The Bajau people of Southeast Asia are a hunter-gatherer society who are also known as the “sea nomads” for their diving and fishing abilities. These people are known to be able to hold their breath underwater for as long as 13 minutes and have been recorded to spend up to 5 hours underwater per day when going on fishing trips.
A recent study wanted to figure what made the Bajau people able to withstand acute hypoxia conditions, as opposed to chronic hypoxia that occurs that high altitudes, and whether this ability arose from a genetic adaptation. Using the knowledge that a physiological response to diving underwater is the contraction of the spleen, the spleen size of the Bajau and a control were measured through ultra-sound and it was found that the spleen size of the Bajau people were significantly larger than the controls. Genetic mapping revealed that the Bajau had a genetic variation in PDE10A. The Bajau have increased thyroid hormone levels, specifically T4, because of the PDE10A mutation and it is strongly suggested that this hormone increases spleen size.
The spleen, in this case, is responsible for the storage of red blood cells. Because of increased spleen size, the Bajau people can store more oxygenated blood in their spleen which is then released upon natural dive responses.
DOI: 10.1016/j.cell.2018.03.054
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