Heritability is not about a person heritability is always about a population.

The current evidence really focuses on twin studies, and these studies suggest that the heritability of sexual orientation ranges between 30 and 40 percent. There was a lot of research in the '90s where people were hoping to find a genetic marker that didn't go too well. All geneticists know that no complex human behaviors are determined by single genes. Probably the strongest current evidence is for genetic contributions-but that doesn't mean we've found a gene. What do we actually know? How much of a person's sexual orientation can be chalked up to biology? This interview has been condensed and lightly edited.

She spoke with Newsweek about what she and her colleagues in the field know-and what they don't-about how a person's sexual orientation might form. Recently, scientists announced that they found some genes that might be associated with sexual orientation and a biological explanation for the reason gay men tend to have older brothers.īut the field of sexual orientation research is far broader and more complicated than two studies-and Lisa Diamond, a psychologist and sexual orientation researcher at the University of Utah, knows that better than most.