Mean Genes

Big testicles for papa

Chimpanzees testicles are HUGE – they look like baseballs. Why? Chimps who produce the most sperm become fathers. Fertile chimpanzee females have sex dozens of times a day with as many males as possible.

Because chimp females are so sexual, sperm from many males fight for fatherhood inside female wombs. The chimps who want to win these sperm wars must bring a lot of troops to the battle, hence the baseballs between their legs.

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