Marriage

Monogamy Is Not "Natural" For Human Beings

It's complicated: The imprint of polygamy.

Posted May 20, 2016

Moose pair, U.S. Fish and Wildlife Service, Public Domain
Source: Moose pair, U.S. Fish and Wildlife Service, Public Domain

The idea of mating for life went out with the so-called sexual revolution of the 1960s and books like Open Marriage. So why has monogamy become a hot-button topic, so to speak?

Or has it? Maybe it's just a coincidence that the subject has come up in some of the things I've read lately. Notably, an op-ed piece by evolutionary biologist Professor David Barash, of the University of Washington has written a book on polygamy, and I find his views on the flip-side, being monogamous, equally interesting. In this article, he argues that just because monogamy isn't "natural" to the human species doesn't mean it isn't possible or even desirable. In fact, we often do those things best that don't come easily to us. Playing the violin, for example. 

I'm with him so far, but it gets complicated. We also carry the biological imprint of polygamy, the opposite of lifelong fidelity to one mate. Polygamy is divided into two categories: Polygyny, in which a man has more than one wife, and polyandry, in which a woman has more than one husband. In a humorous aside, Professor Barash explains that the biological benefits of polyandry, one female with multiple males, is not clear. "But that has not dampened many women's enthusiasm," he adds.

The question is if we carry the imprint of polygamy, why does modern society, especially in the Western world, advocate monogamy, which goes against our predilection for multiple sexual partners? Not all animals are sexually indiscriminate, by the way. Although rare, a few species do mate for life and will even reject new alliances after the death of their original partners.

Given that 80 percent of early human societies were polygamous, why did later populations become largely monogamous? Science has no answer to that, apparently, although there are theories, as you might expect. One of them has to do with the "two-parent" advantage to monogamy in caring for the young.

Strangely enough, some creatures in this world can do without the care of any parents at all. Newly hatched baby turtles find their own way to the sea, long after mama turtle has laid her eggs in the sand and departed. Conversely, human babies are completely helpless at birth and need parental care for years afterward. Ergo, in the case of Homo sapiens, two parents are better than one.

Obviously, the benefits of monogamy are not limited to the two-parent child care advantage. I could suggest one or two more, perhaps not within the purview of an evolutionary biologist: Knowing that you always have a date for Saturday night can be a comfort. So can a shoulder to cry on, when you really need one.

Back to Professor Barash. What he calls "the bad news" about polygamy (or harem-keeping) is that, for several reasons, it is not advantageous for humans—male or female. Modern man may dream about the delights of keeping a harem in bygone days, but the truth is that only the sultan could afford a seraglio. The majority of men in those polygamous cultures wound up unhappy bachelors.

Even so, I would argue that there are some today for whom that biological imprint of polygamy seems to provide the stronger, not to say irresistible, urge. I'm talking about the Casanova who shuns commitment in favor of playing the field, and the philandering husband, as well. The idea of mating for life and "forsaking all others" is anathema to them.

Monogamy may not be "natural" for humans, but an awful lot of us still think it's the best choice.