How evolution has turned tribe of fishermen into ‘human seals’ who dive as deep as 200ft
A TRIBE of ‘superhuman’ Indonesians have evolved larger spleens that allow them to dive more than 200ft.
A genetic adaptation – similar to one found in seals – makes their spleens 50 per cent larger than normal.
The evolutionary quirk, developed over hundreds or thousands of years, enables the Bajau tribe of ‘fish people’ in Indonesia to work eight-hour diving shifts to spear fish and octopus for their families.
The spleen is vital for this, allowing divers to stay under for longer. The organ contracts to inject oxygenated red blood cells into the bloodstream.
Members of the tribe can dive up to 230ft aided by nothing more than a set of weights and a pair of goggles. Their spleens are 50 per cent larger than those of their landdwelling neighbours, the Saluan.
‘It’s fascinating to think that they’re almost like superhumans living among us with these extraordinary capabilities,’ said Dr Melissa Ilardo of the University of Copenhagen, who led a study on the divers.
‘Natural selection is a lot more powerful than we sometimes give it credit for.’
Contraction of the spleen is a key way in which mammals respond to diving and some deep-diving seals, such as Weddell seals, have enlarged spleens. But it had never previously been seen in humans. The spleen can boost oxygen levels by nine per cent and one member of the Bajau tribe told Dr Ilardo he had once been underwater without breathing equipment for 13 minutes.
The researcher spent several months in Jaya Bakti, Indonesia, taking genetic samples and conducting ultrasound scans of people from the Bajau and land-dwelling Saluan tribes. The evidence showed that Bajau spleens were permanently enlarged, and did not get bigger simply as a response to diving. Members of the tribe who did not dive had the same characteristic.
DNA analysis showed that the Bajau have a gene called PDE10A that is lacking in the Saluan. The gene is thought to alter spleen size by adjusting thyroid hormone levels.
For more than 1,000 years, the Bajau – known as ‘Sea Nomads’ – have crossed the seas of southern Asia in house boats, catching fish by free-diving with spears. The study was published in the journal Cell