Read Online Dr. Tatiana's Sex Advice to All Creation by Olivia Judson - Free Book Online

get a microscope to the scene of the action. That means we can only draw inferences about sperm selection. Just because one male succeeds in fertilizing more of a female’s eggs than another doesn’t mean
the sperm have been expressly chosen. The successful sperm may be more competitive or more compatible. Or the effect may be due to chance. In the mallard, for example, females who have been artificially inseminated with a mixture of sperm from several males tend to use the sperm of one male for a given clutch. Which male is the lucky one changes each time, however, even though the female receives the same mixture of sperm—suggesting that the effect is due to sperm clumping rather than to an active preference for the sperm of one male in particular.
    As for yellow dung flies, claims have been made that the female’s decision to use one male’s sperm rather than another’s depends on whether she lays her eggs on a cowpat in the shade or one in the sun. It is a fascinating idea but extraordinary claims require extraordinary evidence, which we do not currently have. In any event, if I were you I’d concentrate on eliminating the option of your mate’s choosing sperm. If a male yellow dung fly copulates for long enough, he can displace the sperm of previous males (to achieve this effect, small males have to copulate for longer than big males, because small males transfer sperm more slowly). Having replaced the sperm of your predecessors with your own, you should then guard the female until she has laid her eggs. That way, you won’t have to worry: your sperm will be the only ones available. Go for it!
    So you see, there are lots of reasons females might play the field, although we don’t necessarily know the reasons in any given instance. Just in case you meet a girl on the prowl and you want to understand her motives, here’s a checklist of possibilities:
    She has run out of sperm
    Her other lovers were sterile

    Her other lovers had lousy genes
    Her other lovers had incompatible genes
    Her other lovers were ugly
    She wants diversity in her children
    She wants you for your food
    She wants help raising her kids
    She wants to enter your sperm in a competition
    She wants to give herself or her eggs a selection of sperm to choose from
    She wants to confuse everyone about who’s the father
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    You’ll notice that one obvious possibility is missing from the list—namely, that females sleep around for pleasure. The omission is deliberate: we know next to nothing about the evolution of sexual pleasure. I’d bet, though, that sexual pleasure is most likely to evolve when females have a lot to gain from promiscuous behavior.
    Folks, it’s time to bury forever the notion that female promiscuity is an unfortunate accident—a “malfunction,” the result of coercion, or simply a last resort to get a pesky guy to go away (known as “convenience polyandry,” this notion presumes that a male will stop harassing a female once he’s had his way with her). Which is not to say that females are never coerced or harassed into having sex. Or that sleeping around is always good. In the wasp Macrocentrus ancylivorus, for example, a female who mates too often gets clogged up with sperm and can’t fertilize her eggs. But like it or not, in countless species—from grasshoppers to fruit flies, pseudoscorpions to spiders, red-winged blackbirds to prairie dogs—it is not simply that females mate with lots of males. It’s that doing so is good for them: promiscuous females have more and healthier children. Natural selection, it seems, often smiles on strumpets. Sorry, boys.

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    SWORDS OR PISTOLS

    T he art of dueling is knowing when to fight, when to flee—and when to play dirty.

    Dear Dr. Tatiana,
    Â 
    I’m a fig wasps, and I’m in a panic. All the males I know are psychos. Instead of wooing us girls, they bite each other in half. What can