THE EVOLUTIONARY STORY OF HOMO SAPIENS 567
What caused this cultural explosion? The enormous change
in the capacity for culture was made possible by evolutionary
changes in the brain that may have occurred much earlier.
But the cultural elements themselves, such as paintings on
cave walls, do not evolve by changes in allele frequencies. Just
as genetic evolution begins with a single mutation, change in
cultural elements—cultural evolution—begins with a single
variant. These cultural “mutations,” or memes, spread by dif-
ferent rules than do genetic mutations [4, 7, 66]. Most important,
cultural traits can spread quickly by horizontal transmission,
that is, between individuals of the same generation. Horizontal
transmission does occur rarely with genes (see Chapter 4), but it
can be orders of magnitude faster with cultural traits. Politicians
and advertisers exploit that fact in efforts to convert the opinion
of an entire population in less than one generation. In many
ways, the horizontal transmission of cultural traits resembles
that of a disease more than the inheritance of a gene. It is no
coincidence that we say a video can “go viral.”
A second key difference between cultural and genetic
inheritance concerns the forces that cause traits to spread. A
genetic mutation spreads by natural selection if it improves
fitness. Many cultural innovations, however, spread with no
help from natural selection, but because they are preferentially
copied or learned. This results in biased transmission. Indi-
viduals can imitate a behavior because of its content (e.g., it is
perceived to be advantageous, or is simply easy to remember),
because it gives psychological rewards (e.g., consuming alco-
hol), because of features of the individuals who already exhibit
the trait (e.g., copying prestigious or successful persons), or
because people prefer to conform to the norm. Consequently,
not only useful traits, but also traits that decrease fitness, can
spread. Tobacco and alcohol decrease survival and fertility,
but both are used by societies across the globe. Smoking and
drinking are socially attractive and physiologically addictive.
In evolutionary terms, those behaviors spread because they
have an advantage in horizontal transmission, not because they increase fitness.
A third way in which cultural and genetic inheritance differ is that at least some
“mutations” can be intentional. Over much of human history, many of the cultural
variants that spread and became the norm in particular populations were not con-
sciously planned, but others were, such as improvements in tools. In the modern
world, cultural mutations are intentional more often than not. Unlike the mutation
that causes lactose tolerance in adults, the next version of the Internet will not
appear at random.
Cultural evolution also happens by processes that are similar to those in genetic
evolution. The frequencies of cultural variants may change by random fluctuation,
or “cultural drift” (e.g., the few practitioners of a special craft in a small population
may die before having trained apprentices). Cultural differences among groups,
such as tribes, can evolve by group selection. Group selection can be more effective
in cultural than in genetic evolution because cultural traits are often very homo-
geneous within groups, since group norms may be forcibly maintained. Some reli-
gious cultures, for example, have been maintained not only by the inheritance of
parents’ beliefs, but also by policing (think of the Inquisition) and by social exclu-
sion of nonconformists.Futuyma Kirkpatrick Evolution, 4e
Sinauer Associates
Troutt Visual Services
Evolution4e_2123.ai Date 11-02-2016(B)(A)FIGURE 21.23 Sophisticated culture in human societies began
more than 50 Kya. The magnificent cave paintings found in
France and Spain date from 30 to 10 Kya. This painting is from
Lascaux, France. (B) The earliest flutes, made from the bones of
bears, birds, and mammoths, are about 40 Ky old. These are from
Hohle Fels cave in Germany.21_EVOL4E_CH21.indd 567 3/22/17 1:51 PM