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Beware of Seducers Bearing Gifts

Posted by Richard Conniff on November 22, 2011

Some male spiders deceive the females they mean to seduce with wedding gifts that look good but don’t offer much beyond the wrapping, according to a new paper just out in BMC Evolutionary Biology.  I wrote about the delicate negotiating of gifts between male and female in my book The Natural History of the Rich.  I also did an NPR commentary on the topic a few years ago.

But beware, reader, I am trying to seduce you with a gift:

When evolutionary psychologists talk about human sexual behavior, they tend to draw analogies from the animal world and they particularly like to talk about hangingflies.  These inch-long predators live by the thousands in the temperate forests of North America.  They specialize in catching other insects, injecting digestive enzymes into them, and sucking out their innards.  So the analogy to the behavior of rich people may seem remote.  But when a male hangingfly wants romance, he goes out and catches an even bigger insect than usual and advertises his catch to the female world.   Male and female pair off in the undergrowth, hanging by their forelimbs face-to-face like trapeze artists about to attempt an aerial minuet.  (One can imagine the billionaire balloonist Richard Branson in this position, all banked blond hair and eager teeth.)  He clutches the dead insect in his hind legs and holds it up to her as a nuptial gift–or to put it in human terms, he buys her dinner and she allows sex to follow.

But neither male nor female is a patsy in this partnership.  If the dinner is too small, she throws him out before he can do much good.  It’s a variation on the “diamonds are a girl’s best friend” theme, and bigger diamonds, or dead insects, make better friends.  It takes twenty minutes of vigorous copulation to get her to lose interest in other males and lay her eggs–and he only gets twenty minutes if he brings her a big gift.  On the other hand, when his twenty minutes are up, the male may grab back his nuptial gift and fly away with it to seduce other females.

Does this begin to sound terribly familiar?  You are probably already thinking of offensive analogies.  For instance, when Donald Trump’s prenuptial agreement offered second wife Marla a piece of the real money after five years of marriage, and he then dumped her in year four, was he not managing his reproductive assets in a manner and with a timeliness worthy of a hangingfly?

The leap from hangingflies to humans is of course perilous.  In our species, both males and females typically consider the resources a potential long-term mate can bring to the relationship.  Upper class men of past generations weren’t merely seeking good bloodlines when they did their dating mainly out of the pages of The Social Register or Debrett’s, nor when they asked one another that odd question, “What does her father do?”  “I won’t say my previous husbands thought only of my money,” the Woolworth department store heiress Barbara Hutton once remarked, “but it had a certain fascination for them.”  And yet in study after study, human females demonstrate a far more pronounced inclination to seek a partner with resources.  Contrary to feminist expectations, women with good prospects of their own tend to place even greater emphasis on a man’s financial status.  Or as a Dallas commercial real estate saleswoman put it, commenting on rich men in general:  “They have a little caption over their head that says, ‘Let’s go!’”  Feminists believe the urge to “marry up” the social ladder is cultural, a byproduct of economic discrimination and the blighted sensibilities of commercial real estate saleswomen.  Evolutionary psychologists say it’s also biological:  Women make a huge parental investment in their offspring, so in our evolutionary past there was a significant survival advantage in finding a helpmate who could provide compensatory effort and resources.

The evidence for the parental investment argument in other species is strong.  Where females bear most of the cost of rearing offspring, they are exceedingly scrupulous about choosing males who demonstrate greater fitness or, like the hangingfly, provide valuable resources.  Insisting that the male put some food on her plate isn’t the animal equivalent of prostitution, a simple quid pro quo food-for-sex exchange.  It’s a way for the female to get the energy she needs to reproduce, and also a way to judge the merits of a prospective mate.  In common terns, for instance, courtship feeding of his mate is a reliable indicator of a male’s subsequent parental feeding of their young.

In humans, biology puts the cost of reproduction almost entirely on females.  The father’s contribution equals the mother’s in just one regard, which happens to be the payoff:  He provides half the child’s genome.  Otherwise, the disparity in effort is appalling.  A woman produces just 400 eggs in a lifetime, a man four trillion individual sperm, which works out to about 125 million a day, or to carry this to a ridiculous extreme, which is after all the male way, a little more than 86,805 potential human beings a minute.  This means that his opportunity cost–what he gives up in choosing one mate over another–is almost nil.  And her cost is almost infinite.  On top of that, the woman must then invest 80,000 calories in her pregnancy, roughly the energy it would take her to run from New York to Chicago, plus another 182,000 calories to nurse the baby for a year, almost enough energy to plug onward to San Francisco.  Or bust.  Meanwhile, the male’s direct contribution from his single intrepid sperm is about .000000007 of one calorie, or not quite enough energy to roll over in bed and fart loudly.  Is it therefore any wonder that women like men who demonstrate an ability to help out?  Or that somewhere in our benighted past, male earning power became a useful gauge of reproductive potential, much as men still gauge female reproductive potential primarily on the basis of pretty faces, or nice money-makers, well-shaken?



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