It is commonly known that peoples who live at high altitudes have evolved abilities to deal better with hypoxia, and that some are even capable of holding their breath for a longer time. But people who are live a great amount of their lifetime on water also gain the ability to hold their breath for a longer time period, and dive deeper. All these people are excellent deep divers, and one such tribe who spent most of their lives on the sea is Bajau. The Bajau are a tribe living in Indonesia, also called “Sea Nomads”, and for more than 1,000 years they have lived on the water.
These tribes relied on the sea for food and slowly evolved some exceptional freediving abilities. Bajau are outstanding divers, noted for being able to dive for the longest without coming up for air of all humans. They can spend as much as 5 hours per day underwater, and can dive to depths of around 70m (230 ft), holding their breath. One of the Bajau has been recorded as holding their breath for almost 13 minutes.
At an early age, some Bajau even intentionally break their eardrums to facilitate hunting and diving at sea. As a result, elderly Bajau can face problems in hearing properly. As subsistence divers, dependent on the sea for over a thousand years, the Bajau have many genetic adaptations to suit their specialized lifestyle.
Origins of Bajau
The Bajau have been a seafaring and nomadic people for most of their history. Several Bajau still follow this lifestyle even to this day. This explains the reason for calling them Sea Nomads. They live in the waters of the Sulu Sea, which is located off the southwestern Philippines coast, as well as several seas that surround the island of Sulawesi, in Indonesia. These areas are among the most dangerous bodies of water in the world, with high cases of open piracy as well as increasing sporadic policing.
Even with all this, the Bajau claim they have never wielded weapons, simply preferring to run away from any potential danger. They come to the shores only to bury their dead, or for brief periods while building their boats, although some Bajau started living completely on the land about 200 years ago. Several of these are found in the eastern Malaysian state called Sabah, on the island of Borneo.
The seafaring Bajau obtain most of their food from fishing, living entirely on boats. While some have abandoned the lifestyle, many still continue to remain nomadic and preserve their deep diving skills.
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The Benefits of a Larger Spleen
For most people the spleen is a mysterious organ, supporting the immune system and recycling red blood cells. However it appears to have further functions, as per a study in 2018, Bajau spleens were around 50 percent larger when compared to the Saluan people, who live on the Indonesian mainland. This points to a distinct genetic difference present in the Bajau, affecting spleen size and function.
After more research, it was found that the gene named PDE10A controls a particular thyroid hormone in the Bajau, but not in the Saluan, resulting in the larger spleen in the Bajau. This adaptation helps Bajau to have more hemoglobin-rich blood, and that the spleen contracts at depth. This gives the Bajau their amazing ability to dive for longer than most humans.
Several other genetic anomalies have been found in the Bajau, including the gene FAM178B that maintains the blood pH level when it accumulates oxygen, and BDKRB2, which is associated with peripheral vasoconstriction in response to deep dives. The large spleen and these genetic specializations play a crucial role in giving the Bajau the ability to dive longer. Such unusual spleens are also seen in many aquatic mammals, where it is also known to assist with diving for long periods.
The Pressures of Deep Diving
While the spleen may assist the Bajau in diving so well, several other adaptations also come into play. The human body behaves differently in high altitudes and in extreme depths. When humans perform deep dives, the increased pressure enables the blood vessels in the lungs to provide more blood. Sometimes however the vessels also rupture, which can cause death. This makes deep diving extremely dangerous, but the genetically inherited adaptations of the Bajau, combined with continuous practice, can prevent this from happening.
The regular training and lifestyle of Bajau may have helped in stretching their diaphragm, to make the chest wall more compliant against the lungs. The spleen also benefits in contracting the blood vessels to some extent, and this results in improved diving capabilities. Researchers are still studying how these genetic traits combine to help the Bajau to become better divers, but it is clear that the strength of the spleen contractions correlates with the ability to dive deeper.
Bajau Diving Skills Can Benefit Everyone
Understanding how the Bajau become such good divers could eventually benefit everyone. Their abilities have distinct medical implications. The body’s response to diving is quite similar to a medical condition named acute hypoxia, where one experiences rapid loss of oxygen. This condition can lead to death.
By understanding Bajau and studying more on them, the world can get a better understanding of the conditions of hypoxia. Researchers believe that the findings on Bajau can result in developments that will help in treating hypoxia. The findings will also provide a better understanding of the functioning of different genes.
However, the nomad lifestyle in the sea is under serious threat. Some Bajau have moved to wholly land-based communities, and even the seafaring Bajau are losing their boat-building skills. The Bajau are considered a marginalized group, restricted from enjoying the same citizenship rights as their mainland neighbors. The escalation in industrial fishing has also made it difficult for them to continue their lifestyle, which has led many Bajau to leave the sea.
Without any support for their lifestyle, the Sea Nomads may proceed to change their way of life. In such a scenario, lessons that the world may have found about human health from understanding the Bajau will be lost.
Top Image: The Bajau. Source: Hanafi Latif / Adobe Stock.
By Bipin Dimri
Ed Y. (2018). How Asia’s Super Divers evolved for a Life At Sea, Available at: https://www.theatlantic.com/science/archive/2018/04/bajau-sea-nomads-diving-evolution-spleen/558359/
Sam H. (2018). The Bajau Tribe Has Evolved to Be Able to Dive Deeper and Longer, Available at: https://www.deeperblue.com/tribe-that-has-evolved-to-be-able-to-dive-deeper-and-longer/
Sarah G. (2018). Sea Nomads’ Are First Known Humans Genetically Adapted to Diving, Available at: https://www.nationalgeographic.com/science/article/bajau-sea-nomads-free-diving-spleen-science