again, we’re not unique in this regard. Other species, such as indigo buntings, alternate between monogamous and polygynous mating depending on ecological factors (just as humans do). See my earlier post on evolution and flexibility (The Mind as a Coloring Book)
David Buss has a longer response you can see if you click here. I also cite some thoughtful empirical papers below by Buss and his colleagues David Schmitt. But there’s a lot more to say about why Buss, like the rest of us who study human behavior in evolutionary light, doesn’t take this latest round of “science” seriously. Before you believe the next report that evolutionary psychology has been laid to rest by findings of sex similarities or behavioral flexibility, check out David Geary’s very thoughtful work on this subject (cited below). If you find logical arguments scary, though, I should warn you, Geary may keep you up at night.
Click below to read the next round (in which Eagly and Wood "respond"):
Buss, D., & Schmitt, D. (1993). Sexual strategies theory: An evolutionary perspective on human mating. Psychological Review, 100, 204-232.
Geary, D.C. (1998). Male, Female: The evolution of human sex differences. Washington, DC: APA Publications.
Geary, D. C. (2000). Evolution and the proximate expression of human paternal investment. Psychological Bulletin, 126, 55-77.
Kenrick, D.T. (1995). Evolutionary theory versus the confederacy of dunces. Psychological Inquiry, 6, 56-61.
Kenrick, D.T. (2006). Evolutionary psychology: Resistance is futile. Psychological Inquiry, 17, 102-108.
Kenrick, D.T., Groth, G.R., Trost, M.R., and Sadalla, E.K. (1993). Integrating evolutionary and social exchange perspectives on relationships: Effects of gender, self-appraisal, and involvement level on mate selection criteria. Journal of Personality and Social Psychology, 64, 951-969.
Kenrick, D.T., Sadalla, E.K., Groth, G., & Trost, M.R. (1990). Evolution, traits, and the stages of human courtship: Qualifying the parental investment model. Journal of Personality, 58, 97-116.
Kenrick, D.T., & Li. N. (2000). The Darwin is in the details. American Psychologist, 55, 1060-1061.
Li, N.P., & Kenrick, D.T. (2006). Sex similarities and differences in preferences for short-term mates: What, whether, and why. Journal of Personality and Social Psychology, 90, 468-489.
Li, N.P., Bailey, J. M., Kenrick, D.T., & Linsenmeier, J.A. (2002). The necessities and luxuries of mate preferences: Testing the trade-offs. Journal of Personality and Social Psychology, 82, 947-955.
Minkel, J.R. (2010). Student surveys contradict claims of evolved sex differences. Scientific American, October 14.
Schmitt, D.P. (2003). Universal sex differences in the desire for sexual variety: Tests from 52 nations, 6 continents, and 13 islands. Journal of Personality & Social Psychology, 85, 85-104.
Schmitt, D.P. (2006). Sociosexuality from Argentina to Zimbabwe: A 48-nation study of sex, culture, and strategies of human mating. Behavioral & Brain Sciences, 28, 247–311.