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

vervet monkey

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

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