Digit ratio predicts penis length

In addition to its relationship to a variety of diseases, the length ratio of the second and fourth fingers also correlates with stretched penile length in men.

Jul 5, 2011
Jef Akst

FLICKR, JON GENIUS

You know the old wives tale about the size of a man's feet? Well, science has uncovered evidence that his hands may hold a similar predictive power. According to a study published online yesterday (July 4) in the Asian Journal of Andrology, the length of a man’s fingers is indicative of his stretched penile length—the shorter the second finger is relative to the fourth, the longer the penis. The 2D:4D ratio of the male hand has previously been linked to a variety of biological characteristics, including general attractiveness and the risk of developing certain diseases such as prostate cancer. These correlations are likely due to differences in prenatal testosterone levels and the sensitivity of the androgen receptor, both key factors in penis development. The authors propose that higher prenatal androgen causes both the lower digit ratio and the longer penile length.

The finding adds to a growing body of literature that suggests that digit ratio may serve as a valuable biomarker for clinical conditions related to the effects of androgens during development, Denise Brooks McQuade of Skidmore College in Saratoga Springs, NY, wrote in an accompanying commentary.