Victoria Gill in BBC:
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. But female orcas and women evolved to live long, active, post-reproductive lives. “From an evolutionary perspective, it's very difficult to explain,” says Prof Darren Croft, who travels here from the UK's University of Exeter to study the whales. “Why would an individual stop having their own offspring so early in life?” Darwinian evolutionary theory says that any characteristic reducing an animal's chance of passing on its genes to the next generation will be edged out – the process of natural selection. That has led some to argue that menopause in humans is a result of longer life, better health and better medical care. But, as well as painting a rather depressing image that post-menopausal women are simply alive beyond their evolutionarily prescribed time, that theory has been largely debunked – thanks, in part, to these orcas. Obviously, medical care is not increasing their lifespan. “So studying them in the wild could help us reveal some of the mystery of why menopause evolved,” Croft says
…Some of their latest insights came from analysing hundreds of hours of video footage of the whales going about their lives – chasing the salmon on which they depend for sustenance. “We noticed that the old females would lead from the front – they're guiding their groups, their families, around to find food,” says Croft. Crucially, he and Franks also noticed that the older females took the lead more often during years when salmon supplies were low – suggesting that the pod might be reliant on their experience, their ecological knowledge. “It's just like us,” says Croft. “Before we had Google to ask where the shop was, if there was a drought or a famine, we would go to the elders in the community to find out where to find food and water. “That kind of knowledge is accumulated over time – accumulated in individuals.”
More here.
