By Mark Green and Andrew Pask
In prenatal ultrasounds or at delivery, many new parents look between their baby’s legs: the presence of a penis is taken as a strong sign that it’s a boy.
For humans and other animals, development of a penis was thought to be driven by “male hormones” (androgens) produced entirely by the testes of the male fetus as it grows in the uterus.
However, a new paper released today indicates this might not be the case.