Genetic and Environmental Influences on 2D:4D Finger Length Ratios: A Study of Monozygotic and Dizygotic Male and Female Twins
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Recent studies have shown significant sex differences in the pattern of 2D:4D finger length ratios in humans and several other mammalian species. In humans, these ratios are suggested to be negatively correlated with prenatal exposure to testosterone, positively correlated with prenatal estrogen, and exhibit sex specific patterns of association with sexually dimorphic clinical phenotypes. However, the relative contributions of genetic and environmental influences on digit ratios in men and women are currently unknown. Therefore, the purpose of the current study was to examine genetic and environmental influences on 2D:4D ratios in twins. Participants included 146 monozygotic (MZ) and 154 dizygotic (DZ) adult male and female twins participating in the Michigan State University Twin Study of Behavioral Adjustment and Development. Overall, biometric model-fitting analyses indicated significant additive genetic and nonshared environmental influences on digit ratios. Findings suggest greater similarity between 2D:4D ratios in MZ relative to DZ twins that can be accounted for by genetic and nonshared environmental factors.
KeywordsSteroid hormones 2D:4D Finger length ratios Sry Sex differences Twins
This research was supported by an individual undergraduate research grant “Dean’s Assistantship” and “Dean Gwen Andrew Undergraduate Research Award” from the College of Social Science at Michigan State University as well as an NIH joint Neuroscience Program Training Grant (NS07437) from Florida State University awarded to KLG.
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