Sex on Six Legs_ Lessons on Life, Love, and Language From the Insect World - Marlene Zuk [66]
Taking a Pill?
SO WHAT does the research from insects tell us about homosexuality? All of the scientists using genetic alterations in Drosophila hasten to point out that despite the flies sharing 75 percent of human disease genes, no counterpart to fruitless exists in people. So even though what the flies are doing looks at least somewhat like what humans do, the insects got to a similar destination through vastly different modes of transportation on different highways.
It is certainly true that the attraction to members of one's own sex is common in nature among many species, and its sources can be traced in the lab, at least for the flies. If that resonates with your world view on homosexuality, whether to accept or eschew it, so be it. But homosexual behavior means something different to the flies than it does to more complex and more social animals, such as the primates, birds, and other vertebrates that exhibit same-sex behavior. For example, Laysan albatross in Hawaii form female-female pairs that stay together for many breeding seasons, rearing chicks together if one or both of them has been inseminated by a male in the colony. Bonobos, smaller relatives of the chimpanzee, frequently exhibit sexual behavior between males or between females; sex seems to be used in bonobo society as a way to resolve social tension in the group. In these and many other animals, sexual behavior is about more than reproduction. People unfamiliar with life in the wild often envision animals keeping their sexual contact to a businesslike procreative minimum, where male and female meet, mate, and part as soon as the plumbing has everything lined up. But in social animals, sex is not just reproduction—it is communication, part of a continuum of dealing with other members of your species.
Fruit flies and the other insects I have been discussing do not have elaborate social systems in which such subtleties are important. Yet they still exhibit same-sex courtship and even mating. The conclusion, though, is not that bugs are stupid, but that sex is hard. Figuring out how to do it involves a complex interplay between genes and the environment. Featherstone and many of the other researchers using genetically modified flies measure their behavior by observing how the mutants respond, not to a living, breathing companion, but to a male or female with its head cut off. The fly's body still emits the same odor cues and provides the same audience for the displays, but it obviously cannot interact with its partner. The decapitation controls for the inevitable interaction between individuals that could alter the results. The genes don't just issue commands that make the flies behave in a certain zombielike way regardless of circumstances. Instead, the genes, and the chemicals they deploy, affect the way that experiences such as being rejected or accepted by another fly are interpreted.
The flies and other insects may also use some of the same-sex interactions as a way to practice their technique. Young male Drosophila are often courted by older ones, and Scott McRobert and Laurie Tompkins showed that males that had been the recipient of such courtship in the lab were more successful in wooing females later in life. The difference was not huge, but in evolution, every little bit counts. In a different species of Drosophila than the one used for most of the genetic research described above, males that are isolated from other flies during development have a hard time telling their own species from similar ones, a crucial skill, since hybrid offspring are not fertile and, hence, an evolutionary disaster. It takes experience with one to know one, it seems, even though Drosophila lack a true social organization like that of wolves, bonobos, or