BoundedRationality_TheAdaptiveToolbox.pdf

Imitation, Social Learning, and Preparedness as Mechanisms 237
traits such as bird song, sexual imprinting, or habitat selection, which are highly
constrained and have a very specific function. Such traits cannot be regarded as
homologues of the flexible and information-rich vertical transmission system
that characterizes human culture. In contrast to animal proto-cultures, it would
seem that the "traditional" transmission that characterizes human culture ad
dresses a different kind of adaptive problem germane to features of the environment,
which are stable for long periods of time relative to the lifetime of an
individual organism. A comparative perspective suggests that it was horizontal
social learning that evolved first, and that in hominid, and in a relatively restricted
number of other species, a general capacity for vertical transmission
subsequently evolved. Thus the problem of how human culture evolved has
been transformed into two quite separate questions: (a) how did social learning
evolve (where the appropriate focus is on the adaptive advantages of a highly
horizontal transmission system), and (b) how did a highly horizontal system of
social learning evolve into a traditional system with the characteristics of human
culture? Both of these questions have been addressed using mathematical
models.
Figure 13.1, taken from Laland et al. (1996), is an illustration of the results of
a mathematical analysis that used population genetics models to explore when
natural selection should favor horizontal social transmission in a population already
capable of learning. Two key variables turned out to be (a) the probability
that a naive forager will successfully locate a highly nutritional but patchily distributed
food source (e), and (b) the rate at which the environment varies (e), for
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Likely Success of Naive Forager (e)
Figure 13.1 Horizontal social learning is favored by natural selection in changing environments
when the probability of individual foraging success is low, either because individuals
can only search a small section of their environment, or because food sources
are sparsely dispersed. Figure reprinted with permission from Academic Press, Inc.;
taken from Laland et al. (1996).