Clues for the evolution of menopause in whales — and humans? : Short Wave Across the animal kingdom, menopause is something of an evolutionary blip. We humans are one of the few animals to experience it. But Sam Ellis, a researcher in animal behavior, argues that this isn't so surprising. "The best way to propagate your genes is to get as many offspring as possible into the next generation," says Ellis. "The best way to do that is almost always to reproduce your whole life."

So how did menopause evolve? The answer may lie in whales. Ellis and his team at the University of Exeter recently published a study in the journal Nature that studies the evolution of menopause in the undersea animals most known for it. What they uncovered may even help explain menopause in humans.

Curious about other animal behavior mysteries? Email us at shortwave@npr.org.

Most animals don't go through menopause. So why do these whales?

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EMILY KWONG, HOST:

You're listening to SHORT WAVE...

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KWONG: ...From NPR.

Hey, SHORT WAVErs. Emily Kwong here. And this time, I've got two of our favorites for our regular roundup of science news. Ari Shapiro is in the house. Hi, Ari.

ARI SHAPIRO, BYLINE: Hi. Thanks for letting me dish up some science knowledge with you.

KWONG: Yeah. And I also have Margaret Cirino. Hey, Marge.

MARGARET CIRINO, BYLINE: Hi, Emily.

KWONG: As you both know, we're going to share three science stories in the news that have caught our attention recently.

SHAPIRO: I hear one of them is about menopause in whales.

CIRINO: Yes.

SHAPIRO: The animal, not the country.

CIRINO: Yeah. And another is about an innovative patch that helps people with vocal disorders speak.

KWONG: And finally, we have a story about songbird migration and the birds' secret rest stops. All that on this episode of SHORT WAVE, the science podcast from NPR.

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KWONG: All right. Ari Shapiro, as our guest, which topic do you want to start with? What calls to you the most?

SHAPIRO: Such a difficult choice. They all three sound marvelous. But because I am partial to the human voice, can we start with this patch that helps people who have vocal impairments speak?

KWONG: Yeah. So a little backstory. The person who actually inspired me to become a journalist was this fantastic newspaper reporter up in Maine. His name was Doug Harlow, and he used a special device to speak. I interviewed him about it 10 years ago.

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DOUG HARLOW: (Through electrolarynx) Good afternoon. Doug Harlow calling.

KWONG: And the reason is because when Doug was in his mid-50s, doctors found throat cancer, so he had his vocal cords removed to save his life and in their place, he was given a hand-held, battery-powered device called an electrolarynx.

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HARLOW: (Through electrolarynx) I remember it being like a foreign appendage.

SHAPIRO: Wow.

KWONG: The device basically vibrates and Doug would hold it up against his throat, and with time, he learned how to turn those vibrations into the sound of words like you just heard. But now, a team at UCLA has figured out a new way to help people with voice disorders speak, no hands required.

CIRINO: Yeah. This is a type of patch that sticks directly to the skin on the throat. They published their research in the journal Nature Communications last week.

SHAPIRO: So this patch sticks onto the throat. And how does it work?

CIRINO: So the patch is about one square inch. It's made of this soft, stretchy material. Ari, I'm going to ask you to put your hand to your throat as you speak and just say a few words for me.

SHAPIRO: OK. My hand is on my throat like a hand scarf.

KWONG: (Vocalizing).

SHAPIRO: Yeah. Feeling vibrations here.

KWONG: Yeah. So that muscle movement that you feel, the patch can turn it into an electrical signal, which is then converted into audible speech that anyone can hear. Sounds a little like this.

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UNIDENTIFIED PERSON: (Through voice-changer patch) Merry Christmas.

SHAPIRO: Wow. The difference between the earlier version of the voice device and that is night and day.

CIRINO: Yeah.

SHAPIRO: Well, everybody has a different voice. Is this patch able to kind of decode all the different range of voices that there are in an accurate way?

CIRINO: Yeah. So the researchers developed a machine learning algorithm to correlate the electrical signal to certain words and the machine learns over time, since everyone's voice is different.

KWONG: Yeah. The device's inventor, Jun Chen, said his team has measured an accuracy rate of about 95%.

SHAPIRO: Is this device going to be commercially available any time soon?

KWONG: So Jun's team has to do a lot more tests to increase the vocabulary and translation accuracy of the patch, but if that pans out, he hopes something like this can be commercially available in three to five years.

SHAPIRO: Wild. OK. Next, Marge, can we go to your story about menopause in whales?

CIRINO: Yes, we can. But first, did you know most animals don't go through menopause? Humans are kind of special that way.

SHAPIRO: Not to brag, but I did know that.

CIRINO: Well, I didn't, and so I had Sam Ellis, an animal behavior researcher involved in the study, explain why it's so rare.

SAM ELLIS: The best way to propagate your genes is to get as many offspring as possible into the next generation. The best way to do that is almost always going to be to reproduce for your whole life. So I think really, it's not a surprise that it's so rare because it's such a strange strategy.

KWONG: Sam is at the University of Exeter in the U.K., and he studies menopause in one of the only types of mammals that experience it other than humans, and that is toothed whales like killer whales.

SHAPIRO: So why would these toothed whales experience menopause and not, like, I don't know, baleen whales?

CIRINO: Researchers aren't sure why exactly, but they do know menopause has evolved several times in whales, so they think it must have some benefit.

KWONG: OK. This is the study. It was in the journal Nature. Sam and his team compared the five known species of toothed whales that go through menopause to the ones that don't, and they found that the female whales undergoing menopause lived, on average, 40 years longer than females of other species.

SHAPIRO: Wow.

KWONG: And on top of that, they also lived longer than the males of their own species.

SHAPIRO: And could they say why menopause appears to have this link with longevity?

CIRINO: Well, Sam told me this has to do with something called reproductive competition. Like if a mother and her daughter are both reproducing, you know, still living in the same group at the same time, they're gunning for the same resources, like food. Menopause fixes that. Instead of grandmother whales competing with their daughters for resources, this allows older female toothed whales to provide intergenerational help.

KWONG: Yeah. These grandma whales, they can share food with relatives, share their knowledge of the ecosystem and even babysit their grand-offspring.

SHAPIRO: Wow.

KWONG: Older whales have been documented babysitting their grand-calves.

SHAPIRO: I don't want to anthropomorphize whales, but does this study tell us anything about why menopause may have evolved in humans?

KWONG: That's a good question, yeah.

CIRINO: Yeah. I mean, we can't say for sure that this is why menopause has evolved in humans, but Sam says that's likely the case, and either way, this research reveals some of the social utility of going through menopause and being a grandma.

SHAPIRO: We all love grandmas.

KWONG: Shout-out to the grandmas.

SHAPIRO: OK. Third science story for today is about the secret places songbirds rest during their migration. What a seasonally appropriate choice.

KWONG: Indeed, yes. Happy spring to you, Ari, to everyone. The spring bird migration is underway. That means billions of birds will be migrating north to and through the U.S.

CIRINO: And some of these birds are traveling thousands of miles to breeding grounds in search of food. So scientists generally know where birds are traveling to and from, but what's been less clear is where they stop to rest and recuperate along the way.

SHAPIRO: Secret bird rest stops.

CIRINO: Exactly.

KWONG: Not knowing the rest stops is a problem. It's been kind of the missing link for people who want to protect migrating birds. And bird populations in North America have been plummeting in recent years. Ornithologists estimate roughly 3 billion birds, which is nearly 30% of their population, have been lost in the last 50 years.

SHAPIRO: Oh, so if you want to protect these bird populations, knowing where they rest can help you protect those spaces and protect the populations.

CIRINO: That's right. So a recent study published in Current Biology has finally given us an idea of where this happens along the Eastern U.S. by using weather radar. Our colleague Nathan Rott talked to the lead researcher on the paper, a Princeton Ph.D. student, Fengyi Guo.

FENGYI GUO: The cool thing about this is that most of them are nocturnal migrants, meaning that they migrate at night and they usually take off in a very synchronized way near sunset, which can be well-captured by weather radars.

CIRINO: So birds show up differently on weather radar than rain, for example, and it's those distinctions that help them map out where the birds are resting.

SHAPIRO: I'm dying to know. What were these secret places that the scientists uncovered?

KWONG: So for spring migration, the researchers identified hotspots throughout the Midwest and the East. They're mainly in deciduous forest fragments, so, like, blocks of forest, and when you add up both spring and fall hotspots, the researchers found that only one-third of those spots are in protected areas, like a state forest or a national park.

CIRINO: Fengyi says part of the reason for that is that a lot of this land is privately owned, so she hopes this kind of data can create opportunities to partner up with private landowners on bird conservation efforts.

SHAPIRO: Fascinating.

KWONG: Ari, thank you so much for hanging out with us.

SHAPIRO: It's such a delight. Thanks for having me.

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CIRINO: You can also catch Ari on Consider This, NPR's afternoon news podcast.

KWONG: And before we head out, a quick shout-out to our SHORT WAVE+ listeners. We appreciate you, and we thank you for being a subscriber. SHORT WAVE+ helps support our show, and if you're a regular listener, we'd love for you to join so you can enjoy the show without sponsor interruptions. Find out more at plus.npr.org/shortwave.

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CIRINO: This episode was produced by Gus Contreras and Rebecca Ramirez. It was edited by Rebecca, Viet Le and Christopher Intagliata.

KWONG: Rebecca and Rachel Carlson checked the facts, and the audio engineers were Kwesi Lee and Ko Takasugi-Czernowin. I'm Emily Kwong.

CIRINO: I'm Margaret Cirino.

KWONG: Thanks for listening to SHORT WAVE from NPR.

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