2012 SCIENCE NEWS TOP 25: 8
For more than 50 years the matter had been considered settled: A woman grows all the eggs she will ever have before she is even born. But a study published this year, and then contested, suggests that this long-accepted fact may not be true.
Stem cells in the ovaries of both women and mice replenish egg supplies throughout adulthood (SN: 4/7/12, p. 8), reported a team led by Jonathan Tilly, a reproductive and developmental biologist at Massachusetts General Hospital. With aging, the stem cells’ capacity to make eggs diminishes, eventually petering out at menopause, Tilly says.