Of Mice and Menopause

The startling discovery that mammals may constantly make new eggs could trigger a biological revolution

The conventional story of female fertility has never made a whole lot of sense. A few months before the birth of a little girl, textbooks have said for 50 years, her ovaries contain about 1 million egg cells each--all that she will ever have. Those numbers only go down as eggs deteriorate or get washed out of the body during menstruation. Finally, when a woman is about 50, they're essentially gone, signaling the hormonal changes known as menopause. The story fits the evidence. Autopsies prove that women have lots of eggs to start with and that the number steadily declines. But...

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