by David P Barash
Imagine a Martian zoologist, visiting Earth and observing Homo sapiens for the first time. He, she or it would see a species of primate that differs from the others in many ways, all of them involving our complex cultural, intellectual, linguistic, symbolic and technologic lifestyles. But looking at us through a zoologist’s lens, our observer wouldn’t be especially impressed. To be sure, we have some distinctive anatomical traits (mostly hairless, bipedal, big brains, non-prognathic jaws, unimpressive teeth, and so forth) but being unique isn’t itself unique. Every species is special in its own way.
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.
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