2nd to 4th digit ratio and offspring sex ratio.
There is evidence that the ratio of the length of the 2nd and 4th digit (2D:4D) is negatively related to prenatal and adult concentrations of testosterone. It has also been reported that high levels of testosterone at conception in both fathers and mothers are associated with an increased sex ratio (proportion of males at birth). It follows from these observations that low values of 2D:4D may be related to high sex ratio. We present evidence from three populations (English, Spanish and Jamaican) that 2D:4D is negatively related to sex ratio, independent of the sex and ethnicity of the parents.
Population Biology Research Group, School of Biological Sciences, University of Liverpool, Liverpool, UK. jtmann@liverpool.ac.uk
J T
JT
Manning
S
S
Martin
R L
RL
Trivers
M
M
Soler
D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D004739:England; D005260:Female; D005385:Fingers / Q000033:anatomy & histology*; D006801:Humans; D007563:Jamaica; D008297:Male; D008875:Middle Aged; D012044:Regression Analysis; D012727:Sex Characteristics; D012744:Sex Ratio; D013030:Spain