Your fingers may hold a secret of human brain evolution
Researchers are investigating the 'estrogenized ape hypothesis,' which suggests that prenatal estrogen exposure influenced human brain evolution. By measuring the ratio of index to ring finger lengths in newborns, scientists found a correlation between higher estrogen exposure and larger head circumference in boys.
Why it matters
Understanding the biological drivers of human brain evolution provides deeper insight into our species' development and cognitive origins.
Human evolution is closely associated with the development of a much larger brain. New research suggests that greater exposure to estrogen before birth may have contributed to that expansion, and that a possible trace of this hormonal influence can be seen in the relative lengths of a person's fingers.
Professor John Manning, a member of Swansea University's Applied Sports, Technology, Exercise and Medicine (A-STEM) research team, specializes in the study of digit ratio.
Digit ratio compares the length of the index finger, known as 2D, with the length of the ring finger, known as 4D. This measurement is called the 2D:4D ratio. Researchers use it as an indirect indicator of the balance of estrogen and testosterone a fetus may have been exposed to during the first trimester of pregnancy.
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