The New York Times is running a fascinating story by Patricia Leigh Brown on children who act like, even want to be, the opposite sex. The story is mostly about the sad conflicts these children, and their parents, face.
Brown cites some of the very few scholars who have studied what happens to these children later. The results for boys and girls, in this as in many other kinds of sex difference, are strikingly different. In some studies, about a quarter of "gender variant" boys grow out of it, a majority become gay, and the remaining small fraction come to think of themselves as transgender, or something else. Most of the girls, on the other hand, grow out of it. Brown cites Dr. Kenneth Zucker, who has treated some 500 gender variant children at the Center for Addiction and Mental Health in Toronto, who said that about 80% of his patients grew out of it – though she does not report if he had different results with boys and girls.
The science of sexual identity is still pretty mysterious. I take these early studies as further confirmation, though, that males and females are different from one another in how much of their gender and sexual identity is nature, as opposed to nurture. Men seem more polarized – either one way or the other – and more shaped by their biology. Women seem to fall more along a spectrum, and where they fall on it seems to be more amenable to change over time.
As I have read the evidence thus far, I don't think I could say anything more definite than that. I believe, though, that the more we know about the science of sex-anything, the more we will see differences between males and females.