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

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 < 2D:4D < 3D:4D < 2D:5D < 4D:5D < 3D:5D; (b) homosexual and bisexual men had higher mean 2D:4D ratios on their right hands than heterosexual men; (c) there was no difference between homosexual men and bisexual men in the 2D:4D ratio; (d)there was no difference between right and left hands in the same group in the 2D:4D ratio. These results indicate that prenatal sex hormones may influence sexual orientation in the Han ethnicity in Kunming, Yunnan, China. (C) 2016 The Authors. Published by Elsevier Ltd.