Defined broadly, menopause is the programmed end of fertility in a female animal. Human women, of course, are well aware that their fertility will decline with age and cease after a certain point, typically around age 50. In the animal kingdom at large, however, menopause is an oddity — and a long-standing evolutionary mystery. An organism’s ultimate goal is reproduction. Why sacrifice that consummate purpose? Even more puzzling, why would an animal naturally become infertile and then go on living for years? Throughout history, scientists have proffered numerous theories. But studying the biological phenomenon of menopause is difficult, in part because it seems to be so rare.

Lenny Letter, on the menopause for millennials beat.