Sooo....
If I was a pop evolutionary psychologist or sociobiologist I might spend all my time pondering how it's just seed-spreadingly natural for men to want to be polygamous.
Oh, silly, me. Actually if I was a pop evolutionary psychologist or sociobiologist I wouldn't ponder any such thing. I'd take it as axiomatic -- requiring no proof beyond "makes sense to me" -- and cheerfully use that axiom to prove anything else that popped into my little brain. When pressed by people with a modicum of gender-studies in their background I'd blithly breeze by way of explanation that hogamous-higamous, men are polygamous.
The other axiom I'd posit would be that women just don't like sex in the first place, and that therefore they're grudgingly going to aim to have it as infrequently as possible, preferably with as few men as possible. And explain that with higamous-hogamous, women are monogamous. Oh, and bitches too. Oh, or if they didn't match my axiom, whores.
In evolutionary biology, on the other hand, it's more common to actually ponder whether there might be a reproductive benefit or cost underlying any inclination towards something like monogamy.
Something like this tidbit, via from Holly of Self-Portrait as, who says --
...low fertility rates among Mormon polygamists. My favorite bit:
the more women partnered with a man, the fewer children each of those women had. Exactly why is not clear. Like the Soay rams, men may simply not have had the stamina.... The failure of the Utah polygamy experiment should therefore not be seen as that surprising.
Source: Self-Portrait as
Reading the article it sounds like, in fact, on average, women in polygamous marriages tend to have approximately one fewer child for every fellow "sister wife." And no, that's not a stretch. Stories of sultans or Mormon patriarchs notwithstanding, most polygamists have somewhere closer to two to four wives, meaning a one-child per fellow wife isn't going to put anyone in negative numbers.
Anyway, EPs and sociobiologists tend to go on, and on, and on, about how men can fertilize bazillions of women in a lifetime while women's "investment" of pregnancy, lactation, and staying home in the cave-kitchen limits their reproductive potential to a relative handful. And they brass on about how that means men are "naturally" likely to collect wives and partners willy-nilly whereas women are going to just as "naturally" be all gate-keeper-y and discriminating.
Which never made much sense to me -- in the real, non-Flintstones version of "the state of nature" related groups of women with satellite groups of men seems pretty common, and those groups of related women are usually able to collectively gather and trap enough to feed themselves and most of the men. So while women might tend to care about fathers, and be interested in having men in their lives, and definitely interested in the meat and other foodstuffs men tend to hunt and forage for. So in pure reproductive survival terms that's never seemed like a good enough reason to "evolve" a preference for monogamy.
If I were to going to assume that women are "naturally" monogamous, though, and if I were further inclined to go looking for facile sociobiological explanations for why that might be, then the likelihood that getting rooked into polygamy creates a material reduction in women's reproductive potential ought to be just about all I'd need to start making that case.
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Getting back to the original article, the reference to Soay rams is about a variety of sheep that do the whole alpha male head-butting fights over harems thing... but basically run out of sperm. In comments someone pointed out the tendency for women to ovulate in sync. That would tend to put a pretty heavy limit on men's ability to productively"spread his seed" in his own "harem."
Which in turn leads me back to the suspicion that "collecting" wives is probably a relatively recent function of property accumulation rather than some sort of "on the savannah" biological adaptation.
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Note that whereas women (and females of other species) are evidently reproductively harmed by polygamy, there wouldn't necessarily be the same issues with polyamory, either overt or covert. So whereas men might be concerned about "cuckoldry," women (in polygamous marriages anyway) would positively benefit from it. But in monogamy? Not so much -- which at the very least ought to be a monogamy selectivity-stabilizer for men. (Don't hold your breath waiting for a pop sociobiologist to bring that one up.)