In the comments of this post I mildly disagreed with Eric Michael Johnson that humans are "polygynous" and the relevance of the fact that "estimates range between 5-10% that all children have been sired by men other than a woman's partner." The human monogamy vs. polygamy argument is long-standing, with anthropologists on both sides. Myself, I'm not sure what I believe, because I think binning into two categories is simplistic. In terms of
evolutionary biology societal ideals matter less than the relationship of the distribution of reproductive output of males to females.</b From what I know most cultures have preferred polygyny, but that state is not realized by most men because most men lack the wealth. Additionally, there are other dimensions which need to be explored; West African polygyny where males have looser relationships with their wives, who are independent economic actors, is far different from Gulf Arab polygyny, where women may be restricted to one house under the supervision of male relatives. I'm not going to review the literature of long term male and female effective population sizes, because the area seems confused right now, and I also think there is relevant intercultural variation which needs to be addressed. Rather, I want to focus on a few male lineages which we know of. These are genetic lineages passed along the Y chromosome from father to son where enough textual genealogical data exists to do a cross-check. For example, the Oxford geneticist Bryan Sykes inferred a cuckoldry rate of only ~1% per generation for his family based on th distribution of male haplotypes. That is striking. Perhaps less surprising is that the male descendants of Somerled, Lord of the Isles, married women who were extremely faithful. His descendants were of high status. And this I think fact makes me reconsider the extent of operational cuckoldry in the past few thousand years in many societies. There's a wide range in paternity uncertainty, and it seems that lower socioeconomic groups especially have high rates. Today, fertility is to a great extent inversely correlated with socioeconomic status, but this is probably not true before 1850. Rather, the lower classes often were the descendants of fallen upper classes who themselves failed to replace themselves. In A Farewell to Alms Greg Clark documents this dynamic in England in the early modern era. The existence of such faithful lineages might simply be an artifact of the dominant social structures in Eurasia over the past few thousand years, which were pushed up against the Malthusian limit and exhibited persistent lower class die off (even women who were impregnated by upper class males while their mates were in the fields might not win in the long run unless she could gain resources for her offspring). Of course, I don't know how that might relevant to ancient hunter-gatherers.
