Unlike the perennial question posed by your grandkid – “Why is the sky blue?” (which you know has some answer principled in physics and light theory that you simply just can’t regurgitate) – the answer to “Why do we go through menopause?” is very simple. You can honestly reply, “We don’t know.” We do know that even in ancient times, it appeared that women would go through menopause roughly at the same age as we do today – that is if they survived that long. (Women living in Roman times would be lucky to reach 30 years old!). So some would say that menopause simply occurs because we have pushed our life expectancies way beyond historical norms. However, other species known to live many decades, such as elephants, don’t go through a menopause and like almost all other species continue to reproduce practically right up to the end of their life expectancies. Why women now spend much of their lives unable to bear offspring is somewhat of a quirk of nature.
The reason menopause is puzzling is because of the evolutionary view that the species that survive are those that can best continue to bear offspring. And the corollary to this is that those best able to compete for resources are the ones that are the most successful. So what is it about menopause that may have helped us survive? A starting point for research is to look for other species that go through menopause. The list is short – basically only orca whales and pilot whales. Orca whales can live to about age 90 and quit reproducing around age 50; pilot whales have a slighter shorter life span, but also quit bearing offspring years before they die. Orca whales are quite special to those of us living in the Pacific Northwest. They travel up and down our coastline, and their activities and whereabouts are frequently featured on local news stories. Scientists studying them have learned much of their behaviors and have come up with a theory that may explain why they go through menopause – dubbed the “Grandmother Hypothesis.” This basically states that there is an evolutionary advantage for the grandmother of a species to lose reproductive ability when her children start bearing offspring. In the case of the orcas, it has been observed that the older females are the ones that lead their families known as pods, to the best fishing areas. She is able to do this best without being encumbered by having to nurse and care for a young calf. In this way she not only is able to preserve her own strength to continue this role, but assist in catching and sharing salmon with the pod – which better secures the survival of her own daughters and their offspring – who remain in the pod for life.
This grandmother hypothesis may explain why humans have followed a similar path, although one would need to assume that historically women survived longer than we typically believe – which seems unlikely. However there is some research that supports this theory. Remnants from a few ancient “hunter-gatherer” cultures have been discovered where archeological clues suggest that their life spans went beyond expected and evidence suggests that the oldest women played a major role in providing food and caring for their grand-children. There are also some tribes in remote Africa that typify this model where the matriarch plays a major role providing leadership and survival skills for extended family units.
We may never know for sure why we humans have this relatively unique tendency to live so many years beyond the time we can bear offspring. From my perspective, it probably is in many ways desirable not to have to think about having children when we are in our 60’s and 70’s. However, I wish that we didn’t lose our hormones at the same time we lose our eggs. Living years without estrogen has its consequences
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