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.
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.
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Um...I was actually saying that humans should not be classified as monogamous, not that they should be viewed as polygynous. I think the high infidelity rate (within a similar range of variation for women as it is for men) could just as easily be interpreted as facultative polyandry. I'm of the view that the human mating system is probably closest to multimale-multifemale. Cultural factors then impose constraints on behavior into the categories of social monogamy or polygyny. I completely agree with you that forcing the entire species into one of the two marriage categories is overly simplistic.
A newer meta-analysis by Martin Voracek confirms that nonpaternity rates are about 2-3%, but also finds that nonpaternity has decreased by almost 1% per decade in developed nations, suggesting that the 5-10% estimate was more accurate in the not too distant past.
I vaguely recall a study done at some hospital, perhaps in the 1950's or earlier, based on blood types, which suggested that a fair percentage of babies born to married couples were not offspring of the husband. I don't recall the exact percentage, but think it was larger than 10%.
Stephen J. Gould wrote a column on the relationship between male and female size and mating systems. The relationship between men and women is such that one would predict a human male mating with 1.28 females. Comment was that that sounded about right.
Monogamy favors weak males and strong females. Polygamy favors strong males and weak females. Civilization is the former, barbarism the later. We mess with Civilization at our own peril.
"suggesting that the 5-10% estimate was more accurate in the not too distant past."
Adultery was a lot easier for farm wives.... except, obviously, if they were named Sykes.
"A study of 2,500 men found that on average there was a 24 percent chance of two men with the same surname sharing a common ancestor but this increased to nearly 50 percent when the surname was rare.
Over 70 percent of men with surnames such as Attenborough and Swindlehurst shared the same or near identical Y chromosome types". Here