Menopause is often seen as an unfair biological event, something that only those born with female reproductive systems must endure. It adds to the list of unique challenges—menstrual cycles, pregnancy, childbirth, and the career pauses while caring for infants—that are part of the female experience. And then, of course, menopause comes along, signaling a sharp drop in hormones that can feel disruptive and unnecessary.
But it turns out, there may be a reason for menopause after all. Scientists have studied the phenomenon across various species, and not every female animal undergoes a shutdown of reproductive organs as humans do. For most animals, reproduction continues until death unless medical issues arise or they are in captivity. However, there are three species of mammals that live for a significant time after their reproductive years: orcas, short-finned pilot whales, and humans.
This finding led to the development of the “grandmother hypothesis,” which suggests that these female mammals live longer to help ensure the survival of their species. Both whales and humans support their daughters in caring for their children, allowing the daughters to have more offspring. In the case of whales, grandmothers even assist in providing food for their grandchildren, freeing up their daughters to reproduce sooner.
A 2009 study, published in the National Library of Medicine, further explored this idea, noting that women who remain active beyond their fertile years may boost their daughters' reproductive success by helping care for their grandchildren. This, in turn, may enhance lifetime fertility. As a result, the genes of these older, more vigorous grandmothers would be more likely to persist in future generations.
Interestingly, chimps, our closest animal relatives, present a contrasting case. While most chimps reproduce until death, a specific group of chimps in Uganda’s Kibale National Park, known as the Ngogo chimps, experience menopause at around 50, similar to humans. However, unlike humans and whales, these chimps do not help care for their grandchildren, and once the daughters reach maturity, they leave their mothers. This behavior, along with their unusually long lifespans, is likely influenced by their access to an unnatural environment with abundant food, including more meat, which is not typical for chimps in the wild.
Research conducted over a 20-year period showed that the Ngogo chimps have extended lifespans within the park, living into their 60s compared to nearby wild chimps, who rarely live past 50. This deviation from typical chimpanzee behavior has led some scientists to question the general applicability of the grandmother hypothesis, especially in species living in captivity or protected environments.
Nevertheless, studies such as a 2018 paper in Ecology and Evolution reinforce the idea that only three species, including humans, live beyond menopause. Humans, in particular, spend a substantial portion of their lives—40-70%—post-menopause. While the grandmother hypothesis is still debated, it suggests that menopause may have evolved to help ensure the survival of our species, particularly since women tend to live longer than men.
So, grandmas, no pressure! You may just be playing a key role in ensuring the survival of the human race.