Across the animal kingdom, menopause is something of an evolutionary blip. We humans are one of the few animals to experience it. But Sam Ellis, a researcher in animal behavior, argues that this isn't so surprising. "The best way to propagate your genes is to get as many offspring as possible into the next generation," says Ellis. "The best way to do that is almost always to reproduce your whole life."

So how did menopause evolve? The answer may lie in whales. Ellis and his team at the University of Exeter recently published a study in the journal Nature that studies the evolution of menopause in the undersea animals most known for it. What they uncovered may even help explain menopause in humans.

Curious about other animal behavior mysteries? Email us at shortwave@npr.org.