The 2nd:4th digit ratio, sexual dimorphism, population differences, and reproductive success:: evidence for sexually antagonistic genes?

The ratio between the length of the 2nd and 4th digit (2D: 4D) is sexually dimorphic, with mean male 2D:4D lower than mean female 2D:4D. It recently was suggested that 2D:4D is negatively correlated with prenatal testostcrone and positively correlated with prenatal estrogen. It is argued that high prenatal testosterone and low estrogen (indicated by low 2D:4D) favors the male fetus and low prenatal testosterone and high estrogen (indicated by high 2D:4D) favors the female fetus, The patterns of expression of 2D:4D are interpreted in terms of sexually antagonistic genes. We report data on the following, (a) reproductive success and 2D:4D from England, Germany, Spain, Hungary (ethnic Hungarians and Gypsy subjects), Poland, and Jamaica (women only). Significant negative associations were found between 2D:4D in men and reproductive success in the English and Spanish samples and significant positive relationships between 2D:4D in women and reproductive success in the English, German, and Hungarian samples, The English sample also showed that married women had higher 2D:4D ratios than unmarried women, suggesting male choice for a correlate of high ratio in women, and that a female 2D:4D ratio greater than male 2D:4D predicted high reproductive success within couples. Comparison of 3D:3D ratios of 62 father:child pairs gave a significant positive relationship. This suggested that genes inherited fi om the father had some influence on the formation of the 2D:4D ratio. Waist:hip ratio in a sample of English and Jamaican women was negatively related to 2D:3D. (b) Sex and population differences in mean 3D:3D in samples from England, Germany, Spain, Hungary (including ethnic Hungarians and Gypsy subjects), Poland, Jamaica, Finland, and South Africa (a Zulu sample). Significant sex and population differences in mean 2D:4D were apparent. (C) 2000 Elsevier Science Inc. All rights reserved.