For hundreds of years, a remarkable group of women on South Korea’s Jeju Island has made a living by diving deep into the ocean without oxygen tanks.
Known as the Haenyeo, or “women of the sea,” they collect seafood such as abalone, sea cucumbers, shellfish, and seaweed from the seabed.
Their work is physically demanding and often dangerous. They can dive as deep as 20 meters, stay underwater for long periods while holding their breath, and repeat these dives many times each day.
They continue working through cold winters, rough seas, and strong ocean currents. Even more impressive, many of today’s Haenyeo are in their 60s, 70s, and even 80s, yet they continue diving regularly.
For a long time, scientists believed their amazing abilities were mainly the result of years of training and experience. Like athletes, the Haenyeo spend their entire lives developing the strength, breathing control, and endurance needed for free diving.
However, a new study suggests there may be another important reason behind their extraordinary abilities. Researchers have found evidence that some people on Jeju Island carry genetic changes that may help them cope with the extreme demands of diving.
The research was led by Melissa Ilardo from the University of Utah. Her team studied the Haenyeo by measuring their heart rate, blood pressure, and DNA.
They also compared their results with people living on mainland South Korea. The scientists discovered two genetic differences that appear to be much more common among people from Jeju Island.
One of the most important discoveries involved blood pressure. Normally, when people hold their breath underwater, the body’s natural diving response causes blood pressure to rise.
This helps direct oxygen-rich blood to important organs such as the brain and heart. Although this response is useful, blood pressure that becomes too high can also increase health risks, especially for people with heart disease or during pregnancy.
The researchers found that many Haenyeo carry a genetic variation that appears to help keep blood pressure from rising too much during diving. People on Jeju Island were more than four times as likely to carry this gene variation compared with people living on the mainland.
This finding may explain why generations of Haenyeo have been able to continue diving safely, including some women who traditionally dived while pregnant.
High blood pressure during pregnancy can lead to a dangerous condition called preeclampsia, so understanding how this genetic change works could eventually help researchers develop better treatments for people with high blood pressure.
The second genetic difference was linked to the way the body responds to cold. Jeju Island’s coastal waters become very cold during winter, yet the Haenyeo continue diving throughout the year unless weather conditions become too dangerous.
The researchers identified a gene connected with cold pain, suggesting that people from Jeju Island may experience cold differently. Although the study did not directly measure pain tolerance, the finding may help explain how the Haenyeo can spend so much time in freezing seawater.
Genes are only part of the explanation. The researchers found that lifelong training has a major effect on the body’s diving response. All humans have a natural diving reflex. When a person holds their breath and puts their face in water, the heart slows down to save oxygen. In most people, the heart rate drops by around 20 beats each minute.
Among the Haenyeo, however, the heart slowed by roughly twice that amount. This stronger response appears to develop through decades of repeated diving, showing that experience is just as important as genetics.
Interestingly, the genetic changes are not found only in the Haenyeo. Many people living on Jeju Island also carry them, even if they do not dive. This suggests that these traits became common in the local population over many generations, while the demanding lifestyle of the Haenyeo allowed these natural advantages to become especially valuable.
The findings could have important medical benefits beyond understanding human adaptation. High blood pressure is one of the leading causes of heart disease and stroke around the world.
Scientists believe that learning how the Jeju gene helps control blood pressure may eventually lead to new treatments. Researchers have also noted that Jeju Island has one of the lowest stroke death rates in South Korea, raising the possibility that these genetic differences may contribute to better heart health in the local population.
More research will be needed before these discoveries can be turned into medical treatments. Scientists must first understand exactly how these genes work and whether similar effects can be safely reproduced in other people. Even so, the study provides a fascinating example of how the human body can adapt over many generations to a unique way of life.
The research was published in the journal Cell Reports. It not only tells the story of the remarkable Haenyeo women but also opens a new path for studying blood pressure, cold tolerance, and human health.
What began as an investigation into one of the world’s most extraordinary diving traditions may one day help scientists develop new ways to protect millions of people from heart disease and stroke.
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