Perhaps the biggest splash was made in 1993 by Dean Hamer’s team at the National Cancer Institute in Bethesda, Maryland, when they found that gay brothers tended to share a sequence of five genetic markers in a region of the X chromosome. Over the last two decades, several studies have suggested that sexual orientation is, in part, down to our genes. “The predictive test needs replication on larger samples in order to know how good it is, but in theory it’s quite interesting.”
“The scientific benefit to understanding is obvious to anyone with an iota of curiosity,” says Michael Bailey at Northwestern University in Evanston, Illinois.
