Sociocultural epistasis and cultural exaptation in footbinding, marriage form, and religious practices in early 20th-century Taiwan

Melissa J. Brown; Marcus W. Feldman

doi:10.1073/pnas.0907520106

Edited by Paul R. Ehrlich, Stanford University, Stanford, CA, and approved October 23, 2009 (received for review July 7, 2009)

Abstract

Social theorists have long recognized that changes in social order have cultural consequences but have not been able to provide an individual-level mechanism of such effects. Explanations of human behavior have only just begun to explore the different evolutionary dynamics of social and cultural inheritance. Here we provide ethnographic evidence of how cultural evolution, at the level of individuals, can be influenced by social evolution. Sociocultural epistasis—association of cultural ideas with the hierarchical structure of social roles—influences cultural change in unexpected ways. We document the existence of cultural exaptation, where a custom's origin was not due to acceptance of the later associated ideas. A cultural exaptation can develop in the absence of a cultural idea favoring it, or even in the presence of a cultural idea against it. Such associations indicate a potentially larger role for social evolutionary dynamics in explaining individual human behavior than previously anticipated.

Footnotes

¹To whom correspondence should be addressed. E-mail: melissa.brown{at}stanford.edu
Author contributions: M.J.B. designed research; M.J.B. performed research; and M.J.B. and M.W.F. wrote the paper.
The authors declare no conflict of interest.
This article is a PNAS Direct Submission.
This article contains supporting information online at www.pnas.org/cgi/content/full/0907520106/DCSupplemental.
↵* Gould and Vrba (30) originally defined exaptation broadly as a morphological trait whose (genetic) evolutionary origin is distinct from its current, adaptive function. Currently in population genetics, exaptation has a more focused definition: when a change in fitness of one trait in one set of environments (caused externally to the organism) leads to the sudden importance to fitness of another (possibly genetic) trait previously present in the organism but not relevant or functional. In defining cultural exaptation, we follow Gould and Vrba's broader approach.
↵† There may also be social exaptations: practices that are currently social—i.e., currently associated with a role expectation assumed to be motivational— that were not associated with that social role expectation when the practice was adopted. We do not address them here.
↵‡ Han is the Chinese term for those most Westerners think of as ethnic Chinese. Aborigines are the indigenous Austronesian peoples of Taiwan.