An interesting paper by Deborah Rogers and Paul Ehrlich was published online in PNAS today. The authors examine rates of change (evolution) in functional vs. cultural characteristics in Polynesian canoes, and turn up interesting (though not exactly surprising) results. Their study found that functional characteristics (things that affect survival/trip success) change fairly slowly relative to cultural (“aesthetic, social, and spiritual decorations”) characteristics (p. 2/5). Such a finding is similar to the results of studies of genetic evolution: functional traits/loci that are important for survival tend to be conserved, while traits/loci that under normal circumstances do not affect fitness (neutral) tend to evolve more rapidly.

The authors suggest that their data support studying culture change in an evolutionary perspective, a position that has been debated in anthropology’s past. Dare I say the T-word, this is because of a historically teleological view of evolution, viz. that if creatures (and cultures) evolve, then there are better and worse trajectories, optimal physical or cultural states. Of course, all evolution means (generally) is the accumulation of differences over time. Futuyma (1998) defines it, “In a broad sense [as] the origin of entities possessing different states of one or more characteristics, and changes in their proportions over time” (p. 767). So the occurrence of cultural evolution shouldn’t be controversial, and is pretty well established. Just as in biological evolution, the authors provide a cultural example that “natural selection apparently slows the evolution of functional structures whereas symbolic [neutral with regard to fitness] designs can evolve more rapidly” (Rogers and Ehrlich 2008, p. 1/5).

It is interesting that the authors regard “spiritual” design elements as having “presumably…no differential effect on survival from group to group” (p. 2/5), because the individuals making them probably thought spiritual designs would have conferred survival benefits. But, hey, maybe people utilizing effective ‘functional’ designs might also tend to use certain ‘spiritual decorations,’ causing linkage disequilibrium of traits–just like in genetics! Another genetic analogy is the authors’ finding that symbolic traits can evolve more rapidly, possibly by “cultural selection,” as a means for culture-groups to differentiate from each other. This reminds me of a study of those damned Drosophila spp. that found greater prezygotic reproductive isolation in sympatric species than in allopatric ones (Coyne and Orr 1997). Ok, it’s not a perfect analogy, but it’s close enough for me.

One could draw myriad analogies between culture change and biological evolution (ooh, how about cano-evolution in small vs. large populations…), but these might simply be indicative of general rules of change in dynamic systems (like, say, culture and biology). Changes that drastically negatively affect a system ought not last very long (i.e. be selected against), lest the entire system cease to be (I know, I just said, “lest”). Changes with no effect on a system ought to occur fairly regularly and remain in or disappear from a system simply by chance (drift, Neutral Theory). And changes that make something better ought to increase in prevalence (be selected for, like color screens in iPods, adaptive copies of MCPH1, sturdy canoes). Change has become the only thing I know I can expect, and it is exciting to see the predictions of evolutionary theory are effective in other areas. Maybe now I have a milieu wherein I can further develop my theory of Sensual Selection…

References
Coyne JA and HA Orr. 1997. “Patterns of speciation in Drosophila” revisited. Evolution 51: 295-303.

Futuyma D. 1998. Evolutionary Biology, Third Edition. Sunderland: Sinauer Associates, Inc. [see p. 25 for an unforgivably awesome picture of Sewall Wright]

Rogers DS and PR Ehrlich, in press. Natural selection and cultural rates of change. Proc Nat Acad Sci xx: 1-5.