Dr. Tatiana's Sex Advice to All Creation (12 page)

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Authors: Olivia Judson

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Consider two examples. The first comes from sharks. In these monsters, sex is often brutal. The male grabs the female in his jaws while attempting to insert one of his penises, or “claspers,” which are pelvic fins rolled into tubes. (Males have two claspers. They lie parallel to his belly, one end touching his genital opening, the other poised to insert into the female. During copulation, sperm from the genital opening enter a clasper and are propelled into the female with a jet of seawater.) Grown-up females are often scarred or missing bits of fin. However, although I wouldn't want to be bitten by a shark—even one in a tender mood—if you're a girl shark, it's not that bad. Take the blue shark. Mature females often have fresh bites or scars on their bodies. But they can handle it: when females go through puberty, their skin starts to thicken up; by the time they are adults, they have skin twice as thick as that of a male of the same size—and more telling, their skin is thicker than his teeth are long. In the round stingray, a cousin of sharks, not only does the female have thicker skin, the male has special pointy teeth to hold her with. Whereas females and young males have an array of smooth teeth that fit together like the stones on a well-paved street, a mature male has spiky teeth to give his love bites more oomph. And sometimes it's the female who bites the male—and the male who has evolved to reduce the risk.
Falcatus falcatus
is a shark known only from fossils that are about
320
million years old. The male would be laughed out of the water by today's sharks: on his head he was adorned with a large handle, a modified fin that curved forward over his head, giving him the appearance of a shark-shaped flatiron. Judging by the compromising position in which one fossil couple was found, it looks as if the handle evolved for the female to bite during sex.
My second example of the evolution of countermeasures comes from the marine flatworm
Pseudoceros bifurcus,
a hermaphrodite.
Among hermaphrodites, every member of the species is a potential mate; conventional fighting between rivals competing for mates does not exist. Indeed, for many hermaphrodites, sex is an amorous, drawn-out affair. But not for
Pseudoceros bifurcus.
In this species, individuals apparently prefer the male role over the female role, for they have evolved a technique of hit-and-run insemination. This involves stabbing the penis anywhere into the victim's body before gliding off with all possible speed. But since being stabbed in this way inflicts a gaping wound, any individual who can defend itself gains an immediate advantage. The result? Penis fencing.
As in all fencing, combatants try to hit without being hit; fighting is not to the death but to penetration. Duels can last for an hour, with each contestant striking and lunging, ducking and riposting. It's quite a sight. The creatures look like tiny Persian rugs—flat (obviously) and adorned with intricate and colorful repeating patterns. When they swim, they look like flying carpets. When they fence they look like invisible men dueling under long capes. A duel ends when one animal succeeds in stabbing the other with its penis. This is still not pleasant, but at least the loser put up a fight.
I hope I've convinced you that a bit of slap and tickle isn't necessarily sinister. Indeed, to come back to your case, male seaweed flies gather important information during mating tussles. Discriminating males do not mate with every female they overpower. Instead, they mate only with the most vigorous. The reason, it turns out, is that the most vigorous females are those who are most able to survive. No one knows why the males are so fussy. But one possible reason is that seaweed—which is where females lay eggs—appears on beaches unpredictably. Therefore, the more robust females should have a better chance of living long enough
to see seaweed arrive with the tide. So don't be shy. Get in there and beat the girls into submission.
Dear Dr. Tatiana,
 
I'm a sagebrush cricket, and I've just molted into manhood. While checking out my new manly body, I noticed some teeth on my back. This strikes me as a funny place to have teeth. What are they for?
 
Don't Know Much about Anatomy in the Rockies
Have you heard of a gin trap? It's a trap with spring-loaded jaws held open in a big toothy grin. When an animal steps on the trigger the jaws slam shut, the teeth seizing the quarry so it has no hope of wriggling free. Trappers once used gin traps to catch bears, wolves, mink, sable, and the like. In eighteenth-century Britain, these traps were even used to catch men. I'm not joking: giant steel gin traps were erected to catch poachers bent on filching game from the estates of aristocratic gentlemen.
Nowadays, happily, gin traps for mink and man alike are largely outlawed. But Mother Nature pays no attention to such niceties. The teeth on your back are a gin trap for catching girls. Here's how it works. In your species, it's traditional for the girl to be on top. When you curve your back upward to link genitalia, the flexion of your back causes the teeth of the gin trap to close on her belly, holding her fast. Once caught, she has to have sex with you whether she wants to or not. That's right. The gin trap enables you to rape her.
Why would you do that? Well, it's an ugly world. Female
sagebrush crickets have a wicked habit of their own: they drink your blood. You've probably noticed that as well as the gin trap, you have another odd bit of anatomy, a pair of soft, fleshy hind wings. You wouldn't get far if you tried to fly with them. No, I'm afraid they seem to have evolved for females to nibble. During sex, she takes a bite or two from your wings, then laps up the blood that oozes forth. Afterward, the blood dries and your hind wings become weird mutilated sculptures. Females naturally prefer virgins because only virgins are intact; after all, who wants someone else's chewed goods? But such picky behavior creates a problem for you males, who are naturally keen to mate more than once. That's why when a female climbs on your back to check the state of your hind wings, you grab her with the trap. If you're a virgin, it doesn't make a difference—she'd have sex with you anyway. But if your hind wings have been chomped, it's the gin trap that makes her stay.
Don't worry, you're not alone in having a device to seize unwilling girls. Look at scorpionflies, insects with long, clear gossamer wings splotched with black. Male scorpionflies have a “notal organ,” a clamp on their abdomen that they use to hold females down. As in your case, the notal organ is used in all matings; but again, it only becomes a weapon when a male is trying to hold a female against her will. What determines a female's willingness? Whether or not the male can provide a good meal.
Scorpionflies have an old-fashioned mating system: he pays for supper, she puts out. Because scorpionflies are among the vultures of the insect world—they are scavengers, feeding on insect carrion—a classy male will serve up a nice dead insect. Females readily copulate with males who can offer such a gourmet meal, but dead insects are often scarce. To get one a male may have to resort to stealing from a spider—a dangerous occupation. (Tip: If you're a boy scorpionfly, you'll have a big, bulbous penis. If you're
in a spider's larder and the owner tries to stop you, whack her with your member and she'll back off. Girls, if you ever find yourselves in the same predicament, your best bet is to head butt the poor spider.)
If a male cannot obtain an insect by means fair or foul, he uses his salivary glands to secrete a large gelatinous lump—yummy. Not as yummy as an insect but not bad. Some males, however, are not up to secreting the lump and don't fancy burgling a spider. Consequently, they have nothing to offer females and resort to force.
In both sagebrush crickets and scorpionflies, rape is the work of the ultimate loser, the fellow on the edge of society who can spread his genes in no other way. You see, in these species, it's better to make love to a willing female than to a furious, struggling, resisting one—males with willing partners copulate for longer, transfer more sperm, and sire more children. But if you're a male with nothing to offer, you won't be able to seduce anyone—and coercion is your only option. Indeed, natural selection discriminates against well-behaved losers. If you've nothing to offer and you don't resort to force, you won't have any children and your well-behaved genes will perish when you do.
But you shouldn't think that all rapists are desperadoes, guys who can't get a girl any other way. Rape has also been reported in lobsters, fish, turtles, birds, bats, and primates. The identity of the perpetrators is not always known: in the little brown bat, anonymous males creep through the vast winter roosts, raping females (and even males) who are hibernating. But among birds at least, rapists are typically respectable married men. Take the white-fronted bee-eater, a small, colorful bird that lives in big colonies throughout central and east Africa. Males and females form stable couples, nesting together year after year. But don't let that fool you. White-fronted bee-eaters are hardly living some
matrimonial idyll. Rape is commonplace. If a female ventures from her nest alone, she will probably be chased by at least one male and perhaps as many as twelve; if they succeed in pinning her to the ground, they all jump on her at once and try to mate with her. In some colonies, females have a one in five chance of being raped in a given year. Yet despite the fact that in a given year many males are bachelors—and under the desperado theory would be the chief suspects—the bachelors are innocent. Almost all would-be rapists are paired with other females in the colony. The lesser snow goose, another bird who lives in colonies, is even worse. In this species, married males routinely attack nesting females. A female left alone for an instant will probably be assaulted by the guy from the nest next door; the usual reason she's on her own is that her husband is off trying to rape someone else. In some colonies, each female is the victim of a rape attempt about once every five days.
As far as anyone can tell, however, this dreadful behavior rarely results in conception. The best estimates suggest that only 1 percent of white-fronted bee-eater chicks are conceived through rape; for the lesser snow goose, that figure is 5 percent. So why aren't these fellows content to look after their wives and children like upstanding members of the community? As in most other birds where males sexually assault females, everyone lives in close proximity. Under these circumstances a male doesn't have to look far for his victims: the cost of attempting rape is minimal. Therefore, the reward—in terms of additional children—needn' t be enormous for the behavior to persist.
But how do we know the girls aren't actually asking for it? Sexual coercion is always hard to judge: struggling is not necessarily an indication of reluctance. Many females, though, struggle only when their reluctance is real. Take the American lobster.
Females can mate after they've just molted as well as when their shells are hard. Females about to molt start visiting males, and when they find a fellow they like, they move in with him. No struggling there. Likewise, when a hard-shelled female wants to frolic, she'll present her rear to a fellow after the briefest of preliminaries. But an unwilling female will run from a male's advances. He'll give chase and may even try to haul her from her burrow. Or take scorpionflies. Females fly toward males bearing food and mate while they eat; they fly from empty-handed males. If captured, they fight vigorously to escape, twisting and turning their abdomens to avoid genital contact. When a female bee-eater mates with her husband—as she does once every couple of hours while she's laying eggs—she permits him to feed her an insect, then lifts her tail and holds still while he flutters behind her. But when she's accosted by other males, she flees. If they force her down, she presses her rear firmly against the ground and keeps her tail down, a posture that hinders sex. Moreover, before she leaves her nest, she whistles. If her husband is near, the whistle calls him over so he can escort her. It's a good idea: escorted females are hardly ever assaulted.
All this, together with the small fraction of rape attempts that produce offspring, suggests that resistance is not a ruse to attract male attention. Instead of lying back and thinking of England, most females adopt a “death before dishonor” response to sexual assault. Which raises another important question. Since resistance can result in serious injury or death, why don't females evolve to submit? This is not something that has been studied. But my bet is that there will often be a cost to submitting—one that, on average, outweighs the risk of injury or death. Such a cost can be inferred: remember that in some birds a male who suspects his mate of infidelity will make less effort to feed the
chicks, and chicks sometimes starve as a result. In some species of scorpionfly, females live off male efforts to provide food and never have to soil their hands by foraging, an activity that would increase their risk of becoming spider fodder. A female who fails to resist rape attempts would have to forage for herself or go hungry. And we know that in some species females suffer significant costs if mates are foisted on them—by a scientist, for example—rather than being chosen freely. In both the fruit fly
Drosophila melanogaster
and the field cricket
Gryllus bimaculatus,
females assigned a partner have fewer children than those who get to choose.
If male birds, lobsters, scorpionflies, and sagebrush crickets can gain from forcing females to have sex, what about humans? I know. The thought that rape could be natural—by which I mean an intrinsic, evolved part of a man's behavior—is distasteful, even offensive. But to be blunt, it is possible. Evolution does not obey human notions of morality, nor is human morality a reflection of some natural law. The deadly sins would be different if they mirrored evolutionary no-no's. Lust, for one, would be deemed a virtue; chastity would be deplored. In principle, rape could have evolved in humans just as in any other animal: if rapists, on average, had more children than other men, any genes underlying the behavior would spread.

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