Can anyone guess what we have in common with female orcas (killer whales}?
That’s it. We share menopause with only two species on the planet, and both are whales: the orca (killer whale) and the pilot whale (which is technically a dolphin). All other mammals, including gorillas, chimpanzee, elephants, dogs, cats, and camels continue to bear young, albeit with decreasing frequency, until they die. No other mammal experiences literally decades of post-reproductive life.
Except us and the whales.
Of course, the big question biologists ask is, Why? From a Darwinian perspective, bearing young assures the continuation of the species. Decades of life without fertility makes no evolutionary sense. (According to biologists; we, on the other hand, might feel otherwise.)
Now, after decades of closely observing a specific pod of killer whales in the Pacific Northwest, biologists have greater understanding of the role female elders play in the whale community. The almost eerie parallels to our human experience have piqued the interest of scientists and writers, who think perhaps the way of the orca may shed light on human menopause.
For years, scientists thought human menopause was simply due to medical advances that enabled women to outlive their normal genetic lifespan. Without the intervention of modern medical technology, so the thinking goes, we too would bear children until we died, like our close mammalian cousins. Evolution, remember, favors traits that support the passing on of a species’ genes.
Enter the orca.
Female orcas stop calving in their 30s and 40s, but they continue to live for many decades beyond that—well into their 80s. “Granny,” the oldest of the Northwest orcas, is thought to be over 100 years old. After decades of observation, including hundreds of hours of underwater video, scientists began to understand that these old gals weren’t just freeloading on their sons and daughters. They were critical to their survival.
Orcas mostly hunt salmon, stocks of which vary, sometimes greatly, from year to year. It is the older female orcas that tend to lead the pods, and this is especially noticeable when the salmon stock is low. During lean years, the older females more frequently lead the clan. At those times, the accumulation of knowledge and experience by the older females give the orca a critical edge.
“That kind of knowledge is accumulated over time—accumulated in individuals,” said Darren Croft, professor of animal behavior at the University of Exeter in this article.
Studies of death rates were also revealing. The whale clans are matrilineal, with sons and daughters staying with the mother for life. Mature sons are so dependent, in fact, they are called “mummy’s boys.” They leave the clan periodically to mate, but they return to follow their mothers. When an older female dies, her sons and daughters are more likely to die as well. In fact, a son is eight times more likely to die within the year after losing his mother.
While these characteristics don’t exactly parallel human experience (we don’t tend to enjoy having our aging sons follow us around), they do point to the critical role of older females to the survival of the clan, whether whale or human.
Recent studies of hunter-gatherer societies reinforce this hypothesis. Given the long and costly job of raising human children to adulthood, grandmothers play a critical role in the well-being of the family, often taking on the role of forager-in-chief and caregiver for a daughter’s children.
It’s called the “grandmother effect.” Evolutionary biologists hypothesize that these contributions of an older woman offsets the decades of infertility. The grandmother assures that her genes are passed along by making sure that her grandchildren survive.
By no means do the grandma orcas take a back seat to the kids. They remain spry, vital, and active into their advanced years, maintaining their role as guide and coach. But the old gals have also been seen cavorting sexually with young males, presumably to teach them a thing or two about the birds and bees—and the cetaceans.
“Besides being the repository of knowledge about where to go in case of lack of food, they also lead very rich lives,” says Deborah Giles, director of the Center for Whale Research.
And so do we. This evolutionary state of affairs wherein we enjoy decades of vigorous, post-reproductive life while contributing to the well-being of our kin and the world in general is a pretty happy state of affairs, I’d say.
If the whales are any indication, far from being redundant, useless, or invisible, we continue to fill important and meaningful roles after menopause, which we have garnered through years of experience.
“We complain, women of my age, of becoming invisible, and it's true—you realize how very much you're defined by sexuality. But I have a sense—galvanized by stories about the killer whales—that now is the time when you become the person you really want to be," writes journalist Christa D’Souza, author of The Hot Topic, a book about menopause.
“The idea of women passing on information; the idea of wisdom with age—there's a beauty in that that is about something other than being able to reproduce.”