Sex at Dawn

Exploring the evolutionary origins of modern sexuality

Another Bonobo Basher Busted!

Why do bonobos make some people so nervous?

While Ms. Robinson makes some interesting points, many of her underlying messages are inaccurate. A few examples:

  • -- "Sexual utopians can no longer boast about Bonobo nonviolence."

Let's try a mental exercise. Imagine that anthropologists find a tribe of people who never kill one another, never kill their babies, never rape their women, and have no war, never kill other people at all. They're almost completely vegetarian, but sometimes hunt as well. Would you call them nonviolent? They seem pretty nonviolent to me. But apparently, the occasional hunting disqualifies them in Ms. Robinson's view.

Bonobos have never been seen to kill other bonobos, rape, conduct war or infanticide -- either in the wild or in captivity. They occasionally hunt. This makes them violent? For more on the perverse thrill some writers seem to take in "debunking" bonobo nonviolence, see my post here.

-- "It appears that our ancestors' brains changed in order to shift them from standard mammalian promiscuity to pair bonding."

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Oh dear. Promiscuity is not standard mammalian behavior. In fact, the vast majority of mammals are generally non-sexual – only mating during infrequent periods of estrus. There are, in fact, very few species in which promiscuity is normal, or even possible. It just so happens that the two species most closely related to humans (chimps and bonobos) are highly promiscuous. So are we.

Simply being able to have sex any time is very rare among mammals. Known as "extended receptivity," the human female's capacity to have sex whenever she wants is so unusual among mammals that theorists who nervously insist that humans are not promiscuous have twisted themselves into pretzels trying to explain it.

Robinson's claims about the supposed health benefits of marriage have been discussed by our fellow blogger, Bella DePaulo. See this post, for a comprehensive rebuke of these "same old fallacies," for example.

-- "While a promiscuous Bonobo-like culture might sound like utopia for humans, it may be a luxury that only the smaller brained land mammals can afford. Our huge neo-cortex is probably our consolation prize for those pesky, often subconscious, longings for a pair bond. If we were still non-pair-bonders, we'd probably also still have brains small enough to arrive on the planet more fully developed.

The argument here seems to be that large brains are associated with pair bonding and promiscuity is a small-brained approach to sex. This is nonsense. In fact, Robinson herself uses the example of two closely-related vole species, one of which shows pair bonding, while the other doesn't. There may be some subtle genetic differences between these two types of voles related to neurotransmitters, but neither sports a "huge neo-cortex."

Gibbons, the only pair bonding ape, have brains that are significantly less impressive than the promiscuous chimps and bonobos, both of which are considered to be among the most intelligent mammals of all. There is simply no basis for arguing that pair bonding is responsible for increased brain size in our species or any other.

Christopher Ryan, Ph.D., is co-author of Sex at Dawn: The Prehistoric Origins of Modern Sexuality (HarperCollins 2010).

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