In most species, the females die once they hit menopause and can no longer reproduce. So why do human females live so long after they're no longer able to have children?
Well, one possible answer is known as the "grandmother hypothesis."
The idea is that a long time ago, somewhere along the human evolutionary line, something happened that made babies and children more dependent on their mothers and grandmothers in order to survive.
It could be that the changes in climate or geography forced early humans to migrate from a place where food was abundant, to a new area where food was scarce. In such an instant, for infants to live, all the women had to pitch in to find food for the babies, older women included.
If that's true, it makes evolutionary sense that women live well past menopause. The same logic holds up today. In modern hunter-gatherer tribes, grandmothers are usually the best foragers, freeing up younger women to spend less time looking for food, and more time reproducing.