Sunday 7 April 2013

Clade selection

"Kin selection" and "group selection" are common terms for the way that organisms help organisms which are similar to themselves. I've proposed the term "similarity selection". Another contender is "clade selection". This term came from George C. Williams (1992).

Dawkins said of this:

Williams efficiently disposed of “group selection,” which never recovered (except as a muddled version of kin selection). But in Natural Selection: Domains, Levels and Changes (1992), where he gathered many threads of thought, he developed the important and superficially similar idea (foreshadowed in Adaptation and Natural Selection) of “clade selection” to explain, not “altruism” but macroevolutionary patterns of diversity and - as I would put it - “the evolution of evolvability.”

"Clade selection" seems like better terminology than "group selection" - in some respects. Like the term "kin selection" it puts an explicit emphasis on relatedness. Group selection only works - in the sense of producing group-level adaptations - when relatedness is involved. So: why not use the term clade selection?

Alas, I think there's a good reason not to use the term "clade selection". A clade consists of an organism and all its descendants. The problem is with the "all". You can still have group selection that works without it being clade selection - by the fitness delta involved not affecting all the descendants.

The "all" in "clade" makes "clade selection" a confusing term. Not worthless, perhaps, but I don't think I can endorse the term.

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