Wednesday, 28 January 2015

A persistent group selectionist hangover

Cultural group selection has led to much confusion. One of the associated confusions is the idea that group selection is more prevalent in the cultural realm than in the organic realm.

This idea appeared prominently in "Not By Genes Alone". Here's what Boyd and Richerson wrote back then:

The real scientific question is what kinds of population structure can produce enough variation between groups so that selection at that level can have an important effect? The answer to this question is fairly straightforward. Selection between large groups of unrelated individuals is not usually an important force in organic evolution. Even very small amounts of migration are sufficient to reduce the genetic variation between groups to such a low level that group selection is not important. However, as we will explain below, the same conclusion does not hold for cultural variation.

It is correct that selection between large groups of unrelated individuals is not usually important. However it is wrong to say that this conclusion does not apply to cultural variation. There the relevant 'individuals' are bibles, dollars and iPhones. These cultural individuals are often related with r~=1. Without relatedness kin selection doesn't work - and neither does group selection.

The idea that group selection works better in the cultural domain has been knocked around by various group selection advocates since then - apparently in an attempt to make cultural group selection seem more plausible. The idea is also beloved of those who like to exaggerate the differences between the cultural and organic realms. The latest endorser of the idea is Razib Khan - in his recent article Language (Culture) and Genes Evolve Differently. Razib gives the following rationale:

Not only is there a great deal of horizontal transmission, but cultural processes are subject to a greater “mutation” rate, and selection can be much more efficacious. The latter is why group level selection is more mathematically plausible for culture than genes; competing demes can be much more distinct in culture than genes because minimal gene flow can equilibrate biological differences, while biased transmission of culture can result in insulation of different groups from homogenization (e.g., inheriting your cultural traits from your father, rather than your mother, who may have been kidnapped from an enemy tribe).

To be plain, there's no supporting evidence for the idea that cultural group selection is any more prevalent than organic group selection. The whole idea is one of the fantasies introduced by group selection advocates.

The now widely-recognized broad equivalence of kin selection and group selection should have obliterated this fallacy - since kin selection is clearly broadly applicable to both realms - and it is patently false that kin selection doesn't apply to the organic realm - as Boyd and Richerson originally claimed for group selection.

In fact, both the organic and cultural realms exhibit superorganisms, eusociality - and all manner of milder forms of kin selection.

Why does the idea that group selection applies more to culture than to the rest of biology continue to lead a zombie existence - long after it has lost any sembalance of a credible empirical or theoretical basis? It isn't clear. Cultural lag is probably involved. Anyway, this article is here to drive another nail into the coffin of this dud idea. R.I.P.


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