Thoughts on Evo-Bio Math and Mesa-Optimization: Maybe We Need To Think Harder About "Relative" Fitness?

post by Lorec · 2024-09-28T14:07:42.412Z · LW · GW · 1 comments

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Does natural selection, in general, really go by inclusive relative reproductive fitness?

Does sexual selection? This seems somewhat likelier.

Obviously there's a trivial sense in which the type of reproductive fitness that natural selection selects for, in general, is not relative. The coarsest denominator, the "bottom-line" aggregate replication rate of DNA-on-Earth, isn't capped as an absolute, and I imagine [although I could be wrong about this?] that the Anthropocene has rapidly increased it [even as "Evolution, in producing humans, may have entirely doomed DNA [LW · GW]" in the long run].

Instead, local aggregate DNA replication rates - whether of the entire biosphere, of the clade Mustelidae, or of the ecosystem constituted by your backyard - are capped in practice by the availability of resources-in-the-environment to those organisms. The extent to which natural selection is modeling aspects of the gene's environment - prey species, predator species, resource-competing species, members of its own species - as adversaries, will of course in the most abstract theory of "what natural selection is" depend, in each local case, on how much each "adversarial" adaptation can marginally be expected to increase the allele's ultimate absolute descendants-cone.

I think biologists have come to think of natural selection, in general, as optimizing - even in theory - directly for inclusive relative fitness, because something like a mesa-optimization daemon which actually does do this even-in-theory, is operating in sexual species - a set-of-conditions for the gene/allele where all aspects of "maximize my descendants-cone" that are not "maximize my share of the species's descendants-cone [which species's replication rate is, from the gene's-eye, abstracted-away as invariant]" are functionally ignored by the main logical engine of mutation.

Biologists and those generally familiar with evo-bio math - I predict - will object to my suggestion that we reframe "inclusive relative reproductive fitness" as an optimization target of sexual selection specifically, on the grounds that it is trivial - of course, since relative fitness as conventionally taken-for-granted - the particular "selfish gene" that implicitly takes its main grounds of likely advancement, as victory in sexual competition with conspecifics - is a sexual-reproduction-confined optimization target, well, biologists already implicitly know not to model asexual cases as optimizing toward that conventionally-understood "relative fitness".

But I think treating this as a mere terminological nitpick, misses a potentially fruitful area of investigation for the question of why sexual reproduction took over at all, threatens to cloud our thinking on this topic in general, and also misses a potential invaluable second non-artificial data point for mesa-optimizer theory [ that is, we might get "natural selection -> sexual selection" AND "sexual selection -> human values", rather than just "natural selection -> human values" ].

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