The Haenyeo’s diving prowess didn’t come down to genetics alone. The study also found that the female divers had a slower heart rate than non-divers during the tests — a factor that would help them to conserve oxygen during a dive.
“It was quite dramatic. Actually, their heart rate dropped about 50% more over the course of the dive than the control (participants). We know that it’s because of training, because it’s something that we only saw in the Haenyeo,” Ilardo said.
Ilardo’s previous work involving free diving communities known as the Bajau in Sulawesi, Indonesia, had revealed genetic adaptations that allowed the Bajau to go for longer periods without oxygen, resulting in unusually large spleens.
However, while Jeju residents did, on average, have a larger spleen than the study participants from mainland South Korea, the effect wasn’t significant when other factors like age, height and weight were accounted for, she said.
A target for new drugs
The genetic variant that the study identified in the Jeju residents associated with lower blood pressure should be explored further, according to Ben Trumble, an associate professor at Arizona State University’s School of Human Evolution and Social Change.
“Those with this gene had more than a 10% reduction in blood pressure compared to those who don’t have this gene, that’s a pretty impressive effect,” said Trumble, who wasn’t involved in the study. “Genes code for proteins, and if we can figure out which changes in proteins impact blood pressure, we could potentially create new drugs,”
Nearly all medical and genetic studies are conducted in industrialized populations, usually in urban city centers, making Ilardo’s approach particularly valuable, Trumble added.
“Almost everything we know about what is ‘normal’ when it comes to health is from these sedentary urban populations. However, for 99.9% of human history, we were hunter-gatherers,” he said.
“Natural selection optimized our bodies under very different selective pressures than those we face today.”
Ilardo said she hopes to continue to study Jeju’s female divers and get a deeper understanding of the medical implications.
“This study raises more questions than it answers, but first and foremost, it shows these women are extraordinary,” she said.
“There’s something biologically different about them that makes them extremely special, no matter how you characterize it, and what they do is unique and worth celebrating.”
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