The Bajau people of South-East Asia are sea nomads who spend most of their workday under the sea hunting for fish and sea cucumbers.
Bajaus are particularly known for their exceptional diving abilities. They can hold their breath for over three minutes at a time. They can also plunge dozens of meters below the sea surface without any diving equipment except for goggles.
Findings of a new study now reveal that their amazing ability to dive deeper underwater and go longer without oxygen is a genetic adaptation.
Study researcher Melissa Ilardo, from the University of Copenhagen, and colleagues who have been studying how the lifestyle of these people affected their biology, discovered that the Bajaus have unusually large spleens.
The fist-sized organ acts as a biological "scuba tank." The spleen serves as a reservoir of oxygen-carrying cells. When it contracts, the spleen gives the body an oxygen boost which allows a person to hold breath longer. Research on seals suggests that bigger spleen is linked to longer dive times.
"We show that natural selection on genetic variants in the PDE10A gene have increased spleen size in the Bajau, providing them with a larger reservoir of oxygenated red blood cells," the researchers wrote in their study. "We also find evidence of strong selection specific to the Bajau on BDKRB2, a gene affecting the human diving reflex.
The Bajaus provide an example of how humans evolve to better adapt to their surroundings and way of life.
Ethnic Tibetans also exhibit a genetic adaptation. Researchers of a 2014 study found that a particular gene that regulates hemoglobin became pronounced in the ancient Tibetans after they moved into high-altitude environment thousands of years ago. This gene allowed these people to live at great heights without ill consequences to their health.
Only 9 percent of the Han Chinese, who share the same ancestors with the Tibetans, possess this high-altitude gene. This gene is present in 87 percent of Tibetans.
The Inuits in Greenland thrive on a high-fat Arctic diet, but they have low rates of heart disease and diabetes. A 2015 study showed that the Arctic people also evolved, their genetic adaptations allow them to consume higher amounts of fat.
Researchers found that most Inuits have variances of genes that, they believe, slows down the natural production of omega-3 and omega-6 fats in the body. The genes also appear to decrease the levels of LDL cholesterol which is linked to heart disease. In comparison, only 15 percent of Chinese and 3 percent of Europeans have these genetic markers.