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Marital infidelity has been in the news quite a bit lately. As women wondered why Hillary stuck around when it was found that her husband Bill had been on the prowl, women wonder why Mrs. Spitzer stuck with her husband after he'd been found to have been playing around. The reasons a particular woman sticks with her husband are varied and complex, but much of what men and women do is grounded in our basic wants and needs.
The introduction to this series discussed the weakening of many laws and customs which encouraged men to help women raise children and the first article in the series introduced the idea of natural selection affecting the ways in which men and women interact. Although it's hard to imagine how things were before the industrial revolution, the key point is that women aren't strong enough to farm and they can't hunt because crying babies scare away the game.
In a muscle-powered farming or hunting society, the only way a woman can avoid starving is to find some man who'll feed her. Women who starved had fewer children than women who didn't starve, so natural selection favored women who could persuade men to feed them and favored men who were willing to feed women.
Now that our society is wealthy enough that women can support themselves, they no longer have to hang around with men unless they want to. It appears that women like Hillary and Mrs. Spitzer would rather stick with their men than leave, but they certainly aren't very happy with how their relationships with men have worked out.
It's surprising to realize how much has changed in our society. The common American view of divorce as no big deal is nearly universal in newspapers and on TV. It's hard to believe that as recently as the 1960's, employers often fired divorced men, saying, "If you can't keep your promises to your wife, you can't keep your promises to the company." As Jack Benny put it, "My wife Mary and I have been married for forty-seven years and not once have we had an argument serious enough to consider divorce. Murder, yes, but divorce, never."
Modern men and women don't seem to think much about how their wants and needs have been shaped over time. Women have rather unrealistic ideas about men, and vice versa. Basing relationships on how you wish the other party thinks won't work as well as basing what you do on how the other party really thinks. The goal of discussing natural selection is to help men and women understand their underlying drives so that they can relate successfully to each other.
Natural selection doesn't distinguish between right or wrong. It doesn't care whether you're happy or miserable. Natural selection only cares how many children you have and whether they have children of their own. If you have lots of children who have children, your genes are passed on which makes you a "reproductive success." If you don't have children who survive, you're out of the game.
Let's look at some of the tendencies that natural selection favored in men and in women back when our ancestors lived on what they could find or farm.
Being big and strong makes it possible for a man to feed a woman well by either hunting or farming and makes it more worthwhile for a woman to have his child. A pregnant woman walks the valley of the shadow of death; having babies in a non-medical society is dangerous.
Having the child of a weak, sickly man risks her life just as much as having the child of a strong man, but the child of the strong man is more likely to live. Thus, a woman gains an advantage if she can attract a strong, healthy man to get her pregnant. It's even better if he's willing to hang around and feed her.
Women have been attracted to strong, healthy, athletic men for millennia. Assuming he sticks around, a strong man is more likely to live the 20 years it takes for a woman to get her children old enough to survive by themselves. Women like long-term relationships - a one-night stand can leave her holding the baby.
As societies develop from being nomadic to settling down in an agricultural setting, women are attracted to men who own land. Women know very well that land ownership suggests the ability to protect and feed a woman and her children. Land ownership has been the basis of wealth ever since people started farming, and most wars are fought over land.
What about intellect? In a primitive society, intelligence is of little use. Even a genius can't invent a labor-saving machine if he has to spend all day every day shoving a plow to get the next meal.
Intellect is useful only as the society progresses enough that there can be a land-owning "leisure class" who have time to think about something beyond tomorrow's meal. Being as smart in warfare as Genghis Khan was can help with reproductive success. National Geographic suggests that he has 16 million living descendants - but in general, intellect doesn't help reproductive success enough to affect natural selection.
The Geographic describes Mr. Khan's technique:
Documents written during or just after Khan's reign say that after a conquest, looting, pillaging, and rape were the spoils of war for all soldiers, but that Khan got first pick of the beautiful women.
The Khan's strategy was a bit more subtle than that. His agents selected pretty women for him, but they favored women whose husbands had survived the battle. The Khan wasn't going to hang around and help raise his children, of course; focusing on women who already had men taking care of them enhanced his reproductive success.
Natural selection clearly favors women who can attract a man strongly enough to get him to help feed her children. The younger she is when she first attracts a man, the more babies she'll be able to have.
Natural selection favors men who are willing to take care of women but men can also achieve reproductive success by wandering around. Women figure this out pretty quickly and institute all kinds of customs and peer pressure to try to persuade men to stick around instead of wandering.
Natural selection favors women who like to share information about raising their children. And it selects men who don't talk much because talking scares away the animals while hunting.
Assuming that a woman has a long-term relationship with a man who's feeding her, her chance of reproductive success is as good as it's going to get, but what about passing on his genes? Helping her raise children helps him only if her children are his. Men who weren't jealous or who didn't watch their women carefully raised other men's children instead of their own and were bred out of the gene pool.
Natural selection favors women who can persuade men to feed them, and it favors men who are extremely possessive of the women they feed.
That's basic natural selection, but there are variations. A woman benefits from nourishing and maintaining a long-term relationship with her meal ticket. Assuming she can get away with it, however, natural selection favors having children by other men.
Suppose she's not particularly attractive and ends up with a man who's not particularly strong. She's better off if she can get pregnant by someone stronger than her husband. Her husband's reproductive success improves if he's jealous, possessive, and keeps other men away from her. In many primitive societies, it's OK for a man to kill his wife and her lover if he catches them in the act.
Jealousy makes a man want to possess his woman. It also forces him to stick around to keep an eye on her so that other men can't get to her.
It's to her advantage if he can't tell when she's fertile while he's guarding her. Human females are fertile for only a few hours per month, maybe a day at most. If her husband knows when she's fertile, he can watch her then and spend the rest of the month chasing other women.
Her reproductive success improves if he sticks around to feed her every day, however, so she's better off if he can't tell when she's fertile. Having sex with him when she's not fertile wastes his reproductive potential, of course, and it probably bores her because she's not really interested, but having sex often benefits her by giving him a reason to stick around and help her instead of chasing someone else.
Natural selection 101 is for a woman to find a man to take care of her and for a man to take care of a woman but for her to get pregnant by someone stronger and for him get other women pregnant while keeping other men away from her. He'll have to be jealous and possessive or he'll raise other men's children and be out of the gene pool, she'll be jealous because she doesn't want him limiting her reproductive success by giving other women food her children could eat.
Natural selection emphasizes possessiveness in both women and in men and it favors extracurricular activities in both women and in men. How gender-neutral can you get?
There is one major difference - men who talk while hunting won't catch anything so men learn not to talk. They learn to hunt by watching older hunters and to farm by watching others farm. Farming involves a great many back-breaking tasks such as plowing, weeding, and harvesting which leave men too short of breath to talk much.
Women who talk while raising children have more reproductive success because sharing information helps keep their babies alive. Natural selection favors women who yearn to talk and men who'd rather not talk. This causes problems for women because they tend to measure the strength of the relationship by the amount and quality of the talk just as men tend to measure the relationship by the amount and quality of the sex.
That's pretty much how natural selection has shaped men and women over the years. Women gain by getting men to feed them, men gain by feeding as many women as they can but they also gain by going after women who're fed by other men. This selects for jealousy in both men and in women but more strongly in men.
A woman whose husband feeds other women doesn't lose out in the game of reproduction so long as there's enough food for her and for her children, whereas a man whose wife gets pregnant by another man loses her reproductive potential for the year or two it takes for her to have the baby and nurse it long enough that she can become fertile again. That's one reason some men are violent to their girlfriend's children - helping her take care of another man's child benefits him not at all.
The next article in the series talks about how marriages worked in low-tech, muscle-powered, agricultural societies.