For many generations, the Bajau have used traditional free-diving methods to survive, relying on their incredible skill to spear fish and collect shellfish deep underwater. But recently, scientists have discovered something remarkable about their biology that might explain how they’re able to handle such a physically intense lifestyle in the sea.It turns out that the Bajau have significantly larger spleens compared to nearby groups who don’t spend as much time underwater. Even though the spleen isn’t something most people associate with diving, it actually plays a crucial role in helping the body store and release oxygen. According to National Geographic, when a person dives and oxygen becomes limited, the spleen contracts and pushes oxygen-rich red blood cells into the bloodstream, giving a boost that helps with holding your breath for longer.
“It’s like a biological scuba tank.” said Melissa Ilardo, a researcher at the University of Copenhagen who led the study. She shared these insights during an interview with BBC’s Inside Science.
On average, the Bajau were found to have spleens that are 50% larger than those of nearby villagers who don’t dive daily.Ilardo explained that these sea nomads spend long hours up to eight per day—diving to depths that can go beyond 70 meters. They use simple gear like handmade wooden goggles and weighted belts. At any given time, they’re underwater for about 60% of their daily routine. Some of their dives last just half a minute, while others stretch on for several minutes.
This intense routine activates what’s known as the human dive response. It’s a series of automatic body changes that help conserve oxygen by slowing the heart rate, limiting blood flow to certain parts of the body, and triggering the spleen to release more oxygen-rich blood.
Over hundreds of years, it looks like the Bajau have physically evolved to make the most out of these natural diving reflexes.And the research didn’t just focus on body function—it went deeper into their genetics. Scientists discovered a specific gene called PDE10A that influences the size of the spleen. This gene helps control thyroid hormones in mice, and it seems to be much more common among the Bajau compared to other groups nearby.
“We asked whether any genetic variants are more frequent in the Bajau compared to others.” said Professor Rasmus Nielsen, a co-author of the study from UC Berkeley, speaking to BBC News. “PDE10A stood out.”
