Human evolution has long been tied to growing brain size, and new research suggests prenatal hormones may have played a surprising role. By studying the relative lengths of index and ring fingers — a ...

A study of 225 newborns suggests prenatal estrogen may have played a role in the evolution of larger human brains. Boys with finger-length patterns linked to higher estrogen exposure before birth ...

A new study, published July 6, 2026, in the journal Nature Communications, suggests that two of the best-known trends in human evolution—brain growth and the reduction in the size of the face and ...