In the coastal waters of Southeast Asia lives a remarkable group of people who have adapted in an extraordinary way to life at sea.
Known as the Bajau, or “Sea Nomads,” this tribe has spent nearly a millennium living in close connection with the ocean, so much so that they often reside in stilted houses over the water, spending the majority of their days diving, fishing, and foraging beneath the surface, captured by photographers across the globe like Rehahn Photographer.
For generations, the Bajau have relied on traditional free-diving techniques to gather food, spearfishing and collecting shellfish with impressive skill. Now, science has uncovered a fascinating biological adaptation that may explain how they manage such a demanding aquatic lifestyle.
Researchers studying the Bajau discovered that they possess significantly larger spleens than neighboring populations. While the spleen is not commonly associated with diving ability, it plays a key role in oxygen storage, per the National Geographic. When the body is submerged in water and oxygen is scarce, the spleen contracts and releases oxygen-rich red blood cells into circulation, a natural boost that can extend breath-holding capacity.
“It’s like a biological scuba tank,” explained Melissa Ilardo, lead author of the study from the University of Copenhagen, in an interview with BBC’s Inside Science.
The Bajau’s spleens were found to be 50% larger on average than those of nearby villagers who do not dive regularly.
Ilardo described the tribe’s daily routine: diving for up to eight hours a day, often to depths of over 70 meters, using traditional wooden goggles and weighted belts. At any given moment, they spend around 60% of their time underwater, with dives lasting anywhere from 30 seconds to several minutes.
This extreme lifestyle triggers the human dive response, a set of physiological reactions that slow the heart rate, restrict blood flow to the limbs, and squeeze the spleen to release oxygen.
Over generations, the Bajau appear to have evolved to enhance this response.
The study didn’t just stop at physiology, it uncovered a genetic basis for this adaptation. Researchers found that the PDE10A gene, which regulates thyroid hormones in mice and influences spleen size, was far more common in the Bajau population.
“We asked whether any genetic variants are more frequent in the Bajau compared to others,” said co-author Prof. Rasmus Nielsen from UC Berkeley, via BBC News. “PDE10A stood out.”
This discovery echoes findings from other high-adaptation communities, such as Tibetans living at high altitudes, who carry genetic traits believed to be inherited from Neanderthals, leading scientists to wonder if similar ancient interbreeding could have influenced the Bajau’s evolution.
Despite their extraordinary adaptation, the Bajau way of life is increasingly at risk. Santarawi Lalisan, a tribal elder, shared concerns about how pollution, especially plastic, is a growing threat, according to Science Times.
As pollution, modernization, and climate change threaten their environment, the future of the Bajau’s ocean-based culture remains uncertain.
Still, their story is a striking example of how humans can biologically adapt to even the most extreme conditions.