Among orangutans, it was commonly thought females prefer the large studs to the less-endowed males. So the small-built guys have only one choice: coercion. Rape under these circumstances made perfect sense until biological anthropologist Cheryl Knott investigated further.

She found female orangs sometimes resisted the flanged hunks and willingly mated with the unflanged males. What’s going on here?

Not all large orangs are studs; some of them may be over the hill. While resisting such males, females may copulate with small males to save their babies.

In many primate societies, as soon as a male takes over a territory by ousting the dominant male, he goes on a baby-killing rampage. Bereaved mothers come into heat, and the new male sires his own offspring. Knott conjectures female orangs are somehow able to sense when small males are on the threshold of gaining dominance, and mate with them. When they gain power, the new lords might spare the newborn if they thought it was theirs. But then infanticide is unknown among orangutans, so what drives female orangs to mate with smaller males?

To add to the mystery, female orangs sometimes start out protesting but cooperate later in the same sexual encounter. Or, alternately, they appear to consent and then resist. Could these cases be called rape? Much remains to be studied and interpreted of orangutan mating strategy.

So why does rape occur in Homo sapiens?

Ever since evolutionary biologist Robert Trivers came up with the ‘conflict of interest between sexes’ theory in 1972, many theorists have cited it to explain rape. Since little energy is required to produce sperm, men can maximize the number of their offspring by inseminating as many women as possible. Women, however, are pregnant for nine months, and produce one baby at a time generally. Babies are born helpless, and mothers spend a considerable amount of time providing care. Naturally, women are fussy about finding the right mate, rather than indiscriminately sleeping with many men. According to Trivers’ theory, this irreconcilable conflict between men seeking quantity and women wanting quality apparently leads to rape.

If this conflict is such a big deal, you would think human society would be polygynous, men taking multiple wives. Would such a society be less rape-prone? But what led many human societies across the world towards monogamy? It is practised in modern industrialised societies, sedentary farming communities, and amongst nomadic hunter-gatherers. The very fact most of us opt for a single spouse at a time indicates there’s something else going on here.

According to cultural anthropologist Joseph Henrich, when a few men take many wives, other men are deprived of mates. Similar to ducks. The intense competition between men for the remaining women undermines society, resulting in more murder, rape, violence, kidnapping and poverty.

Counter-intuitively, our societies opted for monogamy, with some clandestine affairs on the side, to minimise rape as well as other crimes. That’s a rare phenomenon — only about five per cent of mammals are monogamous. And still, we are grappling with rape.

Until the 1970s, biologists argued that men raped when they could get away with it, and their coercive tendencies were passed on to the next generation. Was rape a hereditary behaviour then?

In 1975, feminist Susan Brownmiller came up with a radically different perspective. She said rape is used by “all men [to] keep all women in a state of fear” [emphasis in original].

Taking their cue from there, psychologists and feminists have argued that rape was a display of male power and dominance over women. According to them, rape was a learnt behaviour.

In their 2001 book, A Natural History Of Rape, biologist Randy Thornhill and cultural anthropologist Craig Palmer suggested men rape when they don’t have status or resources to attract mates.

That sounds like the mistaken belief that small-built male orangutans rape because females don’t desire them.

(This is part two of a four-part series)

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