Killer whales and the menopause
I have just been reading a fascinating article on the menopause in terms of human evolution. Why do we have the menopause when practically no other female mammals have anything remotely similar? Most animals reproduce throughout their lives (although fertility may decrease the older they get), even our nearest cousins in the ape family.
There are a number of reasons scientists give for this, mainly that human babies need their parents’ support for survival for at least 10 years and if you had babies in your 70s or 80s you wouldn’t be around to help them survive. Also, imagine the physical toll of having a baby at 70 and trying to raise it!
Interestingly, scientists had thought that the menopause is a modern change in that women are living longer and just run out of eggs. But they now think that the menopause goes all the way back to the stone-age. Studies of modern day hunter/gatherers whose lifestyles resemble those of stone-age cultures still have a menopause.
Among the Kung and Hadza of sub-Saharan Africa, women enjoy long lives after fertility ends and actually spend nearly half their adult life as post menopausal. A lovely explanation for this involves grandchildren. Evolutionary selection may have favoured those women who lived longest after childbearing years as they could contribute to bringing up their grandchildren – ensuring the survival of their own DNA! (Rock on Grannies!)
And where do Killer Whales come in? Out of all the mammalian species the Killer Whale is the only other animal that has a menopause. Like people, Killer Whales are very sociable, and family orientated, children live with their mothers and other female members for life. They often live right up to their 90s and like women they stop reproducing in their 30s and 40s long before they die!
I hope you’ve enjoyed reading this blog post.
