The Enigmatic Evolution of Menopause

By: Red Hot Mamas

Published: May 26, 2010

“Along with big brains and upright posture that every text of human evolution emphasizes, I consider menopause to be among the biological traits essential for making us distinctively human—something qualitatively different from, and more than, an ape.” -Jared Diamond, 1996

The evolution of menopause is a mystery that researchers have yet to unfold. We are an extraordinary species of the animal kingdom. Homo sapiens have tremendous psychological capacities. The nature of our behavior is complex as is our ability to rationalize it. We are the most intelligent of all living beings on Earth although we share many similar biological characteristics to our evolutionary primate cousins, the gorilla.

Gorillas are the second closest living relative to humans (after the chimpanzee).1 In fact, human DNA is 98% identical to a gorilla’s.2 Our blood proteins, immune responses and biochemical makeup are very similar.3 The genetic similarities have recently lead scientists to apply human health questions to gorillas. As a result, new discoveries about human health have come to light by studying the gorilla.

Menopause was once thought to be unique to our species. Evolutionary biologists are rethinking this claim due to recent findings from a study of gorillas at the Brookfield Zoo in Brookfield, Illinois. Research scientists and primate specialists Dr. Sylvia Atsalis and Dr. Sue Margulis in collaboration with the National Institutes of Health (NIH) designed a study to examine gorilla menopause. “As primates, humans and gorillas share many important physical traits. Our findings underscore those similarities and the parallel between humans and gorillas, our evolutionary cousins, who may be good models for an improved understanding of menopause,” says Dr. Atsalis describing the gorilla menopause study.

The gorilla lifespan is significantly less than a human’s.3 Nevertheless, gorillas (and a handful of other primates) continue to live well past their reproductive years. Among the only other species on Earth that is known to live past this stage are pilot whales, elephants and the human being. Most other species continue reproduction until death, maximizing their number of offspring. While you are fanning your hot flashes away, keep in mind menopause somehow has a positive effect on our species. How is menopause an evolutionary advantage for humans, gorillas, elephants and whales?

Grandmother Hypothesis

Dr. Jared Diamond, a physiologist from the University of California Los Angeles states, “Any theory of menopause evolution must explain how a woman’s apparently counterproductive evolutionary strategy of making fewer babies could actually result in her making more. Evidently, as a woman ages, she can do more to increase the number of people bearing her genes by devoting herself to her existing children, her potential grandchildren, and her other relatives than by producing yet another child.”4

What Dr. Diamond is referring to is the grandmother hypothesis. The hypothesis is often used to explain the evolutionary mystery of our reproductive physiology including menopause. The hypothesis is based on the concept that menopause is an adaptation that makes grandmothering possible5. The grandmother nurtures her offspring by fostering both physical and social support. In a very simplified explanation, grandmothers provide wisdom for their progeny to survive longer. Further, the risk of death from child delivery increases with age. According to this hypothesis, an older woman can contribute more to her species by helping her relatives grow and develop during their reproductive prime, rather than by taking the risk of producing more children.

An anthropological view offered by Dr. Kristen Hawkes of the University of Utah states, older women may have been essential to the survival of our species in prehistoric times6. Prehistoric “grandmothers” could have created the spare time our ancestors needed by “babysitting” allowing them to explore and migrate our species across the globe. On the contrary, some scientists believe menopause may not have existed in ancient societies.

Other Evolutionary Theories of Menopause

Menopause may be a recent adaptation to our species as a byproduct of an increased lifespan. Dr. Diamond finds that the rise of agriculture and increase in human survival skills in the last 40,000 years has allowed our species to live longer, healthier lives.4 To this end, it is only in the relatively recent past that our species has lived beyond 45 or 50 years old. Therefore, women could not have lived past their reproductive years eliminating the possibility for a menopause.

Conclusions

While you are pondering your aging skin, and hot flashes wondering “why me?!” it should be a relief to know that we are not the only species on this planet going through menopause. While gorillas may not have hot flashes, mood swings or moodiness, it is still good to know we are not the only ones. The gorillas are on our side! By studying these mighty primates, we can better understand the physiological changes associated with menopause. We may finally have some help resolving issues associated with the onset of menopause including osteoporosis, heart disease, diabetes and other concerns. Researchers will also benefit by finding a resolution to the evolutionary mysteries of menopause.

Questions still abound, of course. The why of the menopause we may never know; the how we are beginning to understand; the variation in the when of this human universal remains as a fascinating issue for further exploration.” –Andrew J. Petto

1 Chimps Belong on Human Branch of Family Tree, Study Says, James Pickrell, National Geographic News: May 20, 2003

2 Wikipedia Encyclopedia definition of “human”

3 Wikipedia Encyclopedia definition of “gorilla”

4 Dr. Jared Diamond’s July, 1996 article in Discover Magazine

5In 1996, Dr. Peccei of the University of California Los Angeles Department of Anthropology introduced the “new” grandmother hypothesis. In this hypothesis, the “grandmothering is an adaptation facilitating increased longevity, and menopause is the byproduct”.

6 Dr. Hawkes’ beliefs are supported by her studies of the Hadza tribe in Tanzania.

7The Evolution and Ecology of the Menopause-Science Tribune, March 1998.

Other sources of information:

Brookfield Zoo Research

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