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PNAS has just published a back and forth discussion between John Skoyles and Deborah Rogers and Paul Ehrlich. John Skoyles expressed beef with the paper Deborah Rogers and Paul Ehrlich recently put out. The jog your memories, Roger and Ehrlich wrote, “Natural selection and cultural rates of change.” I covered that paper in a February post, raising some questions.

I was not alone in my criticisms, Skoyles also had a set. In his letter, “Natural selection does not explain cultural rates of change,” he wonders two things. First, Skolyes addresses whether or not Rogers and Ehrlich established enough of an argument to inferring that natural selection was at play in how canoes design changed. Secondly, Skoyles takes a shot at how Rogers and Ehrlich use the term cultural evolution. Cultural evolution can be used analogous to cultural change or it can be under the principles of natural selection.

Rogers and Ehrlich defended their work in their response, “Reply to Skoyles: Natural selection does appear to explain some cultural rates of change.” Their response is pretty conservative. They write, “although it does not prove that natural selection was at work, it certainly supports that inference.” I still don’t fully see how differences in the rates of change in frequencies of various cultural traits over time infers natural selection, especially when people are the selectors. It seems like another level of selection is at play.

On that note, the University of British Columbia put out a press release on the work of Liane Gabora, who is making a computer model that will piece together the process by which human culture evolves. She’s made some comments that are directly tangential to the discussion between Skoyles, Rogers, and Ehrlich. She says,

“For one thing, artifacts do not change solely through random, ‘mutation-like’ processes. Humans innovate strategically and intuitively, taking advantage of the ability to group items that go together, like mortar and pestle, or use analogies…

…The underlying mechanisms by which culture evolves are superficially similar yet profoundly different from those through which living things evolve. A symptom of this profound difference is that biological evolution prohibits inheritance of acquired characteristics.”

    Skoyles, J.R. (2008). Natural selection does not explain cultural rates of change. Proceedings of the National Academy of Sciences, 105(22), E27-E27. DOI: 10.1073/pnas.0802586105
    Rogers, D.S., Ehrlich, P.R. (2008). Reply to Skoyles: Natural selection does appear to explain some cultural rates of change. Proceedings of the National Academy of Sciences, 105(22), E28-E28. DOI: 10.1073/pnas.0803570105