The Moken are a tribe of people that live along the west coast of Thailand, deep in the island archipelagos on the Andaman Sea. They are known as sea-nomads, and their children have a very special adaptation not seen anywhere else in the world.
They can see meters under water as clearly as any seal or dolphin can!
Unfortunately, much of their homeland was destroyed by the Tsunami of 2004. As the Moken were moved inland, they have lost some of their cultural practices and spend less time in the sea. This generation may be the last of the sea-nomads.
The Moken children have a special talent - they can change the shape of their eyes under water.Alamy
"When the tide came in, these kids started swimming. But not like I had seen before. They were more underwater than above water, they had their eyes wide open – they were like little dolphins." said Anna Gislen, a researcher from the University of Lund in Sweden.
In 1999, Gislen and her six-year-old daughter lived with the Moken people, to observe their unique characteristics. As the tide came in, she watched the children splashing into the water and diving deep below the surface.
"They had their eyes wide open, fishing for clams, shells and sea cucumbers, with no problem at all," she tells BBC.
The children's unique ability to see clearly below water means that they spend most of their day diving in the sea for food.Alamy
Gislen created an experiment to figure out how the kids were able to see so clearly. At first, she thought that it was a kind of genetic adaptation, but the adults of the tribe didn't have this same ability.
The kids had similar vision to European children above land, but underwater, they were able to see twice as well as their European friends. Gislen guessed that they had to be doing something differently with their eyes under water.
She asked the Moken children to dive under the water and look at a card. Some had horizontal lines, and others had horizontal lines.
Each child looked at the card and then surfaced. They reported which directions the lines were moving in, and then dove back under to look at another card. With each dive, the lines would get thinner and thinner.
Moken children can change their pupil size and the lens shape of their eyes under water.Alamy
The experiment proved that these children could change the shape of the lens of their eyes and make their pupils smaller.
"Normally when you go underwater, everything is so blurry that the eye doesn't even try to accommodate, it's not a normal reflex," says Gislen. "But the Moken children are able to do both – they can make their pupils smaller and change their lens shape. Seals and dolphins have a similar adaptation."
The researcher wondered if this was special to the Moken children, or if others could learn the same adaptation.
She ran a similar experiment with some European children and, after 11 sessions, the children were able to see underwater just as clearly as the Moken children!
The reason why adults can't do the same thing, is because our lens isn't as flexible as a child's. As they age, these children won't be able to see under water like they used to.
Sadly, if the Moken don't maintain their tradition of sea diving, they could be the last generation of "dolphin-children" that the world will ever know.
"They just don't spend as much time in the sea anymore," she says, "so I doubt that any of the children that grow up these days in the tribe have this extraordinary vision."
Fore more information about the experiment, visit the BBC here.
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