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](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2018/06/062818_AC_testicles_feat_option-b.jpg?fit=860%2C460&ssl=1)
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.
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