What Makes South Korea's 'Super Divers' Special?

For generations, the all-female Haenyeo divers have routinely dove into frigid waters off the coast of South Korea, holding their breath for minutes at a time, as they collect seafood to eat and sell. These women start diving as girls and continue well into old age. And recent research suggests that it's not just years of training that makes this feat possible – it's also a set of special genetic adaptations. Science reporter Ari Daniel https://www.npr.org/people/297147967/ari-daniel brings us the story. Read more of Ari's reporting here https://www.npr.org/sections/shots-health-news/2025/05/15/nx-s1-5381139/korean-haenyeo-female-free-divers-genes-adaptations-jeju. Have another story about biology and genetics for us to consider? Email us at [email protected] mailto:[email protected]. Listen to every episode of Short Wave sponsor-free and support our work at NPR by signing up for Short Wave+ at plus.npr.org/shortwave http://plus.npr.org/shortwave. See pcm.adswizz.com https://pcm.adswizz.com for information about our collection and use of personal data for sponsorship and to manage your podcast sponsorship preferences. NPR Privacy Policy https://www.npr.org/about-npr/179878450/privacy-policy

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• 0:00Speaker 00

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• 0:16Emily Kwong?

  You're listening to Short Wave from NPR. Hey, everybody. It's Emily Kwong, and I am with science reporter Ari Daniel. You're taking us on an adventure today, right, Ari?

• 0:28Speaker 02

  I am indeed. Emily, I'm going to take you to Jeju Island.

• 0:32Emily Kwong?

  Ooh. Where's Jeju Island?

• 0:34Speaker 02

  It's like 50, 60 miles off the coast of South Korea. And in this video that you're hearing, there's a motorboat that's chugging along the coast. Before the vessel even comes to a stop, an older woman in a wet suit jumps into the water and dives down.

• 0:52Emily Kwong?

  Oh, so this is a diver?

• 0:53Speaker 02

  Yeah.

• 0:54Emily Kwong?

  Cool. Wet suit, I'm assuming she's also got fins and a mask?

• 0:57Speaker 02

  Yes, yep, yes.

• 0:58Emily Kwong?

  And like an oxygen tank and stuff?

• 1:00Speaker 02

  No, just pure lung capacity. This woman is part of a long line of female freedivers on Jeju Island called the Haenyeo.

• 1:09Emily Kwong?

  Oh.

• 1:10Speaker 02

  And these women can hold their breath a really long time, Emily. Up to two or three minutes.

• 1:17Emily Kwong?

  Two to three minutes?

• 1:19Speaker 02

  Minutes.

• 1:20Emily Kwong?

  What are the Haenyeo doing down there?

• 1:21Speaker 02

  They're collecting all kinds of seafood to eat and sell.

• 1:25Speaker 03

  Things like abalone, sea urchins, you know, harvest seaweed sometimes.

• 1:30Emily Kwong?

  It's like grocery shopping while holding your breath.

• 1:32Speaker 02

  Marine grocery shopping, exactly.

• 1:34Emily Kwong?

  Yeah.

• 1:34Speaker 02

  This is Melissa Alardo. She's an evolutionary geneticist at the University of Utah. And she sent me this video that she took of a few Haenyeo divers who routinely dive in waters that can be in the 50-degree range.

• 1:49Emily Kwong?

  Oh, so they're diving in really cold water?

• 1:51Speaker 02

  Yeah, I could never do it. I mean, I can barely handle 70-degree water. But these women, they start diving as girls and continue well into old age. And what's astonishing is that it's not just years of training that make this feat possible. It's also a set of special adaptations, ones that Melissa and her team recently uncovered.

• 2:13Emily Kwong?

  So today on the show, the super divers of Jeju Island.

• 2:16Speaker 02

  Plus, the mix of physiological and genetic adaptations that make these women's dives possible.

• 2:23Emily Kwong?

  I'm Emily Kwong.

• 2:24Speaker 02

  And I'm Ari Daniel.

• 2:25Emily Kwong?

  And you're listening to Short Wave from NPR.

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• 3:50Emily Kwong?

  So, all right, today we're talking about the Hennyo, these female freedivers in South Korea. How do the Hennyo compare to other freedivers around the world? What makes their abilities so special?

• 4:03Speaker 02

  I mean, freediving anywhere is tough, Emily, but the conditions that the Hennyo are operating under are pretty extreme.

• 4:10Speaker 03

  One of the first times I was there, it was snowing. They said, as long as there's not a risk that they're going to be blown away to sea, then they still go out in the water, no matter how cold it is.

• 4:19Emily Kwong?

  That's commitment.

• 4:20Speaker 02

  Indeed. And these women dive across all of life's milestones, which I talked to Melissa and her collaborator, Diana Aguilar Gomez, about. Diana is a population geneticist currently at UCLA.

• 4:33Speaker 05

  Throughout their whole pregnancy, they say they just dive until basically before they give birth.

• 4:40Speaker 03

  And then they were back in the water three days later.

• 4:42Speaker 05

  Yeah, it's amazing.

• 4:43Speaker 02

  Deanna and Melissa wanted to know whether there were adaptations the Heno might have that allow them to do this, and they recently pinpointed some in a study that published in the journal Cell Reports.

• 4:57Emily Kwong?

  Fascinating. Okay, how did that study come about?

• 5:00Speaker 02

  Well, Melissa Ilardo, she runs something called the Superhuman Lab, where she studies extreme physiologies across different populations, including among the Bajau freedivers in Indonesia.

• 5:12Speaker 03

  They're just really good at holding their breath and being underwater. And we found that the Bajau had larger spleens, and we were able to link this to a genetic adaptation. And so the spleen plays a role in diving because it stores red blood cells that are oxygenated. And when you dive, your spleen contracts, and it pushes those red blood cells into circulation. So essentially, we think the Bajau have big spleens because it enables them to stay underwater longer.

• 5:38Speaker 02

  Melissa told me the Bajau were the first group of people that were found to have evolutionary adaptations to make this kind of diving safer. And she wanted to know how the Heno might be adapted to their extreme lifestyle.

• 5:52Speaker 03

  How evolution might have shaped the Heno to be better divers, to dive more safely, to dive for longer.

• 5:58Emily Kwong?

  Yeah, it's so impressive that they can do this. So how did Melissa and her team go about conducting this study?

• 6:03Speaker 02

  Well, they decided to compare the Heno to other elderly women on the island who aren't divers but have a similar genetic background, and to still others off-island who aren't related, about 30 women in each group.

• 6:15Emily Kwong?

  Okay, so they had some groups of non-divers to compare to the divers. So how did they compare them? Because I assume they didn't just throw all these elderly women into the open ocean and hope for the best.

• 6:28Speaker 02

  They certainly did not try that approach.

• 6:31Emily Kwong?

  Oh, good.

• 6:31Speaker 02

  Fortunately, there's a workaround, a safer workaround. It's called simulated dive.

• 6:37Speaker 03

  You hold your breath and put your face in a bowl full of cold water, and your body responds as if you're diving. Your heart Will drop measurably.

• 6:45Emily Kwong?

  Hmm, I've done this when I'm very anxious. But why does your heart rate drop when you put your head in a bowl of ice water?

• 6:52Speaker 02

  It's just an automatic thing, Emily. Your body acts like it's underwater and triggers something that's called the mammalian diving reflex, which slows down your heart rate, allowing it to do less work to limit oxygen consumption. The Hengyo, though, they found this experiment kind of silly.

• 7:12Speaker 03

  They said like getting in the ocean, being underwater, that's diving. Whatever this is, this isn't diving. But they still held their breath long enough that we were able to elicit a response.

• 7:21Emily Kwong?

  I'm just picturing all these aunties and grandmas like, oh, for science, I guess if I have to, but. So what was the response between the Hengyo and the non-divers in doing this?

• 7:32Speaker 02

  There was a significant one. The Hengyo heart rate fell by about 50% more than their non-diving peers.

• 7:40Emily Kwong?

  Wow.

• 7:40Speaker 03

  We had one diver whose heart rate dropped over 40 beats per minute in 15 seconds.

• 7:45Speaker 02

  Melissa says the Hengyo response is due to a lifetime of training and diving experience. So it's classic physiological adaptation.

• 7:54Emily Kwong?

  What about genetic adaptation? Did they do an analysis of those women on the level of their DNA as well?

• 8:01Speaker 02

  They did. The researchers took saliva samples to look for genetic differences between the three groups. And they found that everyone from Jeju, both the divers and the non-divers, had basically the same genes, meaning that the people of the island appear to have been genetically sculpted by generations of divers.

• 8:22Speaker 03

  What this suggests is that everybody in Jeju has an equally likely chance of being a descendant of a diver.

• 8:29Emily Kwong?

  What a thing to inherit. And was there anything special about this particular gene pool that stood out?

• 8:35Speaker 02

  Yeah, two things, actually. The first was a gene that seems to be related to cold tolerance.

• 8:41Speaker 03

  Maybe that protects them from hypothermia in ways that we don't fully understand yet.

• 8:45Emily Kwong?

  That makes sense.

• 8:46Speaker 02

  Right. And the second gene is associated with blood pressure, which Diana Aguilar Gomez, who did this work as a PhD student at UC Berkeley, thinks is likely connected to blood vessel structure and function.

• 8:59Speaker 05

  Diving increases your blood pressure, and particularly through pregnancy, that can be very dangerous. It can increase your risk for preeclampsia.

• 9:08Speaker 02

  So if these women have a gene that lowers their blood pressure, it's like built-in protection from preeclampsia and other life-threatening complications. And so...

• 9:19Speaker 05

  Probably women that would protect it against this would be more likely to have more children.

• 9:25Emily Kwong?

  Oh, and they would pass those genes along.

• 9:29Speaker 02

  Bingo. And I should tell you, Emily, that Jeju Island has an especially low rate of stroke mortality. And Melissa thinks that could be related to this second protective gene, since stroke can result from high blood pressure.

• 9:43Speaker 03

  Wouldn't it be amazing if, by studying divers in Korea, we can translate these findings to develop a therapeutic that protects people from stroke around the world? So by studying these populations, it can lead to discoveries that could have really important implications for people everywhere.

• 9:59Emily Kwong?

  Absolutely. This is so the value of studying outliers. So what health lessons can be learned from these freedivers?

• 10:05Speaker 02

  So I spoke with Stephen Chung, who studies extreme physiology at Brock University in Canada. He wasn't involved in the research, but he addressed this exact question.

• 10:15Speaker 06

  By pushing the body to its limits, we get a better sense of where those limits are, but also just what the human body is capable of.

• 10:25Speaker 05

  I'm not even near the age of these women, and I don't think I can go and dive all day. I mean, I feel like that's like a superpower.

• 10:34Speaker 02

  A superpower that Deanna says may not be around for much longer.

• 10:39Speaker 05

  The newer generations of women, they're like going to university and doing other stuff. So like, the average age of the Haenyeo nowadays is around 70 years old.

• 10:49Emily Kwong?

  Oh, wow. So this is just becoming an increasingly rare practice, even if the genetics live on in the descendants of these divers.

• 10:57Speaker 02

  That's true. And it's one of the reasons that it was important to Melissa that her and her team returned to Jeju Island to share their results with the Haenyeo.

• 11:08Speaker 03

  These women are extraordinary. Their biology is amazing, and what they do is amazing. And so I think it's really important to celebrate just how unique these women are and how it's changed their bodies and the bodies of other people on this island.

• 11:20Emily Kwong?

  Ari Daniel, thank you so much for coming on Short Wave. I'm really glad we know more about the Hanyo.

• 11:25Speaker 02

  Thanks for having me, Emily. I love being here.

• 11:28Emily Kwong?

  If you liked this episode of Short Wave and you want to support the show, follow us on the NPR app or wherever you get your podcasts, and you'll never miss an episode. This episode was produced by Hannah Chin, it was edited by our showrunner Rebecca Ramirez, and fact-checked by Tyler Jones. Jimmy Keely was the audio engineer. Beth Donovan is our senior director, and Colin Campbell is our senior vice president of podcasting strategy. I'm Emily Kwong. Thank you for listening to Short Wave from NPR.

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