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Story summary
- Professor John Manning reports that in a study of 225 newborns, boys with higher 2D:4D digit ratios have larger head circumferences, implying greater brain size.
- The correlation was not observed among girls.
- These results support the estrogenized ape hypothesis, which posits increased brain size may carry health trade-offs like higher rates of heart issues and infertility.
- The study highlights prenatal hormones as a factor in shaping human development.
