Most animals die around the same time that they stop reproducing, but killer whales thrive and help their families find food after they hit menopause.
These findings could provide insight into the evolutionary reasons why human women often live long lives after they can no longer bear children, the University of Exeter reported. Two species of whale, and humans, are the only animals in nature observed to live for many years after menopause.
Female killer whales can generally only breed between the ages of 12 and 40, but they often live to be upwards of 90 years old. Past studies have suggested menopausal females increase their children's and grandchildren's chance of survival, but the reason behind this was unclear until now.
This new research suggests older female killer whales act as "repositories of ecological knowledge," and lead their families to the best salmon-foraging grounds. Since wisdom tends to accumulate with age, older whales hold information that could be useful to their families in times of hardship. Salmon shortages are a major contributor to mortality in whale populations across all age groups.
"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.
Humans did not develop the ability to record knowledge for the majority of our evolution, so a similar benefit to survival beyond menopause could have been seen in our early history.
"In humans, it has been suggested that menopause is simply an artefact of modern medicine and improved living conditions," said Professor Darren Croft of the University of Exeter. "However, mounting evidence suggests that menopause in humans is adaptive. In hunter-gatherers, one way that menopausal women help their relatives, and thus increase the transmission of their own genes, is by sharing food. Menopausal women may have also shared another key commodity - information."
The findings were published in a recent edition of the journal Current Biology.
