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Education

This nomadic community can survive longer underwater than we ever can!

indiatoday.in

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How long can you hold your breath underwater? We tried and were able to hold it for 41 seconds, to be precious. And right when we were about to feel proud of this feat, we heard about the Bajau people of Southeast Asia aka Sea Nomads.

The Bajau people of Southeast Asia spend their whole lives at sea, working eight-hour diving shifts with traditional equipment and short breaks to catch fish and shellfish for their families.

Bajau takes free diving to the extreme, staying underwater for as long as 13 minutes at depths of around 200 feet.

The term “Bajau” is applied to a variety of seafaring peoples whose scattered settlements extend across the South China Sea. Known variously as Badjaw, Bajau, Sama di Laut, or Bajo, they are one of three major groups of nomadic, or formerly nomadic, maritime foraging societies native to Insular Southeast Asia.

EXTRAORDINARY DIVING SKILLS

In a study published April 19 in the journal Cell, researchers report that the extraordinary diving abilities of the Bajau may be thanks in part to their unusually large spleens.

The adaptation, the researchers say, is a rare example of natural selection in modern humans — and one that could provide medically relevant insight into how humans manage acute hypoxia (deficiency in the amount of oxygen reaching the tissues).

“Humans are pretty plastic beings. We can adapt to a number of different extreme environments just through our lifestyle changes or our behavioral changes, so it wasn’t necessarily likely that we would find an actual genetic adaptation to diving,” said first author Melissa Ilardo, a doctoral student at the University of Copenhagen working with co-senior researchers Rasmus Nielsen of the University of California, Berkeley, and Eske Willerslev of the University of Copenhagen and the University of Cambridge.

“The first sign that we were maybe onto something was when we saw that both the Bajau divers and non-divers had larger spleens than the Saluan, a nearby, non-diving population.”

SIZE OF SPLEEN PLAYS A CRUCIAL ROLE

The spleen is an abdominal organ involved in the production and removal of blood cells in most vertebrates and forming part of the immune system. It is in the upper far left part of the abdomen, to the left of the stomach

Spleen size is significant because of the organ’s role in the human dive response, which occurs when our faces are submerged in water and we hold our breath

As our heart rate slows and blood vessels in our extremities constrict, the spleen contracts, releasing oxygenated red blood cells and making more oxygen available in the bloodstream

A larger spleen means that more oxygen gets released. Perhaps for this reason, large spleens have also been documented in diving seals

SOMETHING IS DIFFERENT ABOUT THE SEA NOMADS’ DNA

The Bajau having larger spleens than their non-diving neighbours suggested that their diving culture had shaped their physiology. But the fact that non-divers and divers both had larger spleens suggested that it wasn’t just a plastic response to spending so much time underwater. There was likely something different about the Sea Nomads’ DNA.

When the researchers scanned the genomes of the Bajau, they identified 25 sites that differed significantly from two comparison populations, the Saluan and the Han Chinese

Of these, one site on a gene known as PDE10A was found to be correlated with the Bajau’s larger spleen size, even after accounting for factors like age, sex, and height

In mice, PDE10A is known for regulating a thyroid hormone that controls spleen size, lending support for the idea that the Bajau might have evolved the spleen size necessary to sustain their long and frequent dives

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