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

for promiscuous behavior: in most species, females mate much more than is necessary to avoid sterility. Nor do I accept the popular notion that females who store sperm only remate because they’ve run out of it. To be sure, females can run out of sperm. In most species, though, they leap back into bed long before sperm depletion becomes a problem. And while I’m dismissing ideas, let me also put to rest the idea that females are promiscuous in order to increase the genetic diversity of their offspring. Genetic diversity is always a consequence of female promiscuity but rarely a cause.
    To get back to shiner perch, however, the theory that promiscuous females are hedging against male sterility is plausible. Shiner perch are unusual fish. Rather than shed eggs and sperm into the sea as so many fish do, they copulate, the male placing sperm packets into the female’s genital orifice. What’s more, the females don’t lay eggs—they actually give birth. But there’s a long delay—several months—between the time females mate and the time they fertilize their eggs. By then, males have lost interest in sex and their testes have shriveled for the winter. If a female had only one mate and he turned out to be sterile, she would lose out on breeding for the whole year. Surely you wouldn’t want that?
    You do, though, raise an interesting matter. If a proclivity for promiscuity is genetic, then yes, promiscuous behavior will become more common if loose females tend to have more children than their monogamous peers. That’s how natural selection works. Unfortunately, though, we don’t know much about the genes that influence female sexual behavior in any animal, let
alone in shiner perch. What I can say is that in both the fruit fly Drosophila melanogaster and the field cricket Gryllus integer, females do differ in their inclination to have fun, and this can largely be accounted for by genetic differences. So, boys, take a long look at your girlfriend’s mother—if she was a good-time girl, the odds are on that your girlfriend will be too.

    Dear Dr. Tatiana,
    Â 
    I’m consumed with existential angst. I’m a stalk-eyed fly, Cyrtodiopsis dalmanni, and every night girls line up to mate with me, but I rarely see the same girls twice. Worse, few of my visitors are virgins—and I know that they’ll go on to other guys night after night after night. What are they looking for, and why can’t I satisfy them?
    Â 
    Feeling Inadequate in Malaysia

    True, female stalk-eyed flies are massively promiscuous. But they have exacting taste. Females of your species are irresistibly drawn to a fellow with stalks so imperial that his eyes are set farther apart than his body is long. When dusk falls in the tropics, as you know from personal experience, stalk-eyed flies gather at streams, where they settle for the night on the fine root hairs that stick out under the banks. Females head for the root hairs presided over by the male with the longest stalks—and in the morning, they copulate with him before flying off for another day’s foraging.
    You see, girls may say they want a kind, sensitive, devoted guy—that personality matters more than looks—but the truth is, in many species, females are body fascists. That’s why as a rule
it’s the males that have ridiculously long tails or fancy headdresses—or eyes perched on the ends of long, stiff stalks.
    Darwin was perplexed by the extravagant ornaments and decorations that grace the features of so many males. The evolution of weapons was easy to explain. Not so ornaments. All too often, ornaments seem to work against natural selection by making it much harder to survive. The peacock’s tail might look superb—but have you ever seen peacocks fly? It’s a ludicrous sight. They lumber through the air, an easy snack for a tiger.
    To explain how huge tails and other frivolities could evolve despite