In Most Species, Faithfulness Is a Fantasy
You can accuse the disgraced ex-governor Eliot Spitzer of many things in his decision to flout the law by soliciting the services of a pricey prostitute: hypocrisy, egomania, sophomoric impulsiveness and self-indulgence, delusional ineptitude and boneheadedness. But one trait decidedly not on display in Mr. Spitzer’s splashy act of whole-life catabolism was originality.
It’s all been done before, every snickering bit of it, and not just by powerful “risk-taking” alpha men who may or may not be enriched for the hormone testosterone. It’s been done by many other creatures, tens of thousands of other species, by male and female representatives of every taxonomic twig on the great tree of life. Sexual promiscuity is rampant throughout nature, and true faithfulness a fond fantasy. Oh, there are plenty of animals in which males and females team up to raise young, as we do, that form “pair bonds” of impressive endurance and apparent mutual affection, spending hours reaffirming their partnership by snuggling together like prairie voles or singing hooty, doo-wop love songs like gibbons, or dancing goofily like blue-footed boobies.
Yet as biologists have discovered through the application of DNA paternity tests to the offspring of these bonded pairs, social monogamy is very rarely accompanied by sexual, or genetic, monogamy. Assay the kids in a given brood, whether of birds, voles, lesser apes, foxes or any other pair-bonding species, and anywhere from 10 to 70 percent will prove to have been sired by somebody other than the resident male.
As David P. Barash, a professor of psychology at the University of Washington in Seattle, put it with Cole Porter flair: Infants have their infancy; adults, adultery. Dr. Barash, who wrote “The Myth of Monogamy” with his psychiatrist-wife, Judith Eve Lipton, cited a scene from the movie “Heartburn” in which a Nora Ephronesque character complains to her father about her husband’s philanderings and the father quips that if she’d wanted fidelity, she should have married a swan. Fat lot of good that would have done her, Dr. Barash said: we now know that swans can cheat, too. Instead, the heroine might have considered union with Diplozoon paradoxum, a flatworm that lives in gills of freshwater fish. “Males and females meet each other as adolescents, and their bodies literally fuse together, whereupon they remain faithful until death,” Dr. Barash said. “That’s the only species I know of in which there seems to be 100 percent monogamy.” And where the only hearts burned belong to the unlucky host fish.
Even the “oldest profession” that figured so prominently in Mr. Spitzer’s demise is old news. Nonhuman beings have been shown to pay for sex, too. Reporting in the journal Animal Behaviour, researchers from Adam Mickiewicz University and the University of South Bohemia described transactions among great grey shrikes, elegant raptorlike birds with silver capes, white bellies and black tails that, like 90 percent of bird species, form pair bonds to breed. A male shrike provisions his mate with so-called nuptial gifts: rodents, lizards, small birds or large insects that he impales on sticks. But when the male shrike hankers after extracurricular sex, he will offer a would-be mistress an even bigger kebab than the ones he gives to his wife — for the richer the offering, the researchers found, the greater the chance that the female will agree to a fly-by-night fling.
In another recent report from the lubricious annals of Animal Behaviour entitled “Payment for sex in a macaque mating market,” Michael D. Gumert of Hiram College described his two-year study of a group of longtailed macaques that live near the Rimba ecotourist lodge in the Tanjung Puting National Park of Indonesia. Dr. Gumert determined that male macaques pay for sex with that all-important, multipurpose primate currency, grooming. He saw that, whereas females groomed males and other females for social and political reasons — to affirm a friendship or make nice to a dominant — and mothers groomed their young to soothe and clean them, when an adult male spent time picking parasites from an adult female’s hide, he expected compensation in the form of copulation, or at the very least a close genital inspection. About 89 percent of the male-grooming-female episodes observed, Dr. Gumert said in an interview from Singapore, where he is on the faculty of Nanyang Technological University, “were directed toward sexually active females” with whom the males had a chance of mating.
Significantly, males adjust their grooming behavior in a distinctly economic fashion, paying a higher or lower price depending on the availability and quality of the merchandise and competition from other buyers. “What led me to think of grooming as a form of payment was seeing how it changed across different market conditions,” Dr. Gumert said. “When there were fewer females around, the male would groom longer, and when there were lots of females, the grooming times went down.” Males also groomed females of high rank considerably longer than they did low-status females with nary a diamond to their page.
Commonplace though adultery may be, and as avidly as animals engage in it when given the opportunity, nobody seems to approve of it in others, and humans are hardly the only species that will rise up in outrage against wantonness real or perceived. Most female baboons have lost half an ear here, a swatch of pelt there, to the jealous fury of their much larger and toothier mates. Among scarab beetles, males and females generally pair up to start a family, jointly gathering dung and rolling and patting it into the rich brood balls in which the female deposits her fertilized eggs. The male may on occasion try to attract an extra female or two — but he does so at his peril. In one experiment with postmatrimonial scarabs, the female beetle was kept tethered in the vicinity of her mate, who quickly seized the opportunity to pheromonally broadcast for fresh faces. Upon being released from bondage, the female dashed over and knocked the male flat on his back. “She’d roll him right into the ball of dung,” Dr. Barash said, “which seemed altogether appropriate.”
In the case of the territorial red-backed salamander, males and females alike are inclined to zealous partner policing and will punish partners they believe to have strayed: with threat displays, mouth nips and throat bites, and most coldblooded of all, a withdrawal of affection, a refusal to engage. Be warned, you big lounge lizard: it could happen to you.
Copyright 2008 The New York Times