Post Author: Bill Pratt
William Tucker, in his book Marriage and Civilization: How Monogamy Made Us Human, makes the case that polygamy and warfare are inextricably linked. Tucker writes:
The hallmark of a polygamous society is that there is always a shortage of women. The Nash Equilibrium is upset and men compete more aggressively for women, since there are never enough to go around.
What is the Nash Equilibrium?
Nash’s thesis, still the mainstay of all game theory, says that a system can reach an equilibrium without maximizing the interest of every individual player. This occurs when the system reaches a point where each player has achieved the best outcome they can under the existing rules. For a large heterosexual group with the same number of males and females, monogamy satisfies Nash Equilibrium. Each player has optimized his or her outcome under the rules of the existing system. More to the point, the only way any individual can improve his or her outcome is by breaking the rules. But this causes other kinds of disruption and works to the disadvantage of the entire group. It can be prevented by other members constantly enforcing the rules.
So how do polygamous societies deal with the deficit of women available for marriage?
In organized polygamous societies the problem is resolved by having men buy their wives. The “brideprice” is the hallmark of a polygamous society, whereas the dowry— an extra incentive attached to an older or unattractive daughter— is the hallmark of a monogamous society. There are no “old maids” in a polygamous society, since women can become second or third or fourth wives of powerful men.
In his 1981 book, A Treatise on the Family, Nobel Prize– winning economist Gary Becker argued that families of young women become the biggest supporters of polygamy because they possess an inherently scarce resource. Love matches and independent liaisons are frowned upon because they risk reducing the brideprice. In order to preserve their market value, young women must be veiled or sequestered and kept out of contact with young men. Because of the difficulties in finding brides, older men with lesser means are forced to look among younger and younger cohorts. Child marriages become common. Given the degree of sexual inequality and the great age differences that result, the personal bond between husbands and wives is not strong and there is very little companionate marriage.
So where does warfare enter the picture?
For primitive tribes, however, there is always one way of resolving this dilemma— raiding neighboring villages for their women. Academic anthropologists often have great difficulty dealing with this. In Marriage, Family, and Kinship, a book published in 1983 by the Human Area Relations Files at Yale University, for instance, Melvin and Carol R. Ember conducted a study that looked for correlations between polygamy and male-female imbalances. “[I]t appears that the cross-cultural evidence is consistent with the old notion that polygyny may generally be a response to an imbalanced sex ratio in favor of females,” they wrote.
What creates the imbalance? “It appears that an imbalanced sex ratio in favor of females may be produced by warfare that results in a high mortality rate for males.” They parsed the data looking for correlations between high rates of warfare and polygyny and sure enough, there it was. “[W]e find that a high male mortality rate in warfare is fairly strongly associated with polygyny. . . . In sum, it seems that the cross-cultural evidence presented here is consistent with the theory that societies with a high male mortality in warfare are generally likely to have an imbalanced sex ratio in favor of females and, presumably for that reason, are likely to practice polygamy.”
The Embers argue that “warfare kills a lot of men and leaves a surplus of women. The only way to make sure everyone is married is to allow polygamy.” Tucker believes the causal relationship posited by the Embers is exactly backwards.
Societies that are polygamous to begin with go to war precisely because they have created an imbalance by letting each man take more than one wife. This creates a demand for more women that can only be resolved by stealing women from other tribes. Thus warfare and polygamy become mutually reinforcing.