Dubbed « the nomads of the sea », the Moken, a nomadic maritime people of Southeast Asia, are said to be able to adapt their vision to see underwater, like dolphins.
Fascinated by the Moken, an extraordinary people, Anna Gislen, a scientist at Lund University in Sweden, discovered that Moken children possess an astonishing ability: the ability to adapt their vision underwater. As proof, these unrivalled fishermen who live between Burma and Thailand move underwater with impressive ease, and are able to retrieve any object or fish without difficulty.
« Normally, when you go underwater, everything is so blurry, the eye doesn’t even try to accommodate, it’s a normal reflex, » the researcher points out to the BBC. In fact, water causes the cornea to lose its refractive power. However, in Moken children, this ability is not impaired.
Unusual pupil reduction
Intrigued, Anna Gislen set out to find out more. By comparing the Moken’s vision with that of European children, the scientist was able to see that, out of the water, all the children displayed the same abilities and had the same eye structure.
However, once underwater, the Moken’s vision was found to be twice as sharp as that of Westerners. Also, Moken children are able to reduce the size of their pupils and modify the shape of their crystalline lenses, the only two ways to increase visual acuity underwater.
« Our measurements clearly show that there is a difference underwater. At the moment of diving, Moken children constrict their pupils, whereas European children do not, and pupil size differs significantly, » she explains.
Dolphin-like vision
Able to reduce the size of their pupils to the maximum limit for humans and change the shape of their crystalline lenses, it is this dual modification that enables Moken children to see clearly, even underwater. » Seals and dolphins have a similar adaptation, » stresses the scientist.
However, this ability is not irreversible. As children grow older, they lose their ability to see underwater. » As we age, our lenses become less flexible, so it seems logical that adults lose this ability to accommodate underwater, » she notes.
The secret: training
To further her research, the scientist conducted a new study on European children in Thailand and Sweden. This time, volunteers were asked to dive underwater and try to distinguish lines drawn on a map. After a month, the results showed that the European children had managed to develop abilities similar to those of the Moken.
As Anna Gislen explains, « It was different for each child, but at some point their vision suddenly improved ». She continues, « I asked them if they were doing anything different, and they said ‘no, I can just see better now' ». Following her new research, the scientist concluded that this ability developed with regular training and did not disappear. Four months later, with no marine activity whatsoever, the children had retained their ability. »
Forced to settle down after the terrible tsunami of 2004, the Moken seem to be losing their ability. » The Moken no longer spend as much time in the ocean, » laments the scientist.
Main photo credit: YouTube video screenshot