eli5: Why do women only have their period/ are fertile for approximately 50 years if they’re born with millions of eggs?


I’m an uneducated man on this subject. Please don’t judge. I thought women release a single egg every cycle normally and that would add up to about 600 eggs in a lifetime, if that were the case. Thanks for the knowledge!

In: 1

When the ovaries develop in utero, there are about 6 million eggs in them. By the time the baby is born, there are 1-2 million. Before puberty, a girl loses about 10,000 eggs per month. After puberty, her hormones have a protective effect and she only loses about 1,000 a month.

After puberty, only one egg matures and drops per month; the rest just resorb.

This explains it in more detail: https://www.healthline.com/health/womens-health/how-many-eggs-does-a-woman-have#eggs-lost-each-month

During every cycle, the best egg at the time is released that has the highest chance of fertilization. This means there’s competition every month which increases reproductive chances. If there were only 600 eggs then there wouldn’t be competition and if a bunch of eggs were damaged for any reason then this would decrease reproductive chances and introduce unintended mutations.

Because we evolved from animals that released millions of eggs in their lifetime and thousands at once. There is no evolutionary pressure for you to produce fewer eggs even though we evolved to produce very few offspring.