Biological instinct in female to seek out a mate outside of the group.

This isn't confined to humans. Mammals, at least, all (AFAIK) have mechanisms to prevent/discourage littermates/close relatives from breeding. I seem to remember it having a lot to do with smell: a full brother should smell sort of similar, and sister won't put up with hanky-panky from someone like that. Whether this can be extended to smells that you were exposed to as a young child - like an adopted littermate or the toddler next door - I don't know. But it sounds sort of plausible.

Thanks, WK! Your second link leads to a free(!!!!!!) copy of the paper - and it is on a primate that possibly uses odor to 1) prevent incest and 2) promote nepotism.Decoding an olfactory mechanism of kin recognition and inbreeding avoidance in a primate - PMCWhatever it was that I read about this "odor of close kin" issue wasn't about lemurs - but I have no clue as to where I read it.

Clarify that for me just a smidgen, IaJ. Like a tiny bit of context: in Hebrew culture or in Hawaiian?

No, clarify. Not obfuscate.

Show your workings.Better yet, let's work on getting back to the topic of the thread.

Welcome to EvC, Tangle!This adds to the vague bits I posted above - smell having something to do with mating behavior in humans as well as white mice. I can imagine all sorts of research that could be done, but finding a population of undergrad students that would give up all artificial odorants could be challenging.