This is from an answer in other question, about the age at which menopause occurs:
Aristotle's assessment was similar to those of Hippocrates and also Roman authors, so it seems that 2000 years ago most women entered the menopause in their early 40s. Mediaeval authors, however, gave the 50s as the age when menses ceased-much closer to the timing for twentieth century women.
Considering that, throughout history, menopause starts at about 40-50 years, shouldn't this point to a stable and long life expectancy? (Considering also that menopause is an adaptation.) When we read that humankind used to live much less than today, isn't it just the effect of newborn mortality, and thus adults lived just about as long as we do today?