Sunday, May 04, 2025

The all-female Korean Haenyeo divers show genetic adaptions to cold water diving

Cell Press

Group of Haenyeo divers on a rocky shore — image:
A group of Haenyeo divers in Jeju, Korea.
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Credit: Melissa Ilardo

The Haenyeo, a group of all-female divers from the Korean island of Jeju, are renowned for their ability to dive in frigid waters without the aid of breathing equipment — even while pregnant. A study publishing on May 2 in the Cell Press journal Cell Reports shows that the divers’ remarkable abilities are due to both training and genetic adaptation, including gene variants associated with cold tolerance and decreased blood pressure. The divers also showed pronounced bradycardia, or slowing of the heart rate, when they dived, but this trait is likely due to a lifetime of training, not genetics.

“The Haenyeo are amazing, and their incredible ability is written in their genes,” says geneticist Melissa Ilardo of the University of Utah. “The fact that women are diving through their pregnancy, which is a really tough thing to do, has actually influenced an entire island’s people.”

The Haenyeo, or “women of the sea,” dive year-round in social collectives to harvest food for their communities. They begin training at around age ten and continue for their whole lives. Inspired by the Haenyeo’s remarkable diving abilities, the researchers wanted to know whether they have distinguishable physiological traits that help them cope with the strain of diving, and if so, whether these traits are due to genetic adaptation or training.

To find out, the team compared the physiological traits and genomes of 30 Haenyeo divers to 30 non-Haenyeo people from Jeju, as well as 31 people from mainland Korea. To match the age of the divers, the average age of all participants was 65. The researchers compared the participants’ heart rate and blood pressure at rest and during “simulated dives” where the participants held their breath while submerging their faces in cold water.

“If you hold your breath and put your face in a bowl full of cold water, your body responds as if you’re diving,” says Ilardo. “A lot of the same processes happen in your body that would happen if you were to jump in the ocean, but it’s done in a way that’s safe for people with no diving experience.”

The team’s genomic analysis showed that Jeju residents — both Haenyeo and non-Haenyeo — were distinct from individuals from mainland Korea, suggesting that all Jeju residents are descended from the same ancestral population.

“We can essentially think of everyone from Jeju as either ‘diving Haenyeo’ or ‘non-diving Haenyeo,’ because their genetics are the same,” says Ilardo.

The genomic analysis also revealed two gene variants in the Haenyeo that may help them cope with the pressures of diving, making the Haenyeo the second known population of traditional breath-hold divers that has evolved for diving. One gene is associated with cold tolerance, which could make the divers less vulnerable to hypothermia. The other gene is associated with decreased diastolic blood pressure (i.e., blood pressure in between heart contractions). The variant was found in 33% of participants from Jeju but only 7% of mainland participants.

“This association may reflect natural selection to mitigate the complications of diastolic hypertension experienced by female divers while diving through pregnancy,” says Ilardo. “Since Bajau women also dive while they’re pregnant, we wonder whether pregnancy is actually driving a lot of the genetic changes in these diving populations.”

During the simulated dives, all of the participants showed decreased heart rates, but the Haenyeo’s heart rates dropped significantly more than those of either control group. On average, the divers’ heart rates decreased by 18.8 beats per minute (bpm) compared to a decrease of 12.6 bpm in the Jeju non-divers. A lowered heart rate during diving is beneficial because it saves energy and conserves oxygen. Since their genomic analysis indicated that Haenyeo and non-diving Jeju are genetically members of the same population, the researchers concluded that this feature is likely due to the divers’ training.

“Because the Haenyeo have been diving for a very long time, their heart rate has been trained to drop more,” says Ilardo. “This was something we could actually visually see — we had one diver whose heart rate dropped by over 40 beats per minute in less than 15 seconds.”

The researchers say that these findings highlight the potential of studying traditional diving populations to better understand human genetic and physiological adaptation.

“We’re really excited to learn more about how these genetic changes may be affecting the health of the broader population of Jeju,” says Ilardo. “If we can more deeply characterize how those changes affect physiology, it could inspire the development of therapeutics to treat different conditions, such as hypertensive disorders of pregnancy and stroke.”

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This research was supported by the Office of Naval Research, the National Institutes of Health, and the National Science Foundation.

Cell Reports, Aguilar-Gómez et al., “Genetic and training adaptations in the Haenyeo divers of Jeju, Korea.” https://www.cell.com/cell-reports/fulltext/S2211-1247(25)00348-1

Cell Reports (@CellReports), published by Cell Press, is a weekly open-access journal that publishes high-quality papers across the entire life sciences spectrum. The journal features reports, articles, and resources that provide new biological insights, are thought-provoking, and/or are examples of cutting-edge research. Visit http://www.cell.com/cell-reports. To receive Cell Press media alerts, contact press@cell.com.

A Haenyeo diver carries a net full of seafood on her back while walking along a rocky shoreline in Jeju, Korea.

Haenyeo divers on a fishing boat off the coast of Jeju, Korea preparing for a dive.

Credit

Ho-Joon Lee

Journal

Cell Reports

DOI

10.1016/j.celrep.2025.115577

Method of Research

Experimental study

Subject of Research

People

Article Title

Genetic and Training Adaptations in the Haenyeo Divers of Jeju, Korea

Article Publication Date

2-May-2025

“It’s like they have a superpower”: Genetic analysis of all-women extreme divers finds changes linked to blood pressure, cold tolerance

University of Utah Health

Haenyeo wave — image:
A Haenyeo diver at the water's edge. Divers spend hours in the water, every day, lifelong.
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Credit: Diana Aguilar-Gómez

A new analysis of a group of all-women extreme divers off the coast of Korea has uncovered genetic differences that could help them survive the intense physiological stresses of free-diving—and could ultimately lead to better treatments for blood pressure disorders.

The results are published in Cell Reports.

The researchers worked with the Haenyeo: women who have spent their whole lives diving in the waters off Jeju Island, 50 miles south of mainland South Korea. They free-dive up to 60 feet below the surface to harvest seaweed, abalone, and other food items from the seafloor, spending hours a day in the water all year round. For hundreds of years, Haenyeo diving was a staple of Jeju’s economy and culture, although the practice is now waning. Today, most divers are in their 60s and 70s.

“They’re absolutely extraordinary women,” says Melissa Ilardo, PhD, assistant professor of biomedical informatics at University of Utah Health and the senior author on the study. “Every day, they head out and get in the water, and that’s where they work all day. I saw women over 80 diving off a boat before it even stopped moving.”

To figure out if the Haenyeo’s diving abilities are aided by differences in genetics, the researchers measured physiological variables related to diving ability, such as blood pressure and heart rate. They then sequenced participants’ DNA—and found two changes related to diving physiology that could give the Haenyeo advantages underwater.

Adapting to a high-pressure environment

Haenyeo divers are more than four times more likely than mainland Koreans to have a genetic change associated with lower blood pressure while diving. The researchers believe this difference could keep divers and their unborn children safe when diving during pregnancy.

Breath-hold diving not only limits the body’s oxygen supply but also raises divers’ blood pressure during a dive, the researchers say. Holding one’s breath in other contexts, such as sleep apnea, is associated with pregnancy-related blood pressure disorders, although it’s unknown whether diving causes the same effect.

The researchers speculate that if the genetic change helps lower blood pressure, it could be especially vital for the Haenyeo. These women dive throughout pregnancy and must avoid blood pressure conditions such as preeclampsia, which can be fatal. “This is not something that every human or every woman is able to do,” says Diana Aguilar-Gómez, PhD, postdoctoral researcher in evolutionary biology at University of California, Los Angeles, and the first author on the study. “It’s kind of like they have a superpower.”

Cold comfort

A second genetic difference is related to pain tolerance—specifically, cold-based pain. Air temperatures off Jeju Island drop to around freezing in the winter, but the Haenyeo don’t stop diving. “I asked them once if they would stop diving if it got cold enough,” Ilardo says. “They said that as long as the wind alarm doesn’t go off, they’ll still get in the water.” She clarifies, “The wind alarm is to keep them from blowing out to sea.”

The team didn’t measure individuals’ cold tolerance, so they can’t say whether the change they see may be important for the Haenyeo’s ability to dive year-round. But they plan to investigate the difference further in future work.

The genetic differences that could boost diving ability are found throughout the population of Jeju Island. But much of what makes the Haenyeo women special comes from a lifetime of practice. Researchers have long known that when anyone dives—trained or untrained, Haenyeo or not—their heart rate reflexively drops to conserve oxygen for longer. For an average untrained person from Jeju Island, heartbeat slows down by about 20 beats per minute over the course of a simulated dive. For Haenyeo with a lifetime of diving experience, heart rate drops by up to twice that.

Advancing health for all

The researchers hope that their discovery of a genetic difference linked to blood pressure will ultimately advance care for health conditions, like stroke, that are related to high blood pressure.

Intriguingly, Jeju Island has one of the lowest rates of stroke mortality in Korea, raising the possibility that the genetic change could help protect against stroke, Ilardo says. “If there’s something about it that actually reduces the risk of stroke mortality, then we could help people everywhere by understanding what’s special about these women.”

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This research is published in Cell Reports as “Genetic and Training Adaptations in the Haenyeo Divers of Jeju, Korea.”

This research was supported by the Office of Naval Research (N00014-20-1-2556), the National Institute of Health (NIGMS R35GM153400, NHGRI R00HG011658), the National Science Foundation (Graduate Research Fellowship 2146752), the UC MEXUS-CONACYT Doctoral Fellowship, and the Fulbright-García Robles.

Content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.