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Researchers look to whales to try to understand how and why menopause evolves

A MARTÍNEZ, HOST:

All right. Now for a deep dive into whales - and menopause?

LEILA FADEL, HOST:

Yes, menopause - when a female's menstrual cycles ends, and so does the ability to give birth. Now, very few animals are known to experience menopause, but some whales do. Sam Ellis teaches animal behavior at the University of Exeter, and he was the lead on some new research recently published in the journal Nature.

SAM ELLIS: What we were interested in doing with this study was to try and use whales as a model to understand how and why menopause evolves.

MARTÍNEZ: The team looked at toothed whales, such as orcas, belugas, narwhals, short-finned pilot whales and a species known as false killer whales.

ELLIS: If you think the aim of evolution is to get as many offspring as you can into the next generation, almost always the correct way to do that - the easiest way to do that - is going to be to reproduce for your whole life.

MARTÍNEZ: But he says menopause may give these whale species an evolutionary advantage.

ELLIS: If mothers and daughters are reproducing at the same time, living in close association, and there are limited resources, there's competition for those resources.

FADEL: Which supports the so-called grandmother hypothesis that when older females in some species stop reproducing, they can help the whole family group succeed.

ELLIS: Toothed whales with menopause live much longer than you'd expect given their size. So all the species without menopause were on a really straight line, and the species with menopause are way above it. They are living much, much longer than expected.

MARTÍNEZ: That extended lifespan creates greater opportunity for overlap between generations and creates intergenerational families in the oceans, just like some humans do on land.

(SOUNDBITE OF IHF AND IAN URBINA'S "BRIDGE") Transcript provided by NPR, Copyright NPR.

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