Length of a Man's Ring Finger Indicates Amount of Sex Hormones, According to Science

Finally, a pair of Gainesville biologists have discovered another reason for men having ring fingers longer than their index fingers, and as folklore would have it, it's related to sex.

The findings of the University of Florida College of Medicine developmental biologists, Martin Cohn and Zhengui Zheng, add to the long list of things that are said to be determined by the "digit ratio," specifically the "2D:4D" ratio -- which compares the ring and index fingers.

Now, in addition to penis size, athletic ability, and dozens of other traits thought to be indicated by this ratio, the Florida biologists are now adding sex drive to the list.

The researchers found through testing on mice embryos that with more androgen (testosterone) present in a system, the fourth digit is longer, while more estrogen indicates that finger will be shorter.

The male mice subjected to higher levels of estrogen not only lost some length on the fourth digit but it also created a more feminized look in the mice, according to the research.

"The discovery that growth of the developing digits is controlled directly by androgen and estrogen receptor activity confirms that finger proportions are a lifelong signature of our early hormonal milieu," Cohn told the University's news department. "In addition to understanding the basis of one of the more bizarre differences between the sexes, it's exciting to think that our fingers can tell us something about the signals that we were exposed to during a short period of our time in the womb."

Aside from all the sexual implications and the cultural references from the digit ratio, scientists actually think it'll help them understand immune system diseases and how certain cancers work.

In practical terms, you may want to start checking the ratios of men to see what they're all about.

The biologists' research is published in this week's Proceedings of the National Academy of Sciences.