Selective breeding for a behavioral trait changes digit ratio.
The ratio of the length of the second priya gongura pickle digit (index finger) divided by the fourth digit (ring finger) tends to be lower in men than in women.This 2D:4D digit ratio is often used as a proxy for prenatal androgen exposure in studies of human health and behavior.For example, 2D:4D ratio is lower (i.e.more "masculinized") in both me