• Choose a category
• All
• Classic-Fiction

So a certain amount of homosexual behavior isn't any more of a mistake in the beetles than any other trade-off between two traits might be. Instead, that very flexibility in mating behavior, where decisions are made based on shifting criteria that may be apparent only at the last moment, might itself be favored by natural selection. It allows animals to be opportunistic in their behavior, and increases their ability to roll with the punches of a changing environment.

Mistaken identity, however, doesn't seem to be what's going on in a tiny fly that lives on the water lilies of English streams. Males wander on the surface of the leaves, pouncing on anything that remotely resembles a female and a few things that do not, such as gray specks of decay on the plants, or flies of other species. After he succeeds in mounting a female, the pair embarks on an elaborate courtship ritual in which they rock back and forth for up to 15 minutes. An uncooperative female quickly puts a stop to this activity, in which case the male leaves without bothering her further. Sometimes, however, a male mounts another male, and in these cases the mounted individual vigorously resists the overtures while the mounting male clings to his back as if to a tiny bucking bronco. Ken Preston-Mafham, who has studied the flies in War-wickshire, believes that the mounting male is preventing his partner from getting to the females that will light upon the lily leaf. If males are competing for access to the females, a male that simply rides another individual is in the best position to leap off his rival and seize the female himself.

Finally, there may be some unforeseen advantages to homo sexual behavior, regardless of why and how it arose. As I mentioned, flour beetles, the tiny pests infesting your kitchen cabinets, are useful models for genetic and other biological research. Like the other insects I just described, male flour beetles will mate with other males. Work in Sara Lewis's laboratory at Tufts University in Massachusetts showed that when one of the males mated with a female right after such a homosexual interaction, on a few occasions enough sperm from the other male was left that it actually fertilized some of the female's eggs. Although this is unlikely to be a frequent occurrence, it suggests that some reproductive benefit could partially offset any wasted time or effort in the male-male interactions.

Flies with Designer Gay Genes

WEIRD sexual proclivities of bedbugs aside, what people really want to know is whether homosexuality has a genetic basis. Because it is much easier to search for such genes using quick-breeding study animals, the fruit fly Drosophila has become the poster insect for studies of sexual orientation genetics, as it has for so many other traits. Although people rarely identify with insects, particularly tiny buzzy ones such as flies, in this case the media has reliably been all over any new finding that deals with homosexuality in Drosophila, with headlines such as "Fruitflies Tap in to Their Gay Side," "Gay Drunk Fruit Flies," and even "Gay Fruit Fly for President" (not sure what that was about, frankly). Google "gay fruit flies" and you get upward of 270,000 hits.

Scientists were not looking for homosexual flies when they began this research. Indeed, most if not all of the researchers whose papers end up providing fodder for headlines like those above would not describe themselves as studying sexual orientation at all. Instead, they are trying to understand how the brain sends and receives signals from the sense organs, or attempting to break down the processes of courtship and mating into their most fundamental components. What exactly has to happen for boy to meet girl so that baby can make three (or thirty, or maybe three hundred, in the case of the flies)?

It turns out that sex, even for such relatively simple animals, requires a sophisticated orchestration of steps. Although different species of Drosophila do things somewhat differently, in many fruit flies the females must