Monday, March 31, 2008

Questions on polygyny and the changing marriage market

A reader has raised a couple of questions. I’ll begin with the first one:

Let's suppose people from other parts of the world move to a tropical environment. Should we expect a shift toward polygynous habits within a couple of millennia under the influence of tropical agriculture?

People would shift toward more polygyny, but they would do so by pushing their envelopes of behavioral plasticity. A couple of millennia doesn’t seem to be enough time to shift the genetic goalposts.

Some 9,000 years ago, Amerindians began to develop agriculture in the tropical New World. These tropical agriculturalists, like the Yanomamo of Amazonia, show the predicted changes in behavior: higher female self-reliance in food production, lower paternal investment, and higher polygyny rates. Between 10% and 20% of all Yanomamo males are polygynous at any one time (Hames, 1995). Nonetheless, this is still lower than the 20-50% we see in sub-Saharan Africa.

It seems, then, that natural selection hasn’t had enough time to create a strong predisposition to polygyny in tropical Amerindians, at least not as strong as what we see in sub-Saharan Africa. In addition, their ancestors may have started off with a very low predisposition to polygyny, having entered the Americas by way of an Arctic environment that selected for high paternal investment. Even in the tropics, Amerindians still have an Arctic-adapted anatomy and this evolutionary conservatism may extend to behavior (Holliday, 1997, pp. 425-426).

In polygynous societies, women choose men. In societies with an unbalanced sex ratio (females>males wise) men choose women. How would you describe the actual state of our society according on this scale?

If we look at reproductive age brackets (20 – 40 years), there are more single men than single women. This is a relatively recent phenomenon and seems to date from the late 1980s. The 1992 U.S. census found the following ratios of single men to single women per age group:

Under 25 – 111
25 to 29 years – 128
30 to 34 years – 121
35 – 39 years – 109
40 – 44 years – 83
45 – 64 years – 64
65 years and over – 30

The imbalance is even greater among 20 to 40 year-olds if we look only at childless singles. It is greater still among white Americans (the black American population has a surplus of single women because of high mortality and incarceration rates among young black men).

Not long ago, the reverse was true. There were more single women than single men in all age groups. If a woman was still unmarried at 25, people considered her doomed to spinsterhood.

What happened? First, the death rate has fallen dramatically among young men. No major wars have occurred since 1945. Highway and workplace accidents have steadily declined. Alcohol is no longer the grim reaper that it once was. Today, so few young men are dying that we now have a serious shortage of organs for transplantation.

Second, divorce laws have liberalized throughout the Western world. It’s now much easier for a man to divorce his aging wife and marry a younger one. And this is the pattern we generally see with second marriages.

Third, it is economically easier, and socially more acceptable, for a woman to have children out of wedlock. Many of these single mothers then drop out of the marriage market, partly because they find it difficult to date men and be a parent at the same time. As well, men are often reluctant to care for children who are not their own, especially if (as is often the case) the woman is not interested in having any more.

In short, marriage-minded men are now in a seller’s market and not a buyer’s market. This is a big change, and one that has aroused surprisingly little comment from social scientists. Yet I see the evidence all around me—the thirty-something man who has a good job, no bad habits, and still no woman in his life. How come? Usually, he’ll duck the question and put on a brave face. Or he’ll blame himself: his low-paying job, his lack of personality, or his looks.

Yet these reasons were not operational when my parents were young—less than a half-century ago. If a man wasn’t married then, it was because he didn’t want to be. Or because he was a ‘bum’ or a ‘psycho’. How times have changed …

References

Hames, R. (1995). Yanomamö, Varying Adaptations of Foraging Horticulturalists, Originally prepared for Just in Time Anthropology series, Prentice Hall and Simon & Schuster, supplemental readings for Ember and Ember's Anthropology, 8th edition.

Holliday, T.W. (1997). Body proportions in Late Pleistocene Europe and modern human origins. Journal of Human Evolution, 32, 423-447.

11 comments:

Anonymous said...

Those ratios seems suspect. For example, under 25, where it is claimed that there are 111 single me per 100 single women.

Since the live birth ratio is around 105 live male births per 100 live female births, and males do kill themselves at a greater rate than females (because more of them are stupid and they have more testosterone), it seems to me that the only way this ratio can be the case is if they are counting immigrant males from south of the border.

There are two issues here then:

1. Most white American females are going to totally uninterested in such men, after all they are hardly interested in the much more marriageable Chinese/Japanese/Korean males.

2. Given that more males than females are in the lower half of the IQ distribution, and female interest in males slightly more intelligent than themselves, there are problems ...

Your analysis is not nuanced enough. For the upper 25% of males in the US, life is pretty rosy, it seems to me.

Anonymous said...

It should also be pointed out that there is evidence that in the west the live male birth ratio is falling. Seems it might have something to do with Hep B being eliminated.

Sampieru said...

Great post, thank you for your interesting response.

About the part 1), I remember that White masters in the Southern states and the Carribean had usually plenty of Black slave lovers. In Louisiana, there was even a small bedroom not far from the master's house where he could meet his lovers. Of course the adaptation in this case is hardly genetic, probably behavioural. Nevertheless it is interesting to see that even white people seem to adapt to tropical environments by having polyginous relationships.

About the part 2) I was wondering whether single-mother governmental aids could explain today's tendencies in mating ?

Before the 60-70's unmarried women in the western world did not receive any help for raising their children. And the society was very critical toward single mothers.
Now, thanks to gov help it is possible (yet difficult) for a woman to raise her children alone, just like in polyginous societies. I mean that men are less "essential" to women and their children's lives than they were before.

Anonymous said...


Now, thanks to gov help it is possible (yet difficult) for a woman to raise her children alone, just like in polyginous societies. I mean that men are less "essential" to women and their children's lives than they were before.


Having the support of a man to help raise your children means the difference between raising a bunch of useless brats and raising a bunch of productive citizens who go to the best schools in the country and can gain entry into high(er) society.

Think about it.

Anonymous said...

Since women usually marry or pair-up with someone a couple of years older than themselves, women from about 24-years old would be married or paired up with someone older than 25.

Over and above that there is the pool of women taken by someone quite older than themselves.

However, there is also the issue that women look for successful men.

Peter Frost said...

"Those ratios seems suspect. For example, under 25, where it is claimed that there are 111 single me per 100 single women."

There are two reasons for the imbalance: 1) A certain proportion of women under 25 marry men over 30 and 2) men are overrepresented among immigrants.

I don't have the reference at hand, but I remember reading that more mmigrant males were marrying native-born females than immigrant females marrying native-born males. This is partly because many immigrant groups actively discourage their women from marrying out. It's also because the physical traits of native-born women are rated positively by immigrant males, even in comparison to women of their own background.

-----------------------------------

"Having the support of a man to help raise your children means the difference between raising a bunch of useless brats and raising a bunch of productive citizens who go to the best schools in the country and can gain entry into high(er) society.

Think about it."


For most human societies, the main goal in life is to have as many descendants as possible. Certain groups (e.g., Hassidic Jews, Hutterites, certain Mennonites)perceive "entry into higher society" as being detrimental to this goal and deliberately discourage pursuit of higher education and individual betterment.

Perhaps you feel sorry for the poor family with a dozen mouths to feed. They, however, may view their situation more positively. After all, whose descendants will be around a hundred years from now?

Anonymous said...


Perhaps you feel sorry for the poor family with a dozen mouths to feed. They, however, may view their situation more positively. After all, whose descendants will be around a hundred years from now?


Well, given the enormous downward mobility we have seen in places like China and Europe, and the effort that successful lineages go to to harass other breeding females, even among other primate species, I suspect that quantity of offspring is not necessarily a good strategy.

Peter Frost said...

"Well, given the enormous downward mobility we have seen in places like China and Europe, and the effort that successful lineages go to to harass other breeding females, even among other primate species, I suspect that quantity of offspring is not necessarily a good strategy."

Uh Europe? The only Europeans with above-replacement fertility are those with a very strong (often religious) commitment to large families. It's certainly not the upwardly mobile.

Tod said...

Fascinating and thought provoking post

Anonymous said...

"In polygynous societies, women choose men".

Actually it seems like the polygynous societies are the ones with the least female choice, where women are married off in their teen years and the unions are arranged by parents.

Anonymous said...

"Actually it seems like the polygynous societies are the ones with the least female choice, where women are married off in their teen years and the unions are arranged by parents."

That's only in the Middle East. In Sub-Saharan Africa its women that do choosing.