David Buss defends evolved sex differences (exclusive!)

October 15, 2010

This week Scientific American ran an article of mine, “Student Surveys Contradict Claims of Evolved Sex Differences.” Here’s the gist:

For more than three decades evolutionary psychologists have advanced a simple theory of human sexuality: because men invest less reproductive effort in sperm than women do in eggs, men’s and women’s brains have been shaped differently by evolution. As a result, men are eager for sex whereas women are relatively choosy. But a steady stream of recent evidence suggests this paradigm could be in need of a makeover.

A highly cited 1993 paper on evolved sex differences (linked to below) served as the story’s jumping off point and foil. Evolutionary psychologist David Buss of the University of Texas at Austin, a co-author of that paper, kindly responded to a query of mine while I was writing the story, laying out his objections to the evidence I cited in the article. I knew I wasn’t going to have room to do justice to his views, so I asked him if I could post his comments to this blog. He did me one better: he wrote a direct response to my article, which I’m reprinting below in its entirety. Naturally, this will make more sense after you’ve read my article. :)

Evolved Sex Differences: Not Gone, Not Forgotten, and Not Explained by Alternative Hypotheses

It is both astonishing and disturbing that evolutionary psychology as a field, and the specific hypotheses that have been advanced under its broad umbrella, continue to be so badly mischaracterized by other “scientists” as well as by science journalists writing for popular media (see, for example, Dr. Kurzban’s recent account of one vivid example directly related to the current article). That these errors and scholarly lapses continue to occur, despite numerous attempts to correct common misunderstandings about them, suggests poor scholarship, non-scientific motivations of the ideological or religious kind, or both.

Given the large number of lapses contained in the current article and in thecomments of the authors it quotes, I’ll restrict my comments to a few of the more egregious errors and point interested readers to the relevant scientific sources so they canjudge for themselves.

The first problem is that sexual strategies theory, initially advanced in 1993, is erroneously depicted. Contrary to the cartoonish depiction of “eager males-choosy females,” our theory proposed that BOTH men AND women have evolved short-term AND long-term sexual strategies. Subsequent publications from my own lab and the labs of other scientists (e.g., Gangestad, S.W., & Thornhill, R. (2008). Human oestrus. Proceedings of the Royal Society B, 275, 991-1000) have tested specific evolutionary hypotheses about the benefits to women of short-term mating strategies. Although the final word is not in, currently viable hypotheses for women’s short-term sexual strategies include increased access to resources, securing good genes, and trading up to a better mating partner. Readers in the science of female sexuality should check out my recent book, co-authored with Dr. Cindy Meston, entitled Why Women Have Sex.

Just as some women pursue a short-term sexual strategy some of the time, many men pursue a long-term mating strategy marked by love, commitment, and heavy parental investment in children. Humans have a complex “menu” of mating strategies, selectively deployed depending on predictable contexts such as population density, matevalue, and sex ratio. Given that these elements have been central to sexual strategiestheory since its inception 17 years ago, responsible scientists and science journalists should put a stop to the cartoonish depiction of sexual strategies theory.

Now let’s address the issue of whether men and women differ in their psychology of short-term mating. Among the 9 key hypotheses and 22 empirical predictions contained in the original version of sexual strategies theory is indeed the hypothesis that men will attach a higher motivational priority to short-term mating, depending on contextual factors such as personal mate value, sex ratio in the mating pool, risk, and cost. The logic follows from Trivers’s theory of parental investment and sexual selection, which has been abundantly supported in the non-human and human scientific literatures. Indeed, the scientific evidence supporting this prediction for humans is overwhelming. Contra the data cited in the current article, readers should consult the massive cross-cultural studies that have been conducted both by evolutionary psychologists such as David Schmitt and by scientists who have no commitments to evolutionary psychology, such as Dr. Richard Lippa. The Lippa study, for example, tested more than 200,000 individuals across 53 different nations and found robust sex differences precisely as predicted by sexual strategies theory, as well as findings flatly contradicting the Eagly-Wood “alternative” theory [that women and men are simply responding to their society’s division of labor]. I urge readers who really doubt the existence of sex differences on variables such as desire for sexual variety to consult these massive cross-cultural studies. Indeed, these psychological sex differences are among the largest psychological sex differences ever discovered, as meta-analyses by Dr. Janet Hyde of the University of Wisconsin have documented.

Although some researchers try to market their data as contradicting hypotheses about evolved sex differences, viewed in the broader context of the massive data sets such as those of Janet Hyde, Richard Lippa, and David Schmitt, dispassionate readers will come to the conclusion that massive weight of the scientific evidence supports thefundamental tenets of sexual strategies theory.

David M. Buss, Ph.D.

Professor of Psychology

Head, IDEP Area

For those who want to know how Eagly and Wood’s alternative paradigm might account for the cross-cultural data collected by Schmitt and Lippa, here’s your starting point. Happy reading!

Update [10/18/10]: There’s a great exchange in the comments section of my story between Buss’s co-author David Schmitt (comments 20 and 21) and a commenter who goes by “figleaf” (comment 25).

Here are the choice bits, first from Schmitt:

This article contains mischaracterizations of current evolutionary psychological thinking on sex differences in sexuality.

First, Sexual Strategies Theory (Buss & Schmitt, 1993) did not claim that all men are easy short-term maters and all women are choosy long-term maters. To the contrary, the key contribution of Sexual Strategies Theory to psychological science was to highlight the differences within men when pursuing short-term mates versus long-term mates and within women when pursuing short-term mates versus long-term mates. Subsequent to this development within evolutionary psychology, several additional theories (e.g., Strategic Pluralism Theory, Life History Theory, Attachment Theory) have been elaborated and extended to accommodate this important advance in adaptationist thinking. Current evolutionary thinking continues to focus on the mating psychology differences within men and within women, as well as highlighting fundamental differences between the genders. It seems only ill-informed researchers who have failed to read the massive literature in the area and the ideologically-driven critics of evolutionary psychology continue to depict the easy men versus choosy women straw man. This does nothing but hurt psychological science.

And from figleaf’s response:

@Davidschmidt #20: I’m gratified to hear that actual lower-case evolutionary psychologists have more nuanced theory than… 99% of all popular accounts thereof let on.

But if that’s true then Miller’s work should hardly be threatening at all: her work seems only to threaten established perceptions routinely promoted by ideology-driven *adherents* of the one-dimensional promiscuous-men/particular-women model articulated ad nauseum in the popular press.

Indeed, if as you say non-pop professional EP is confined by adherence to a single straw-mannish model of sexual selection then by putting pressure on that model Miller ought to be giving real EPs an opportunity to present the more subtle, more sophisticated, and more accurate Sexual Strategies Theory you’re endorsing.

Because, seriously Dude, out here in the real world we’re not hearing a lot about those, m’kay? Now’s your chance. Why waste it attacking that line of research when you could instead co-opt it as confirming your more sophisticated readings against the distortions introduced by ill-informed but highly-enthusiastic ideologues who keep misappropriating the work real EPs?

Because it’s not like progressives have a monopoly on “political correctness.” And in the case of EP it’s the ideological adherents who seem to be doing more damage to the actual work than are its equally ideological antagonists.

Now that’s discourse.

7 Responses to “David Buss defends evolved sex differences (exclusive!)”

  1. Very interesting, thanks for posting this. A lot of theory, not to mention a huge amount of popular mythos, revolves around the plausibility and eventual fate of the EP theories of how sex differences are manifested in humans. In spite of this, good interactive discussions have been relatively rare. Buller’s book is the only one I’ve seen that comes close to a reasonable critique. It’s good to see someone else taking on Buss no specifics in a fair manner. In generally, I find that EP proposals tend to be either accepted or rejected far too casually without reference to evidence.

  2. […] David Buss defends evolved sex differences (exclusive!) […]

  3. NonBreeder Says:

    This is just regular sexism dressed up as evolution. A huge data set of women displaying socialized behaviour does nothing to sway me in the direction of EP. It’s simple social pressure, not biology.

    • Breeder Says:

      If it’s social pressure, then where did that social pressure come from?

      It’s about time ‘social’, ‘cultural’ and ‘developmental’ models are stopped being used loosely because they are intellectual cop outs.

      Rejecting the biological precedent is going to lead to a social sciences model that has no fundamental basis to begin from.

  4. Phil K Says:

    It seems that this topic seems to elicit strong [evolved] emotional responses, but regardless of where you sit on the Evolutionary Psychology debate, there is no room for ideology and emotions in the debate.

    I trust in the scientific process and I have to say the weight of evidence in support of EP is huge. And just in case you’re not sure about exactly what the scientific process is (e.g., you’re having a strong emotional ideological response to my comment), check out this YouTube link before commenting http://www.youtube.com/watch?v=-h9XntsSEro&feature=autofb

    • Hi Phil, did you mean to drop this useful lesson off at AnswersInGenesis and get lost?

      Seriously I don’t think you need to kick things off here with a lesson in hypothetico-deductive inquiry, I find the blog author JR a pretty reasonable and knowledgable guy even though I disagree with his somewhat more explicitly politicized approach to science sometimes. I really think you can just state your case and have a productive discussion.

      As to specifics, I think you’re right, there have been a number of productive lines of research under the banner of evolutionary psychology, including those of the Symons-Buss lineage and alternatives are often less coherent overall. That doesn’t mean every explanation under that banner is equally well supported however. The real value of EP is to me potentially as a unifying framework rather than resting on specific current theories.

      So continue with your case?

      With any luck we can start with good faith, save time, and dispense with philosophy of science 101? ;)

      kind regards,

      Todd Stark
      Philly, Pa. USA
      Nowhere near Dover

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