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Your fingers may hold a secret of human brain evolution
ScienceDaily • • science
Key Points:
- Professor John Manning and colleagues studied the 2D:4D digit ratio, an indicator of prenatal estrogen and testosterone exposure, by measuring the finger lengths of 225 newborns and comparing these with head circumference.
- They found that boys with higher 2D:4D ratios, suggesting higher prenatal estrogen, tended to have larger head circumferences, a pattern not observed in girls.
- This finding supports the estrogenized ape hypothesis, which links the evolution of larger human brains with feminization of the skeleton and changes in hormonal exposure during development.
- The study suggests evolutionary trade-offs where increased brain size may have provided advantages despite associated biological costs in males, such as higher risks of heart problems, infertility, and schizophrenia.
- Researchers emphasize that digit ratio is an indirect marker of prenatal hormone exposure and the study highlights associations that could shed light on the hormonal influences in human brain evolution.
