Selective Breeding for a Behavioral Trait Changes Digit Ratio

@article{Yan2008SelectiveBF,
  title={Selective Breeding for a Behavioral Trait Changes Digit Ratio},
  author={Reginia H. Y. Yan and Jessica L. Malisch and Robert M. Hannon and Peter L. Hurd and Theodore Garland},
  journal={PLoS ONE},
  year={2008},
  volume={3}
}
The ratio of the length of the second digit (index finger) divided by the fourth digit (ring finger) tends to be lower in men than in women. This 2D∶4D digit ratio is often used as a proxy for prenatal androgen exposure in studies of human health and behavior. For example, 2D∶4D ratio is lower (i.e. more “masculinized”) in both men and women of greater physical fitness and/or sporting ability. Lab mice have also shown variation in 2D∶4D as a function of uterine environment, and mouse digit… 

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