That hasn't happened yet. But the clear focus of sexual-orientation research has shifted to biological causes, and there hasn't been much science produced to support the old theories tying homosexuality to upbringing. Freud may have been seeing the effect rather than the cause, since a father faced with a very feminine son might well become more distant or hostile, leading the boy's mother to become more protective. In recent years, researchers who suspect that homosexuality is inborn - whether because of genetics or events happening in the womb - have looked everywhere for clues: Prenatal hormones. Birth order. Finger length. Fingerprints. Stress. Sweat. Eye blinks. Spatial relations. Hearing. Handedness. Even "gay" sheep.
These studies have been small and underfunded, and the results have often been modest. Still, because there's been so much of this disparate research, "all sort of pointing in the same direction, makes it pretty clear there are biological processes significantly influencing sexual orientation," says LeVay. "But it's also kind of frustrating that it's still a bunch of hints, that nothing is really as crystal clear as you would like."