The Bajau, Southeast Asia’s sea nomads, have captured the world’s attention with their extraordinary underwater abilities, which allow them to dive deep and stay submerged for an extensive duration, catching marine life by hand. These astonishing capabilities are the result of a rare genetic adaptation that has seen the Bajau evolve significantly larger spleens, providing a natural reservoir of oxygenated blood that enables them to hold their breath for up to 13 minutes underwater.
Researcher Melissa Ann Ilardo, driven by a profound curiosity about the Bajau’s diving prowess, embarked on a pioneering journey that would uncover the secrets of their unique physiology. “I heard that they had extraordinary diving abilities,” said Ilardo, an evolutionary geneticist. “I thought it seemed like a really interesting opportunity to study natural selection.” Her exploration into the lives of the Bajau, who spend a remarkable 60 percent of their daily life beneath the waves, led to groundbreaking findings on human adaptation.
Ilardo’s hypothesis centered on the spleen, an organ known to aid diving mammals like seals by contracting during dives to release a boost of oxygenated red blood cells into the bloodstream. The Bajau, she theorized, might have developed a similar physiological trait, and her research, involving ultrasound measurements and DNA sampling, confirmed it. “They were a little puzzled by the ultrasound machine and by this weird question of they might have bigger spleens,” Ilardo commented on her unique home visits. “But they were curious themselves to find out if that was true.”
Her hunch was right: the Bajau’s spleens were found to be 50 percent larger compared to their land-dwelling neighbors, the Saluan people, and even among the Bajau who did not actively dive. Further genetic analysis highlighted the PDE10A gene variant, associated with thyroid hormone levels and implicated in spleen growth.
These findings not only documented a remarkable example of human adaptation but also challenged the very nature of human evolution. Ilardo noted, “But what we see in the Bajau, they’re imposing these conditions on themselves, they’re creating an environment that is causing them to evolve.” This evolution has enabled the Bajau to continue their traditional spearfishing practices, relying on minimal diving gear such as weight belts and wooden masks.
The Bajau’s adaptation, unique among human populations, adds to our understanding of how human physiology can evolve in response to environmental pressures. The study of their enlarged spleens has implications beyond anthropology; it may provide insights into medical conditions associated with hypoxia and enrich our knowledge of human genetic diversity.
Relevant articles:
– TIL of The Bajau, a group of people in South East Asia who evolved to have spleens 50 percent larger than normal. This allows them to spend eight hours a day underwater, catching octopus by hand.
– Fish People: Meet Bajau tribals who can hold breath for 10 minutes underwater — But how?, The News International, Mon, 27 Nov 2023 08:00:00 GMT
– Free Divers From Southeast Asia Evolved Bigger Spleens, The Scientist, Thu, 19 Apr 2018 07:00:00 GMT
– ‘Sea nomads’ in Southeast Asia have evolved ability to dive deeper for longer, The Independent, Thu, 19 Apr 2018 07:00:00 GMT