EvoluTion And SoCiETy 597
explain polygyny in birds, Monique Borgerhoff-Mulder proposed, and found evi-
dence, that women decide on the basis of the resources they may expect a man to
provide [14]. Human behavioral ecologists do not necessarily assume that a specific
behavior is genetically determined; they may assume, instead, that humans have
evolved the cognitive abilities to respond adaptively to various environmental cir-
cumstances. The response may have been learned, perhaps from a cultural norm,
but this norm is itself adaptive [2].
Complementing this approach, Leda Cosmides, John Tooby, and others have
developed the active (and controversial) field of evolutionary psychology [9, 21, 92,
123]. Evolutionary psychologists propose that over the course of human evolu-
tion, especially during the Pleistocene, specific adaptations, conceived as mental
“organs” or modules, evolved to solve different classes of problems, especially
social challenges such as choosing mates and detecting cheaters. These psycho-
logical mechanisms are assumed (as in psychology generally [83]) to underlie uni-
versal human capabilities that have evolved by natural selection. Some of these
cognitive capacities are highly flexible, enabling people to adjust in novel ways to
novel circumstances.
Some research in evolutionary psychology uses psychological methods to test
hypotheses about the postulated adaptive modules. For example, Cosmides and
Tooby proposed that in social exchanges among unrelated individuals (reciprocity),
cheating is an ever-present threat, so that evolved mechanisms for detecting cheat-
ers should have design features that are not activated in nonsocial contexts [29].
They presented college students with problems that had the same logical form but
different content, and found that the students solved the problem more often if it
described cheating than if it did not. Many evolutionary psychologists use a cross-
cultural approach, on the supposition that a postulated behavioral adaptation that is
much the same among culturally very different populations may be an evolved trait.
For example, David Buss reasoned that because reproduction entails a far greater
commitment and investment of resources by women than by men, women should
have evolved to seek mates who are likely to provide resources, while men, as a con-
sequence of sexual selection, might be expected to place more value on young, phys-
ically attractive mates who are likely to be fertile [20]. This sounds like the epitome
of sexism, yet Buss reported that a large majority of 37 diverse cultures conformed
to the predictions.^4 For example, women are said to value earning potential more
than men do in 97 percent of the cultures, and men prefer women younger than
themselves in 100 percent. Similarly, many of the physical features that are consid-
ered appealing by the opposite sex are consistent across very different cultures, and
some seem to be indicators of reproductive fitness [46]. A match between data and
theoretical prediction is used to accrue support for hypotheses in many evolution-
ary studies, and in science generally. Many researchers do not accept the concept of
mental modules that Cosmides and Tooby introduced, but these are not a critically
important part of a broader evolutionary approach to psychology. Still, it remains
difficult, in many cases, to determine whether human behaviors are best explained
by evolutionary (genetic) adaptation or by cultural effects.
We have seen (see Chapter 21) that evolutionary concepts and some methods
of evolutionary analysis have been applied to cultural evolution. Cultural evolu-
tion and genetic evolution of behavior have been joined in models of gene-culture
coevolution [26, 43], or dual-inheritance theory [16, 99]. At one level, this field studies
how culture affects the selective milieu within which genetic evolution occurs; for
example, lactase persistence has evolved in several cultures with milk-based diets,(^4) An interesting essay that attempts to answer skeptics about this topic is “Yes, but... Answers to
Ten Common Criticisms of Evolutionary Psychology,” by D. Schmitt (https://evolution-institute.
org/wp-content/uploads/2016/03/20160307_evopsych_ebook.pdf).
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