The Human Beast

Why we do what we do

Are There Universals in Human Behavior?

Or is evolutionary psychology on the ropes?

Karl Popper defined scientific paradigms as shared belief systems. As science progresses, scientists realize that these beliefs are mostly false and move to a new paradigm. In physics Einstein replaced Newton and was superseded by Max Planck Evolutionary psychology follows cultural determinism but its faith in universals makes it vulnerable.

Universals as a challenge to cultural determinism

Anthropologists have always been impressed by the diversity amongst human societies. In one society, all men are restricted to a single wife, for instance whereas in others any number is permitted.

Such variation is commonly advanced by cultural determinists as iron clad evidence for “cultural” differences. The notion is that members of a society put their thoughts together and somehow come up with a set of rules about how to behave, rules that get passed on first by oral tradition, and subsequently by writing and electronic media. Over time these rules change due to accumulated thoughts, such as religious traditions and bodies of law, as well as via random copying error, or drift.

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Evolutionary psychologists attacked such cultural relativism. They proposed that some evolved human characteristics are cross-cultural universals. Men are more interested in casual sex than women are. Or women with a Miss-America type figure, having a curvy waist-to-hip ratio of 0.7 or less, are most attractive in all societies.


The problems with universals

There are three serious problems with basing evolutionary psychology, or any science, on universals. First, the concept of universals is closer to Plato’s philosophy than it is to science. In short, it can be dismissed as more mysticism than science. After all, in the world of biology, all creatures are in continual flux as they adapt themselves to a perpetually changing environment. So the insistence by leading evolutionary psychologists that we are stuck with the (constant) adaptations of our stone-age ancestors is likely bogus.

The second problem is empirical. The constants are empirically testable and do not stand up very well. We now know, for example, that there are several societies where a waist-hip ratio of 0.7 is not perceived as most attractive (1). Even within the same society, the most attractive ratio changes over time. For Miss Americas, the waist-hip ratio has risen significantly over time as less curvy women win (according to my own unpublished analysis).

The notion that women are universally less interested in casual sex might seem more robust. Yet, even this claim encounters problems. Indeed survey evidence indicates that women in some countries are far more interested in casual sex than men in others (2).

Confronted by such evidence, many evolutionary psychologists might be tempted to retreat to the qualification that you have to compare men to women in the same society. This might seem a much safer position. After all if an attractive researcher hails students of the other gender on a college walkway and offers them casual sex, three-quarters of men sign up but no women do, however attractive the male researcher. Now it seems that this research design is badly confounded because women have more to fear from such an encounter than men – being attacked, becoming pregnant, or getting ridiculed and belittled. 

In scenario studies where they feel safe, where their privacy is protected, and where they feel that the man is sexually competent, they are just as interested in sexual pleasure for its own sake as men are (3).

The third problem with universals is that looking for them is a distraction from what I consider to be the much more interesting task of evolutionary analysis – accounting for variation. In this vein, I recently pointed out that humans adopt polygamy (or polygyny) for the same key reasons as birds do: scarcity of males, availability of good territory, and pressure of local diseases (4). This approach is societal adaptationism (or evolutionary social science).

Just because some hypothetical universals fall by the wayside, this does not mean that others cannot stand up, of course. The claim that men value physical attractiveness more whereas women value social status more in a potential mate is probably true. Yet, it is not very scientifically interesting when you consider that appearance matters a lot to women as well as men and they rarely marry a man shorter than themselves. Moreover men rarely marry women who are less educated than themselves, so social status matters for them also.

Instead of focusing on constants, it is time for evolutionary psychologists to take up the challenge of accounting for societal differences. I do not believe that cultural determinism is a credible scientific theory approach here (as I explain in a future post).

On the other hand, the limited work in this field demonstrates that adaptationism can be surprisingly successful at accounting for differences in sexual behavior, crime (5), marriage systems, and much else besides (6).


1. Weisman, A., & Marlowe, F. (1999). How universal are preferences for female waist-to-hip ratios? Evidence from the Hadza of Tanzania. Evolution and Human Behavior, 20, 219-223.

2. Barber, N. (2008c). Cross-national variation in the motivation for uncommitted sex: The impact of disease and social risks. Evolutionary Psychology, 6, 217-228.

3. Paul, E. L., McManus, B., & Hayes, A. (2000). “Hookups”: Characteristics and correlates of college students’ spontaneous and anonymous sexual experiences. Journal of Sex Research, 37. DOI: 10.1080/0022440009552023.

4. Barber, N. (2008). Explaining cross-national differences in polygyny intensity: Resource-defense, sex ratio, and infectious diseases. Cross-Cultural Research, 42, 103-117.

5. Barber, N. (2008) Evolutionary social science: A new approach to violent crime. Aggression and Violent Behavior, 13, 237-250.

6. Barber, N. (2008). The myth of culture: Why we need a genuine natural science of societies. Newcastle-upon-Tyne: Cambridge Scholars Press.


Nigel Barber, Ph.D., is an evolutionary psychologist as well as the author of Why Parents Matter and The Science of Romance, among other books.


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