Why do most women get their first period around age 12 when their bodies are usually not well developed enough to safely carry a baby to term?

Question

Why do most women get their first period around age 12 when their bodies are usually not well developed enough to safely carry a baby to term?

In: 12558

Answer 1

I don’t know if this is really the answer but I would like to add this:

My gyno once explained to me that during their periods, the girls’ bodies make some certain hormones that help develop their bones structure and shape. So I guess that part of why we get it so much earlier than we actually are able to birth is because it helps us get ready for birth.

Why humans are the only primates that get periods like this, I don’t know, however. Neither when along the evolutionary line we started, although I’d be very interested if someone knows.

EDIT: I stand myself corrected, we are not the only primates who menstruate, apparently some others do, too. Please read the comments below for more clarification on these questions (: