The evidence of polygamy is in our genes?!? Poor Science writing and the danger of sociobiology

The Washington Post recently reported on a genetic study that found more genetic diversity in female ancestors than male ancestors. The article was headline:

The evidence of polygamy is in our genes

The article explains the finding:

In the genetic history of our species, the mamas outnumber the papas. A new study in Investigative Genetics reports that females have made a bigger contribution than men.

By studying the DNA of 623 males from 51 populations, the researchers found more genetic diversity in the DNA inherited from mothers than they did in the DNA inherited from fathers.

At first glance, these results could be taken to mean that there used to be more women than men. But if you know anything about history, it makes more sense to blame reproductive habits: In many cultures, more women reproduced than men.

And then it goes off the deep end of speculation via sociobiology (a field based on the assumption that social behavior has resulted from evolution and is sometimes used to justify such behaviours):

Polygamy —  the practice of one man marrying multiple women — was historically pretty common (and probably much more common than the opposite group marriage arrangement, polyandry). If most men have multiple wives, and the richest can support a whole bunch, that’s going to leave some men without reproductive partners. So even though an individual male might have had more offspring than most individual women, the gender as a whole was making fewer contributions to the gene pool.

How we get from the fact that more women reproduced than men to any information about marriage in prehistoric people is a bit beyond me. First, (and I know this may be a shock here) people can reproduce with out being married. In fact whole societies may have had no marriages at all and still produced the pattern of more females reproducing than men. It is not like we found a huge stack of marriage certificates from 10,000 years ago and saw individual men married to multiple wives. But if you are looking at reproduction as marriage (an unscientific approach perhaps biased by living in  today’s 1950s society), then you might miss a more obvious answer. (At least this is what I thought of).

Prehistoric women probably had enormously high rates of dying in childbirth (validated by many scientific studies). That alone could account for the effect of more women reproducing than men, if men took up new partners when their partners died.

But you won’t see that if you are looking to justify the cultural idea that men are polygamous but women aren’t polyandrous.

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2 Responses to The evidence of polygamy is in our genes?!? Poor Science writing and the danger of sociobiology

  1. jkshapiro says:

    Strictly speaking, polygamy is the umbrella term for polyandry and polygyny. If they’re mentioning one term they should mention the other.

  2. Marcia Beck says:

    Love this. All too often we mistake our own world views as ‘truth’ and then apply these views to others. But to call it science is irresponsible and even dangerous.

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