some neat research from a couple of years ago:
Nepotistic nosiness: inclusive fitness and vigilance of kin members’ romantic relationships
“The logic of inclusive fitness suggests that people should be attentive to the mating relationships of their kin — especially their genetically closest kin. This logic further suggests that people will be especially attentive to close kin members’ relationships when a greater indirect fitness benefit is at stake. Three studies tested implications of this analysis. The primary results were that (a) people maintain greater vigilance over (and attempt greater influence on) the romantic relationships of genetically closer kin; (b) this effect is largely mediated by feelings of emotional closeness and perceptions of physical similarity; (c) women are more vigilant than men over their kin members’ relationships; (d) people are more vigilant over the relationships of female kin, as compared to male kin, but only under conditions with especially clear implications for indirect fitness; and (e) people are more vigilant over kin members’ long-term committed relationships, as compared to their casual relationships. These results indicate that a subtle form of nepotism is manifest in people’s concern with their kin members’ romantic relationships.
so, people are concerned about who their relatives mate with (for inclusive fitness reasons) — especially the ones to whom they are more closely related — and especially their female relatives (’cause, of course, women are limited in their reproductive capacity as compared to men, and it’s rather expensive for them [us!], too).
of course, i can’t help but wonder what happens in inbred societies. are these sentiments amplified? like, if your daughter is also your cousin (a few dozen times over), does that make you want to — say — cover her up so she can’t so easily attract a mate? might you want to hobble her so she can’t run off and have assignations with some unknown guy(s)? could you possibly want to cut off her clitoris so she’s not so interested in sex? hmmmmm?
or even if you’re just a little inbred, maybe any guy that wants to mate with your daughter has to ask your permission first. on the other hand, if you’re very outbred, maybe anything goes for everybody.
note (from the article): “Across all three studies reported here, 53% of participants were of East Asian ethnic background, 30% were of European background, and 17% were of various other ethnic backgrounds.”
btw – here’s a little tidbit of info from the lex alamannorum (one of the early medieval germanic law codes): “Chapter 56.1 regulates penalties for violence towards women. If someone uncovers the head of a free, unmarried woman, he is fined with 6 solidi.”
so, early medieval germanic women (single ones anyway) wore a head covering. germanic tribes had endogamous marriage practices, including prolly some form of cousin-marriage, kinda like many muslim societies today.
update 06/25: i think the church may have introduced compulsory head covering for women to northern europeans. here from jack goody’s “The development of the family and marriage in Europe” [pg. 44]:
“In fifth-century Ireland, St. Patrick drew a distinction between the habits of the ‘Romans’, that is Christians, and those of barbarians. In a later canon clerics were told they must conform to civilised Roman practice in three ways: by wearing a tunic, by shaving their heads, and by seeing their wives go veiled.”
(note: comments do not require an email. don’t ask why. don’t be so nosy! (~_^) )
I’d like to see if the result would be the same on family members that are not close to each other, e.g. brother brought up by divorced dad and sister brought up by divorced mom met in their adulthood. See if that inclusive fitness theory still stands…
@theslittyeye – i imagine those feelings wouldn’t reaaly be there anymore if people didn’t know who they were dealing with. then again, who knows? separated siblings are often very attracted to each other and sometimes wind up marrying each other. maybe they would feel strongly about someone so very much like them mating with someone else. -??-
the inclusive fitness side of it would still hold, tho, i think because in the cases where people do know who their relatives are, they are more considered about the mating habits of those relatives more closely related to them.
People are also plenty nosy about their friends. Why wouldn’t they be nosy about their stepsiblings?
@ihtg – oh, i’m sure they would be. but they’re prolly more nosey about actual siblings, that’s all.