by David P Barash at Aeon: Among our catalogue of not-so-special traits would be the fact that men are on the whole larger than women: about 7 per cent taller and 15 per cent heavier, with this difference somewhat greater when it comes to muscularity. Also notable: men outnumber women when it comes to lethal violence by a factor of roughly 10:1, a differential found not only cross-culturally among adults, but even recognisable among young children (as a proclivity for violence).
Given these facts, our zoologist would strongly suspect that these humans are paradigmatic harem-holding mammals, notwithstanding the fact that, in the Western world at least, monogamy is the designated standard. In our sexual dimorphism (physical and behavioural male-female differences), we fit the normal polygynous profile for all other animal species. This profile arises as a result of sexual selection, whereby males compete with other males, and more fit males garner a payoff of enhanced reproductive success via an increased number of sexual partners.
This diagnosis of polygyny would be enhanced if the observer visited a high school: girls are physically and socially more mature than same-age boys (to the consternation of both). This pattern, known as sexual bimaturism, is also a polygyny give-away, if rather a counter-intuitive one. In order to reproduce, women undergo considerably more physiological stress than do men; they must nourish an embryo in utero, give birth and then lactate. By contrast, men need only produce a few cubic centimetres of semen. One might expect that males would mature sexually earlier than females since so much less is required of them, but this is not the case. In polygynous species, males must participate in fierce same-sex competition if they are to reproduce at all. Woe betide a male who enters the reproductive arena when too young, small, weak and inexperienced. Just as the degree of sexual dimorphism maps very closely upon the degree of polygyny (average harem size) in a species, the extent of sexual bimaturism is also strongly correlated with the extent to which males compete with each other for access to females. Humans fall into the moderate polygynous part of that spectrum.
Evidence for human polygyny is not confined to physiological differences. Prior to the cultural homogenisation that came with Western colonialism and missionary coercion, more than 80 per cent of traditional human societies were preferentially polygynous. Moreover, genomic data tell the same story: there is considerably more variation when it comes to mitochondrial DNA, which is inherited only from mothers, than in Y chromosome DNA, bestowed upon subsequent generations exclusively by fathers. In other words, over the evolutionary history of Homo sapiens, a relatively small number of men produced children with a relatively large number of women. As a species, we have had a greater variety of mothers than of fathers.
Put this all together, and the result is clear. An unbiased extra-terrestrial observer would consider that Homo sapiens’ polygyny is simply undeniable. Case closed.
But the likely insights wouldn’t stop there. Anyone sufficiently disentangled from the unconscious biases we all suffer from might well note that humanity’s polygynous heritage doesn’t only influence how men and women behave toward each other, notably aspects of aggression, parenting and sexuality. It also explains one of our species’ most important imaginary creations: monotheistic religion.
More here.
