The relationship between digit ratio and sexual orientation in a Chinese Yunnan Han population

Abstract Digit ratio, particularly the second to fourth digit ratio (2D:4D), is fixed before birth and is related to male sexual orientation; moreover, ethnicity may affect the digit ratio. We take photocopies of both hands of 308 men of Han ethnicity, and we explored the relationship between the 2D:4D ratio and sexual orientation among the three groups (121 homosexual men, 50 bisexual men and 177 heterosexual men). The results showed: (a) the digit ratio of the men presented the trend as follows: 2D:3D