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What Killer Whales Say About Menopause In Humans

Photo from Pixabay

Menopause is an eventuality for females, and is a fact of life. But until now, scientists have not managed to fully explain this biological event. Only three species on the planet experience it: humans, killer whales and short-finned pilot whales.

In hopes of further delving into this, a new study takes a look at killer whales and suggests that reproductive conflict between mothers and daughters may play a big part in how menopause has evolved, the New York Times reports.

Researchers analyzed four decades of data on killer whales in the Pacific Northwest, and discovered that when mothers and daughters reproduce at the same time, the calves of older female whiles were more likely to die than those of younger whales.

Killer whales generally start breeding at 15 years old, and stop in their 30s to 40s, but can live to be more than 90 years old. This means that they can spend up to two-thirds of their lives not producing offspring, which would seem biologically counter-productive.

Darren Croft, a professor of animal behavior at the University of Exeter in England and one of the study’s authors, says the unique relationships among killer whales may motivate the younger ones into being more competitive at reproduction. The whales are matriarchal, with offspring sticking by their mothers alone throughout their lives.

Croft says,

When females are born, they have a relatively low relatedness to the males in their group, because their father isn’t around. But as a female starts to reproduce, her relatedness to males increases, because her sons stay with her.

The researchers theorized that since young females are related to fewer males in their pods, they are more invested in competition, perhaps by hoarding resources or fighting with other members. Older females that have more offspring, and therefore are related to more members, are more cooperative.

The group took a look at 200 whales over 43 years, and found that their theory had evidence. This can then be translated to human menopause. However, other scientists argue that there are other reasons menopause might exist, such as the “grandmother hypothesis” that states menopause happens so that women can help improve their grandkids’ chances for survival.

The study was published in Current Biology.

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