Ask any woman who’s experienced it, and she’ll tell you menopause is no picnic. But, human women have it easy compared to the rest of the animal kingdom: Save for orcas and one other whale, female mammals tend to die shortly after birthing their last child. Now, researchers from the University of Exeter have found the reason for these exceptions: Post-menopausal killer whales are able to share invaluable information with the rest of their pod.
“Our results show for the first time that one way post reproductive females may boost the survival of their kin is through the transfer of ecological knowledge. The value gained from the wisdom of elders can help explain why female killer whales and humans continue to live long after they have stopped reproducing,” said Lauren Brent of the University of Exeter’s Centre for Research in Animal Behaviour.
The team studied 35 years of data covering 102 killer whales, including birth and death dates, as well as more nuanced data like genetic and social relationships. They found that when foraging for salmon, older females tended to take on leadership roles. This was especially prominent during lean times, when salmon were hard to find. The researchers believe the matriarchs’ stored experience helps their pod survive when they otherwise wouldn’t.
They also found that menopausal females tend to lead their sons more than their daughters. From a reproductive perspective, this makes sense: Males offer a greater payoff in their ability to carry on the mother’s genes, especially when mating outside the group.
This behavior puts killer whales into an elite group of mammals, as only human women and one other species of whale tend to live beyond menopause. For other species, surviving past their reproductive prime doesn’t make much sense – a female incapable of passing on genes only serves to consume resources. But in intelligent, pro-social species like whales, the knowledge acquired by older members can have a demonstrable net benefit on the group.
The findings shed some light on human evolution, as well. Menopausal survival in humans is often attributed to things like improved medical care, societal norms, etc. But, this sort of research suggests that menopause is adaptive for us, as well. Given that the ability to read and write is an exceptionally new phenomenon, all knowledge would have to be retained mentally. Knowledge of what’s safe to eat, or where to find food, would have been invaluable to our ancestors.
