Why some mammal species don’t have descended testicles, but most do
Several mammal species have lost the genes needed for a ligament that controls testes location
AIRING OUT A vervet monkey displays descended blue balls in a thin, unprotected scrotum. The male ancestor of placental mammals also sported descended testicles, rather than undescended ones like a few mammal species, a new study suggests.
Jez Bennett/Shutterstock