Sometimes it is useful to enter into the record what you think, even if it is not fully formed, or even not strongly held. After reading a review on mutational load in human populations, which lingered long over demographic inferences of our species’ fluctuations in population size, as well as conversations with Gregory Cochran and Ian Mathieson, I have come to the conclusion that cultural group selection is a very important, perhaps dominant, dynamic in explaining the ubiquity of anatomically modern humans over the past ~50,000 years.
This is not a novel position. A group of evolutionary theorists, most prominently today David Sloan Wilson, have argued for the primacy of group level collective dynamics for human societies which allow for a plausible organismic metaphor in their action and behavior for the past 40 years. Peter Richerson and Robert Boyd have developed an extensive body of theoretical work outlining precise models (see Not by Genes Alone) which extend this framework. Importantly, I want to be careful and qualify that I am being precise when I limit my conjecture to humans, and, cultural phenotypes. For empirical and theoretical reasons I believe that humans may be sui generis.
My intuition here is tied in to what I have stated earlier about Aurignacian populations, and their likely extinction in Europe due to the arrival of Gravettian populations. The ancient DNA results are yielding to the conclusion that the human past has been subject to a great deal of local population replacement. To me this is peculiar, because even in the course of inter-group competition one would expect a fair amount of admixture, as is assumed in a demic ‘wave of advance,’ where populations push forward their range through natural increase. In fact the replacements don’t strike me as typically genetical in their fluctuations. Rather, they’re cultural. Punctuated. Alternating between stasis and rapid switches in state and character. The genetic data may simply be witness to the outcomes of winner-take-all outcomes.
Of course there has long been speculation that the social organizations of anatomically modern humans was the key for why they replaced their cousins. Many of these models though were derived from conjecture, and extrapolation. The new twist for me is that the historical population genetics is now aligning with this possibility. These are real concrete data and results.
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