"Why Killer Whales Go Through Menopause But Elephants Don’t"

"Animals almost always continue to reproduce until they die. There are just three exceptions that we know of: humans, short-finned pilot whales, and killer whales. In all three species, females lose the ability to have children, but continue living for decades after. That’s menopause. Female killer whales go through in their 30s or 40s. Why? Why sacrifice so many future chances to pass on your genes to the next generation?

One of the most compelling explanations is called the grandmother hypothesis. Proposed in 1966, it suggests that older females forgo the option to bear more children so they can support their existing ones. By helping their children and grandchildren to survive and thrive, they still ensure that their genes cascade down the generations...
By ploughing through the data, student Emma Foster showed that if a male orca’s mother died before his thirtieth birthday, he was three times more likely to die the next year. If she passed away after he turned thirty, he was eight times more likely to subsequently snuff it. And if mum had gone through menopause, his odds of dying went up by fourteentimes. The data were clear: mothers help their sons well into adulthood, and older mums are especially helpful."
http://phenomena.nationalgeographic.com/2015/03/05/why-killer-whales-go-through-menopause-but-elephants-dont/

Interesting. Also, though, can we stop talking about non-Western humans like they are not humans? "Among many hunter-gatherers, like the Ache of Paraguay or the Hadza of Tanzania, around half of women survive to 45, and continue living into their late 60s. Like killer whales, they live long after the stop reproducing. And like killer whales, the longer they live, the more they know."