Footage shows tribe that can swim underwater for 5 hours a day after developing 'mutant gene'

If I asked you which organ was bigger in a tribe of people who for years have spent hours each day diving underwater to the point that their lung capacity is incredible, you'd probably guess it was the lungs.

However, the Bajau people who live across Indonesia, Malaysia and the Philippines are actually better endowed in the spleen department.

For almost 1,000 recorded years they've been diving into the sea, having lived off the nature that exists underwater by spearfishing and collecting shellfish.

A study of the Bajau found that they have a 'mutated gene' in the form of PDE10A, which correlates with a larger spleen size that helps them stay underwater for longer.

The Bajau can spend hours each day swimming underwater, and can hold their breath for several minutes at a time while also being able to dive down to incredible depths.

The University of Copenhagen's Melissa Ilardo, one of the authors into the study of the Bajau, told the BBC's Inside Science programme: "For possibly thousands of years, [they] have been living on house boats, travelling from place to place in the waters of South-East Asia and visiting land only occasionally. So everything they need, they get from the sea.

Diving down with wooden goggles and weights around their wastes, the Bajau have lived for countless generations off the produce of the sea. (BBC Global/YouTube)

"When they're diving in the traditional way, they dive repeatedly for about eight hours a day, spending about 60 percent of their time underwater. So this could be anything from 30 seconds to several minutes, but they're diving to depths of over 70m.”

That's pretty incredible, but you might still be wondering what a mutated gene that gives you a larger spleen has to do with a human's ability to swim underwater for longer periods at a time.

When you hold your breath and submerge yourself in the water it triggers a dive response, and you can do this to yourself just by submerging your face into cold water.

Triggering this response slows down your heart rate and makes the blood vessels in your extremities smaller in order to preserve supply for your vital organs.

This is where the spleen comes in, as it contracts due to the dive response and Ilardo said it was like 'a reservoir for oxygenated red blood cells' that functions 'like a biological scuba tank'.

They're so connected to the sea that their spleens are larger, but sadly they're also first-hand witnesses to the damage done to our underwater environment. (BBC Global/YouTube)

In fact, her study of the Bajau found that they had spleens that were about 50 percent larger than their neighbours.

Sadly, a life so closely connected to the sea also means they've been among the most affected by climate change and ecological devastation of the oceans, as they're often the first to suffer from things going wrong in the sea.

Damaged coral reefs have affected their way of life and they've seen significantly fewer fish in the sea, which is a major danger to people who for centuries have cultivated the ocean's bounty.

There are also concerns that their culture is suffering in other ways due to the pollution of plastic.

Santarawi Lalisan, an elder statesman of the tribe, told Giuseppe from Project Happiness that their culture is now dying due to Western ways.

He said: "A lot of plastic has arrived here because today the Badjao go to the supermarket and here they use plastic and no longer paper. In the past, the Badjao only used paper when they were buying something."