Menopause Messages from the Orcas

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One day while driving to Trader Joe’s to shop for groceries, I was listening to NPR and a story came on about menopause. Being of a “certain age” I was eager to hear what the report was about. I sat there listening in fascination as the scientist divulged that “only three known mammals experience the menopause - orcas, short-finned pilot whales and we humans. Even our closest ape cousins, chimpanzees, do not go through it. Their fertility peters out with age and, in the wild, they seldom live beyond childbearing years.” Whoa! Only 3 species of mammals experience menopause. It had never occurred to me that menopause in the animal kingdom was so rare. And why is that so? Why do 3 of the animals with the highest brain functions go through this phase of life? When I returned home, excited to learn more, I found an article by Victoria Gill with BBC News* (I think she was the person I heard being interviewed), which chronicles her experience with pods of orcas in the coastal area of the North Pacific, close to Vancouver and Seattle, known as the Salish Sea. She writes about Granny who is quite the celebrity in whale circles. You see Granny is the oldest know living killer whale, estimated to be between 80 and 105 years old.

Granny lives in a clan of 83 killer whales in three distinct pods all of which return to this area every summer. The study of this clan has been going on for 40+ years. Biologist have a particular interest in her and other females of the pod population because even though they stop reproducing in their 30s -40s, they have a “post-reproductive lifespan” or menopause, which is very unusual in the animal kingdom.

Researchers are fascinated by this cessation of reproduction because from the long-held Darwinian evolutionary perspective, this early cessation of reproduction doesn’t fit with the process of natural selection. Nor do they have access to better health care, a perspective that has been long suggested about menopausal women. So why are these orcas, and women, healthily living well beyond their gene-passing years? Is there a higher purpose to why menopause has evolved?

One compelling explanation has been the “grandmother hypothesis”, according to which a grandmother has a decidedly beneficial effect on the reproductive success of her children and the survival of her grandchildren. In the orca pods, the grandmothers are the leaders, aiding in the search for food and caring for the less able members of the pod. They are revered and respected for their experience and knowledge. However researchers have not found this to outweigh the genetic costs of being non-reproductive.

So what other factors could be driving the menopause evolution? One proposition researchers are now examining is “whether menopause helps the orcas survive by reducing the chance of mothers and daughters having babies at the same time” which would impact the pod’s female’s ability to provide food and parental care. Another factor they are examining is “whether calves have a better chance of survival when they have a post-menopausal grandmother.”

In our youth and sex centric society, my hope is that through this research we can turn the invisibility and irreverence of menopause into a phase of life that has purpose and is revered and respected. These orca grandmother’s certainly are modeling the importance and value of leadership and experience that only menopause can provide.

-Mary Seney Bucci - Director of Possibilities

*View the full article at http://www.bbc.com/news/magazine-37025092