568 CHAPTER 21Evolutionary biology helps us understand human traits by focusing on our
diversity. People have a remarkable variety of customs, beliefs, and ways of life
(FIGURE 21.24). The comparative method (see Chapters 3 and 16) is one evolu-
tionary approach to understand this variation. We hypothesize that a certain cul-
tural trait is advantageous under some conditions, and compare that trait among
cultures that experience different conditions. For example, if males monopolize
resources required for successful reproduction, we predict that females will some-
times benefit if they bond with a male that already has other mates. That results
in a polygynous mating system—one male with multiple females. This hypothesis
has been tested and supported by comparing species of birds. The prediction is
also supported in human cultures. Polygyny is more common in societies where
wealth is based on cattle and which are typically controlled by males [29, 30, 43]. In
contrast, monogamy is the norm in the agricultural societies of Eurasia, where land
is divided among heirs and not monopolized by a single male [16].
A fascinating but unanswered question is why some cultural traits are widespread
across human cultures. Music and religion are universal, but we do not understand
how or why they evolved. The comparative method gives us power to understand
how differences among populations evolved, but because it relies on variation, it has
limited power to unravel the origin of behaviors and instincts that are universal.
Human behavior results from cultural influences that are overlaid on our bio-
logical tendencies. While those tendencies result from genetic evolution, they allow
an immense range of cultural expressions and individual potentialities. Whatever
the biological foundations of our psychology may be, they do not tell us what we
must, much less what we should, do with our lives.Futuyma Kirkpatrick Evolution, 4e
Sinauer Associates
Troutt Visual Services
Evolution4e_21.24.ai Date 11-02-2016(A) (B) (C)FIGURE 21.24 Wardrobe and technology
are two of the cultural differences among
current human populations such as (A) the
Huli of montane Papua New Guinea, (B) the
Inuit of northern Canada, and (C) urban pro-
fessionals in the United States and western
Europe. (A by D. J. Futuyma.)Go to the
Evolution Companion Website
EVOLUTION4E.SINAUER.COM
for data analysis and simulation exercises, quizzes, and more.21_EVOL4E_CH21.indd 568 3/22/17 1:51 PM