In-utero testosterone influences finger length ratios and sexual orientation independently of postnatal hormone levels.

“Testosterone exposure in the womb creates a male vs female difference in finger length ratios that is also reflected in peoples reported sexual orientation.”

“Homosexual men show a “hyper male” pattern.”

“Exposure to testosterone in utero biases later sexual orientation.”

“As you'll learn today, the amount of testosterone that a fetus is exposed to while in the mother has a profound impact not only on the ratio of finger lengths, yes, you heard that right, but it also plays a meaningful role in sexual orientation.”