Diving Into The Genetic Adaptations of Sea Nomads

We humans are incredibly adaptable, and the evidence for that is in our DNA.

We have survived and thrived around the world, even in extreme environments, not just because of our intelligence and culture, but because of our biology.

Early this year, a study of the Bajau — an ethnic Malay people who for a thousand years have lived in and around the ocean as so-called “Sea Nomads” — offers the latest example of how genetic adaptations have given some populations the advantage they need to survive.

The Bajau’s life at sea — spending hours diving for fish — created evolutionary pressure that favored a trait allowing them to hold their breath longer and dive deeper. Those who did not have that trait, researchers speculate, didn’t survive.

The average person can hold their breath underwater for about a minute or two. With a little practice, a person can learn to push their underwater time to several minutes. But the research that was done by Melissa Ilardo, a University of Copenhagen, Ph.D. student, found that genetics also plays a role in their ability to dive longer and deeper than most people.

Bajau people have on average spleens that are 50 percent larger than other people of the same ethnic group, according to the research done by Ilardo. During a dive, the spleen contracts and this pushes out oxygen-rich blood into the circulatory system while they are holding their breath. The research found that there was a variant in the gene PDE104, which controls thyroid hormone and can lead to larger spleens. This variant was often found to appear in Bajau people.

The study parallels research of evolutionary advantages among other populations in extreme environments around the globe.

For example, researchers have found a genetic adaptation among Tibetans who live at high altitudes where the level of oxygen is lower than at sea level. Tibetans were more likely to have variants on the EPAS1 gene that prevents blood thickening, a genetic advantage, and that this genetic advantage is something that was likely inherited from an ancient human cousin, the Denisovans, more than 40,000 years ago.

Interestingly, the Denisovans may have also contributed to the genetic adaptation that has helped the Bajau. Along with the variants that influence spleen size among Bajau, researchers also found variants in higher frequency among the Bajau in the gene FAM178B, which is involved in helping the body maintain the proper pH balance in the blood, and is believed to have come from Denisovans.

The genetic research done among the Bajau and Tibetans points to the value of studying isolated populations who may provide valuable insights not just into human evolution but to the possible treatment of certain conditions that affect us all.