As it turns out, a man's ring finger can tell a lot about him.
The length of a man's fourth finger has been linked to sexual orientation, libido level, penis size, and even risk for certain diseases, according to The Daily Mail. Previously, ring finger length had been able to link to sperm count, aggressive behavior, sports prowess, while high levels of testosterone are associated with a higher sex drive.
A new study reported sex hormone exposure in the womb determines finger length. Published in this week's issue of Proceedings of the National Academy of Sciences, researchers studied digit length in mice, which are considered to have similar digit ratios as human males and females.
After exposing the mouse embryo to more male hormones, the mouse had a significantly longer fourth digit. More estrogen resulted in a smaller fourth digit. Almost all of the male mice in this group had genital defects.
Professor Martin Cohn and Dr. Zhengui Zheng, biologists at the University of Florida, say the fourth finger is packed with receptors for sex hormones.
Sex hormones affect finger length, and the ratio is fixed before the bone has even developed, Cohn said. This happens during a narrow window of development, but it stays fixed throughout life.