Scientists clash over origin of monogamy

Humans, along with prairie voles, grey-handed night monkeys, jackals and coyotes, are numbered among the 9 percent of mammals who are socially monogamous. Can evolution provide an answer?
Denyse O'Leary | Aug 14 2013 | comment  

Scientists investigating the evolutionary origins of monogamy have drawn conflicting conclusions, it was reported last month. No surprise to married folks, that’s for sure. But seriously …

Two separate computer simulation studies recently reached opposing conclusions about why monogamy evolved in primates (humans, apes, monkeys). When discussing the disputed matter, the researchers made clear:

“We’re very cautious about extending our conclusions to humans… Humans are so very unusual because they have culture—and that changes things.”

Which didn’t stop Carl Zimmer at the New York Times, who happily burbled,

“Even with the scientific problem far from resolved,… research like this inevitably turns us into narcissists. It’s all well and good to understand why the gray-handed night monkey became monogamous. But we want to know: What does this say about men and women?”

What it actually says about men and women is precisely what the researchers cautioned: nothing much, because culture “changes things.”

That is, whether a given culture favours promiscuity, polygamy, monogamy, same-sex unions, or celibacy depends largely on answers to the question, how should we live? Apes and monkeys no more ask such a question than dogs or cats do because what they are determines how they live.

Humans are fated to ask, which is the way? Then: Why are we following this path and not another? Whose path is it?

Followers of the Darwinian tradition of human nature do not like to admit of any distinction between humans and animals. As a result, they expend considerable trouble trying to explain how monogamy evolved (the “evolutionary puzzle” of monogamy).

In the dispute noted above, a group at the University of Cambridge claims monogamy started when “females” travelled more widely and “males” needed to keep track of them n order to mate. A group at University College London claims that “males” wanted to protect the future of their selfish genes by preventing the infanticide of their offspring by other males (sperm competition). As always with these theories, the mind-free selfish genes are supposed to know what they are doing better than any whole entity does.

Indeed, in Zimmer’s account, we learn that human brainpower actually evolved from monogamy:

“The extra supply of protein and calories that human children started to receive is widely considered a watershed moment in our evolution. It could explain why we have brains far bigger than other mammals.”

Brains, we are told, consume twenty times the calories of muscles.

Such “pop science” speculations often frustrate scientists who don’t doubt that evolution occurred. Paleoanthropologist John Hawkins responded to the claim that eating meat makes humans smarter by asking, “Is it a magical meat property? If I fed enough meat to the local deer, would they get smarter?”

The problem with that type of speculation is this: the researchers are hunting for a single, incidental cause of humanity. They cannot acknowledge a series of hundreds of interlocking, interdependent, and complementary causes because that would amount to a design, and all talk of design is forbidden.

But none of the supposed individual causes really works by itself either. So the otherwise estimable researchers are stuck with a variety of contradictory explanations that provide no clear or comprehensive picture.

With marriage and family, studies of the ancient human past generally speak with many, conflicting voices. One problem is that the further we get from physical or—much better—documentary evidence, the more contradiction or uncertainty we encounter in the story of human origins.

For example, some authorities tell us that men roamed and women homed. But others say, based on skulls and teeth, that “ancient hominid males stayed home while females roamed.” Some claim that ancestors of humans mated as did chimps, but then everything changed. We also hear that at Çatalhöyük in Turkey during the Stone Age, people did not appear to live in families. This claim arises from the fact that people buried beneath the floors of houses were not closely related. Trouble is, we don’t know how certain individuals were chosen for floor burial in certain homes. The decision may have been based on factors lost to us.

There are only a few things of which we can be certain, and it is not clear that evolution sheds any light: Polygamy almost always means, in practice, one man having more than one woman. Whether polygamy is permitted or not, most individuals must be content with one spouse (or none). Generally, women’s rights fare better in officially monogamous societies. When we try to go beyond that, we find ourselves in a wilderness of speculation, past and present.

Denyse O'Leary is co-author of The Spiritual Brain

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