Let’s say you are a typical young woman living in a polygynous society, like Uganda, and some nice married man starts trying to woo you.  How eager would you be to become wife number 3, as compared to holding out for that one-woman man, who will love only you?  

Now let’s say you were a typical young fellow living in the United States 100 years ago, and you were looking to find yourself a nice gal to settle down with, and start a homestead.  But you don’t have much money in the bank.  Are you completely out of luck? 

The answer to both questions depends on some simple principles of biological supply and demand.  First thing you’d want to know is how saturated the market is.  In particular: How many other members of your sex between the ages of 15 and 50 are out there? 

Thomas Pollet is an evolutionary psychologist at VU University Amsterdam.  Along with University of Newcastle’s Daniel Nettle, he has conducted a fascinating program of research applying the idea of “biological markets” to human mate choice.  

The idea of biological markets was originally put forth by two economically oriented biologists (Noe & Hammerstein, 1995).  A biological market governs exchanges between individuals who are offering different commodities, as in the case of human mating, in which females offer fertility whereas males offer resources.  As in other marketplaces, the value of a commodity depends not only on its quality, but also how scarce it is, and how many other individuals are offering it.  At a farmer’s market, blueberries, apricots, and avocados are all cheaper when they are in season, and lots of vendors are competing for buyers.  Likewise, the marriage value of a man depends not only on his resources, but also on how many other men are available as potential husbands. 

To examine how the biological market in mates plays out, Pollet and Nettle have mined a number of fascinating data sources, connecting statistics on marriage to various economic indicators in countries around the world.  For example, they examined census data for over 1 million men in five districts of Uganda, where some blokes marry more than one woman, and some other poor fellows consequently get left out in the cold.  From the perspective of biological economics, an additional wife benefits a man’s reproductive fitness, since each new wife can bear additional children, thus increasing the number of genes he contributes to future generations.  For a woman, polygyny is less of a good deal, since each new wife further divides the man’s resources.  Compared to women in monogamous marriages, women in polygynous marriages have fewer children, and they fare less well in terms of growth and survival rates.  For the husband, those costs are more than offset by the additional fertility of a new wife.  For the wife, she may be willing to pay the costs, though, if there are not a lot of good men on the market, and if her potential husband has a lot more resources than his monogamous competitors. 

In keeping with the logic of biological markets, polygyny is more common in areas with more women, so that men are in a buyer’s market.  As the numbers of men increase, women’s standards go up, and it becomes increasingly important for a man to have economic resources to offer.  Indeed, as the number of men went up, men who were landowners did increasingly better at finding wives than did their poorer competitors.  Hence, poor men do especially badly when there are a lot of men on the market, whereas having land more than doubled a man’s chances of having more than one wife. 

Pollet and Nettle found additional support for the idea of biological markets when they analyzed data for 21,973 men from the 1910 United States census.  In general, men who had high status jobs back in the good old days were more likely to be married than men with low status jobs.  But a man’s status mattered most when there was a male-biased sex ratio, and thus a lot of fellows out there competing for a few good women. 

In an earlier blog, I noted that sex ratios in modern China are becoming increasingly male-heavy (see: The cost of a woman versus the cost of a man).  One consequence of this is that Chinese men are having to pay high bride-prices, and that men without economic resources are out of luck.  In another earlier posting, I noted another facet of this issue: guys who live in areas with too many men need to start flashing more of their cash (see: How would more women help the economy?

So the upshot of all this is that if you’re a fellow without much money, you might want to consider migrating to one of those places like New York City, where there are more single women than single men.  You’ll have to come up with some cash for the ticket, though.  

Douglas T. Kenrick is author of Sex, Murder, and the Meaning of Life: A psychologist investigates how evolution, cognition, and complexity are revolutionizing our view of human nature.  He explores the evolutionary side of economics more deeply in his upcoming book: The Rational Animal: How Evolution Made Us Smarter Than We Think.  (coauthored by Vlad Griskevicius, and due out next fall from Basic Books)

Related blogs: 

Does a woman’s company always cost more than a man’s? Behavioral economics meets bride-price, dowry, and prostitution.

The cost of a woman versus the cost of a man: What do women pay for in a man? 

How would more women help the economy?  The economic consequences of too many men.

Deep Rationality: Evolutionary psychology meets behavioral economics.


Noe, R., & Hammerstein, P. (1995). Biological markets.  Trends in Ecology and Evolution, 10, 336-339.

Pollet, T.V., & Nettle, D. (2007). Driving a hard bargain: sex ratio and male marriage success in a historical US population.  Biology Letters, 4, 31-33.

Pollet, T.V. and Nettle, D. (2009). Market forces affect patterns of polygyny in Uganda Proceedings of the National Academy of Sciences of the USA 106: 2114-7.

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