OPENING your eyes underwater can be an enlightening experience, especially if you’re floating over a coral reef in a sea packed with tropical fish. But without goggles it’s usually just a big blur – unless, that is, you belong to the Moken people, who live on the Surin Islands off the west coast of Thailand. Moken children are seeing the underwater world with a clarity that most people only see in photographs.
Anna Gislen, who studies vision at the University of Lund in Sweden, began studying Moken children a few years ago after hearing they could pick out small mussels on the seabed. She compared their underwater vision with that of European children by asking them to identify the orientation of fine black-and-white lines from a distance. She found the Moken could pick out lines more than twice as fine, even though out of the water they did no better than Europeans (see 91av, 17 May 2003, p 14).
Gislen discovered that the Moken achieve their underwater super-sight by constricting their pupils, which sharpens their focus. Since then she has been training Swedish children to do the same thing. She found that they could learn the trick in four to six months, after which their pupils constricted automatically whenever they put their heads underwater. This implies that the Moken’s skill is mostly learned, though there could still be a genetic element. Genes could, for example, help them learn faster.
Advertisement
Gislen thinks people can be taught all kinds of underwater skills that appear impossible. She hopes to investigate tribes in the Philippines whose members can dive to 70 metres in a single breath.
Many of the Moken lost their homes in the tsunami last December, but anthropologists who have visited them say virtually all of them survived by following the advice of their elders and running to high ground when the sea retreated.
