Zucker, both psychologists, published a seminal paper on childhood markers of homosexuality in 1995. Curiously enough, the age-old homophobic fears of many parents reflect some genuine predictive currency. In looking carefully at the childhoods of gay adults, researchers are finding an intriguing set of behavioral indicators that homosexuals seem to have in common. It is only relatively recently, however, that developmental scientists have conducted controlled studies to identify the earliest and most reliable signs of adult homosexuality. These behavioral patterns are feared, loathed and often spoken of directly as harbingers of adult homosexuality. In little girls, there is the outwardly boyish stance, perhaps a penchant for tools, a square-jawed readiness for physical tussles with boys, and an aversion to all the perfumed, delicate trappings of femininity.

We all know the stereotypes: an unusually light, delicate, effeminate air in a little boy's step, an interest in dolls, makeup, princesses and dresses, and a strong distaste for rough play with other boys.

Excerpted from Why Is the Penis Shaped Like That? … And Other Reflections on Being Human, by Jesse Bering, by arrangement with Scientific American/Farrar, Straus and Giroux, LLC (North America), Transworld Ltd (UK), Jorge Zahara Editora Ltda (Brazil).