four things i’ve been meaning to mention about inbreeding and altruism (and other social behaviors). well, i’m sure there’s waaay more than just four things that could be said about the subject, but i’ve got four on my mind (it’s like spinning plates!), so here goes…
1) we’re talking here about the evolution of “genes for altruism” (and other social behaviors) — evolution by natural selection — and evolution takes some time — and depends on what selection pressures are/were involved;
2) given #1, and knowing how biology/natural selection works in general, then there must be different “genes for altruism” (and other social behaviors) — and different types of altruistic (and other social) behaviors — and, like other traits, their presence/frequency probably differs in different populations;
3) inbreeding can make the evolution of “genes for altrusim” (and other social behaviors) easier;
4) inclusive fitness means it pays off to be more altruistic (or more of those other social behaviors) to some individuals than others — i.e. those individuals who share more genes with you. individuals that are more inbred than others ought to show more altruistic (and other social) behaviors to their family members on average than non-inbred individuals since they share more genes with their family members. this should also apply to whole populations (especially considering #3) — however, #1.
points #1 and #3 are why i’ve been so interested in how long a population has been inbreeding or outbreeding. a population is not just going to become more or less altruistic overnight. we’re talking about the evolution of traits — not some magical inbreeding determinism — so there will be some lag-time.
for instance, if you somehow persuaded the entire population of saudi arabia to outbreed as much as possible in the next generation — really shuffle up the extended families there — you would not automatically wind up with a population behaving the way europeans do towards family members and strangers, because whatever “genes (alleles) for altruism” they possess would still be there in great numbers.
you would, however, have altered the conditions in which their altruism genes act, so you would think you would see some differences in behavior patterns. you should, i would think, see some changes in inclusive fitness-related behaviors (#4) since individuals would no longer be sooo related to their family members.
how long would it take to get rid of, or substantially change, whatever “genes for altruism” a population happens to have? i dunno. as you have prolly already figured out, i’m NOT an evolutionary theorist/population geneticist — and i don’t even play one on the innerwebs. (but i do want to be one when i grow up! (~_^) )
where it gets confusing (ok, ok — it’s ALL confusing) is when you realize that the social structure of a population — who is related to whom, and by how much — is not just a product of mating patterns, but is also part of the environment in which humans live and love and try to reproduce successfully.
so you have “genes for altruism” being selected for, or against, due to the conditions in whatever environment in which they’re operating (assuming that they matter at all for the fitness of individuals, which they prolly do) — but, meanwhile, these “genes for altruism” are also partly creating that very environment. talk about a feedback loop!
in other words … it’s complicated.
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