A few years back, evolutionary psychologist Daniel Kruger was wandering around Manhattan when a Time Out New York cover grabbed his eye — a Godzilla-sized woman in a red dress rampaging through the city streets next to the headline: "Attack of the Single Women!" Inside: an article about the plight of the unmarried women in a metro region where they outnumber potential male mates by three-quarters of a million (about a 10-to-9 ratio).
Kruger, a research professor at the University of Michigan's School of Public Health, wondered: "What if there really were a lot more single women than single men? What would that do to population dynamics, to male and female romantic relationships, to negotiating sexual relations and commitment?"
As it turns out, such an imbalance makes men in their 20s less likely to get married, but men in their 30s more likely to get hitched, at least as compared to in the regions where men slightly outnumber women. Kruger's findings are published in The Journal of Social, Evolutionary, and Cultural Psychology.
To understand why, one needs to know something about the often conflicting evolutionary motivations that drive male and female reproductive strategies, and how they change (particularly for men) over the course of a lifetime.
In young men, the selfish gene seeks to spread itself far and wide, mostly because it often can (and with minimal investment of resources) — hence, the rakish male tendency to love 'em and leave 'em. Women, on other hand, tend to be more discriminating. They're the ones who have to carry the baby around for nine months, then nurse it to independence. In women, the selfish gene prefers a mate with both the wherewithal and the resources to stick around and raise the kid.
Translation? "Men will be looking for short-term uncommitted relationships, women will be looking for relationship commitment," said Kruger. "These are the things that have driven evolution. ... Because of different interests, women offer a sexual relationship in exchange for commitment, and men offer commitment in exchange for sex." (In a separate study, Kruger surveyed undergraduates to learn that, indeed, females were much more likely to admit to having traded sex for "investment," while males were much more likely to have done the reverse)
But if reproduction is a kind of bargaining game, it means that when guys become scarcer they can drive a harder bargain. "The more women are around, the more opportunities there are for men, and the men can lower their offers for commitment and investment because they know they are likely to find another partner," said Kruger. "But women can't put their foot down and say 'marry me or else' because this guy has other alternatives."
On the other hand, in places where men outnumber women, young fellows who find a suitable gal are more likely to want to make sure they hold onto her. Hence, the higher marriage rates among 20-something men in cities where dudes abound.
Around age 30 or so, however, men start to become more interested in long-term relationships, and they switch from acting like cads to acting like dads. This is because, as their features soften and their testosterone levels fall, men lose their desirability as one-night-stand material, Kruger argues. The theory goes that if women are going to be loved and left, they want it to be with a virile young man. That way, at least the child will be genetically fit, even if the guy doesn't stick around. Older men, then, are left only with the good-provider card to play.
"So guys shift strategies," said Kruger. "But in female-biased populations, they still have the advantage of market scarcity." Meanwhile, in the male-biased populations, there are even fewer mates left for those who waited. Hence, the lower rates of marriage among 30-somethings in those populations.
Gender balances also have consequences for social norms, an argument that was originally put forth by Marcia Guttentag and Paul Secord in a 1983 book called Too Many Women? In times and places where men are scarce, competition among women leads them to be more forward in their seduction. Sexual mores grow looser. Historically, hem lines rise. But at the same time, not being tied down often gives women more freedom to pursue their careers and education, and develop their own independence.
Perhaps it's not a coincidence, suggests Kruger, that when women began to outnumber men in the United States after World War II, the cultural and feminist revolution of the 1960s soon followed.
On the other hand, in places and times when women are in shorter supply, men do their best to promote chastity and to treat women as the fairer sex to be cherished and protected.
Think Southern belles, said Kruger: "In the South, where you have had a heavily male-biased population [because of the agricultural economy] women were valued and adored for their physical beauty. They were put on a pedestal but also shackled to that pedestal. ... If guys didn't have control over women then you'd see polyandry — women having relationships with multiple guys. Guys keep social norms rigid because they are terrified of that happening."
Excess males in the population also tend to turn men more aggressive, generally, and make men more likely to engage in all kinds of risky behaviors that actually result in higher male mortality rates, mostly from accidents, homicides and suicides. "If you go to Alaska [male to female ratio of 107-to-100, highest of any U.S. state]," warned Kruger, "be on your guard. These guys are sensitive to threats to their relationship status."
Much worse than Alaska, however, is China, where the male-to-female ratio is now 120-to-100 and Chinese government has expressed concerns "about the consequences of large numbers of excess men for social stability and security." Kruger is worried too: "That is a real danger sign. Historically it's been associated with warfare with other groups. ... You can't have all these single guys who aren't getting any sexual satisfaction; it's a very volatile situation." (Historically, a shortage of women has often been followed by a period of conquest.)
On the other hand, when women outnumber men, said Kruger, "They do get depressed and go inward, though the adverse consequences are less likely to be violent. You won't see a marauding band of women streaming from Manhattan to invade the neighboring population." So much for the imaginative cover designers at Time Out New York.
To one New York City dating expert, however, there's more to the dating game than just the numbers. "Statistically, the research makes sense," said Arthur Malov, the head dating coach at New York Dating Coach. "But people are emotional, and so I think it doesn't take into consideration all the factors such as attractiveness, such as density and how many times women get approached."
Malov finds that in his experience, men are more than anything interested in a pretty face, whereas women are more likely to consider a larger package of attributes. So, as long the as long as a girl is cute, she can be choosy, too.
Women also benefit from the population density of a place like New York, says Malov, because there are just so many opportunities for them to get noticed. "If you live in small-or medium-sized town, everything is so spread out, and women do not get approached as much," said Malov. "And when a girl's not being approached all the time, it's actually easier for guys to meet women. I speak to guys all the time, and guys from other states complain it's harder to meet girls here than in the Midwest or the South."
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