THE Moken people of South-East Asia, who live by fishing and diving, can see twice as well underwater as Europeans. This extraordinary ability might have evolved during the thousands of years the Moken have led a semi-aquatic life, or it could be a skill learned during childhood.
The difference between the refractive index of air and that of the eye enables us to focus images. Things appear blurry underwater because water has a similar refractive index to the eye, so the eye cannot bend light enough to focus it on the retina, effectively making us very long-sighted. So Anna Gislen at the University of Lund in Sweden was intrigued when told that the Moken can spot small objects underwater without goggles.
The team tested the vision of Moken children in Thailand against children of European holidaymakers. Above water the Mokens' vision was no better. But when they asked the children ...
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