Eve: How the Female Body Drove 200 Million Years of Human Evolution

by Cat Bohannon

This is presumably what happened to my friend’s wife. Like nearly every woman on the planet, she was born with roughly a million immature egg follicles. But every year since, thousands of her follicles died off and were reabsorbed by her body. By the time she became a teenager, she had only about 300,000 to 400,000 follicles left. From then on, she lost about a thousand of them every month. If she started ovulating at age thirteen, she was destined to run out of eggs somewhere in her early forties. Which is precisely when most women stop being able to get pregnant without medical assistance. My friend had been on the Pill for many years, which you might assume would have saved some of her eggs. But no—delaying the ovulation process by going on the Pill doesn’t save your eggs. In fact, every year of being on high-dose hormonal birth control seems to move the start of menopause up by about a month.[*5] That’s because the loss of egg follicles isn’t triggered by ovulation. Instead, ovulation saves about 20 follicles a month from early death, of which usually only 1 will go on to become a mature egg and find its way down the fallopian tube. But for those 20 that are saved, 980 die off.