Just off South Korea’s southern coast lies Jeju Island, home to a community of women divers known as Haenyeo, or “women of the sea.” These women are trained at a young age in free diving into the frigid sea to harvest shellfish, even while pregnant. As Tibetans adapted to high altitudes and Bajau divers developed underwater endurance, researchers wondered if generations of diving shaped Haenyeo physiology through training, genetics, or both.1,2
Haenyeo divers on a fishing boat off the coast of Jeju, South Korea, preparing for a dive.
Ho-Joon Lee
Published in Cell Reports, a team of researchers found two gene variants associated with cold tolerance and decreased blood pressure that likely aid Haenyeo while diving.3 These findings will help researchers better understand human genetic and physiological adaptation, especially within a traditional diving population.
First, the team assessed physiological traits related to diving in women from three populations: Haenyeo in Jeju, non-Haenyeo in Jeju, and non-Haenyeo from mainland South Korea. The researchers compared the participants’ heart rate and blood pressure at rest and during simulated dives, in which all women 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,” explained geneticist Melissa Ilardo of the University of Utah in a press release. A lowered heart rate during diving is beneficial because it saves energy and conserves oxygen.
Among these groups, the Haenyeo had a significant decrease in heart rate during these simulated dives, despite the short dive time. “Because the Haenyeo have been diving for a very long time, their heart rate has been trained to drop more,” explained Ilardo. Heart rates in Jeju non-divers slowed to about 20 beats per minute but dropped even further for Haenyeo. “We had one diver whose heart rate dropped by over 40 beats per minute in less than 15 seconds.”
Then, the researchers conducted genomic analysis to identify genes or variants that may benefit Haenyeo. They found two notable gene variants that may help the women cope with the pressures of diving. One is associated with cold tolerance, potentially protecting them from hypothermia during frigid dives. The other, linked to lower diastolic blood pressure, appeared in 33 percent of all Jeju participants but was only seen in seven percent of mainlanders. Because elevated diastolic blood pressure has been linked to pregnancy risk factors, researchers believe that this variant may reflect recent natural selection to mitigate health risks for women diving throughout their pregnancy.4
These genetic traits, with rigorous training, are likely to contribute to the Haenyeo's diving skills. “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,” said Ilardo.
- Yi X, et al. Sequencing of 50 human exomes reveals adaptation to high altitude. Science. 2010;329(5987):75-78.
- Ilardo MA, et al. Physiological and genetic adaptations to diving in sea nomads. Cell. 2018;173(3):569-580.e15.
- Aguilar-Gómez, et al. Genetic and training adaptations in the Haenyeo divers of Jeju, Korea. Cell Reports. 2025:115577.
- Nørgaard SK, et al. Diastolic blood pressure is a potentially modifiable risk factor for preeclampsia in women with pre-existing diabetes. Diabetes Res Clin Pract. 2018;138:229-237.
