First genetic adaptation to diving discovered in 'Sea Nomads'

  • First genetic adaptation to diving discovered in 'Sea Nomads'

First genetic adaptation to diving discovered in 'Sea Nomads'

Scientists studying the effect of this lifestyle on their biology found their spleens were larger than those of related people from the region. Crucially, a contraction of the spleen is one of the features of the so called "diving reflex" - a set of responses in mammals that occur when the head is submerged.

The researchers have published their results in the academic journal Cell.

The spleen is a fist-size organ that sits alongside the stomach.

The global research team, led by academics from the Universities of Copenhagen, Cambridge and Berkeley, therefore eliminated the possibility that larger spleens were simply a plastic response to diving and began to investigate the Bajau's genetic data.

Their lifestyle goes back at least as far as 1521: That's when a voyage led by Portuguese explorer Ferdinand Magellan - best known as the first to circumnavigate the globe - recorded coming across the seafaring Bajau. This tribe is well known for their incredible breath-holding capacities that allow them to work under water. Divers spend more than 60% of their 8-hour work days underwater, spearing fish, hunting sea cucumbers, and gathering black coral to fashion into jewelry. The spleen, when it contracts during hypoxia periods lets out a spurt of oxygenated red blood cells into the blood stream. The heart rate slows down, blood vessels in the extremities shrink to preserve blood for vital organs, and the spleen contracts. "It's like a biological scuba tank".

Ms Ilardo spent several months in Jaya Bakti, Indonesia, taking genetic samples and conducting ultrasound scans of people from the Bajau and Saluan tribes. Perhaps for this reason, large spleens have also been documented in diving seals.

This allows them to use oxygen more efficiently so they can stay underwater for longer. This helped to show that the enlargement wasn't simply a outcome of regular diving.

The brand new examine discovered that the spleens of the Bajau individuals are 50 per cent bigger than these of their land-dwelling neighbours, the Saluan.

The team was also able to find an apparent genetic basis for the size difference. "The fact that both Bajau divers and non-divers have the large spleen points to the fact that this is something they have from birth rather than something they acquired through experience over time".

Ilardo also believes her research has implications for how we think about natural selection in modern humans.

DNA analysis showed that the Bajau have a gene called PDE10A that is lacking in the Saluan. "There's not a lot of information out there about human spleens in terms of physiology and genetics", she said, "but we know that deep diving seals, like the Weddell seal, have disproportionately large spleens".

That gene variant was probably introduced into modern humans through ancient interbreeding (a process known as "introgression"), and then rose to high frequencies on the Tibetan plateau because of the advantage it conferred.

Unless you have this rare gene mutation - a "surprise finding" identified by scientists in a new study - chances are you can only hold your breath for seconds, or a few minutes at most. And it didn't seem to matter whether a Bajau person was a diver or not, which suggested that this was not merely a result of underwater training over time. But not as much research has been done on diving populations.

Researchers said the mutation the Bajau have developed is a prime example of how extensively humans can adapt to unusual environments. "It's not like (body-mass index), height or levels of high cholesterol".

These nomadic people live in waters winding through the Philippines, Malaysia, and Indonesia, where they dive to hunt for fish or search for natural elements that can be used in crafts.

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