"Normally, severe blur does not elicit accommodation, and no accommodative response can be found in untrained European children." The Moken's pupils also adapt, constricting to a mere 0.08 inch (1.96 millimeters). The European children's pupils constricted to only a tenth of an inch (2.5 millimeters).
"Their constricting pupils improve vision further," Gislén said. "It's the same process that improves focal depth if using a camera with a smaller aperture."
The Moken children use these adaptations to forage for small clams and sea cucumbers at depths of 10 to 13 feet (3 to 4 meters). It's a key to survival, but is it learned, or might there be a genetic component?
"I think that in general this is very hard to know," Gislén said. "Genes and environment are so intertwined it's hard to separate them. What I do know is that we have [more recently] trained European children to become as good at underwater tasks as the Moken children. So training seems to do the trick."
"However," she continued, "I cannot rule out that genes may influence the speed of learning, or that the Moken children may be better at things we did not test underwater, due to some genetic component."
Gislén hopes to continue her research further afield, testing and comparing the underwater vision of other sea nomads who dive even more than the Moken. Research is expensive, however, and further limited by the shy and reclusive nature of many sea peoples.
Other subjects may be similarly elusive.
"I have also heard about monkeys that forage in the waters around Sri Lanka," Gislén said. "It would be interesting to see whether they use the same strategies as humans apparently do to see food items on the seafloor."
As fascinating as her study has been, Gislén stresses that her research is just a single example of the incredible adaptive powers of the human body.
"I think that the human body is extremely flexible, much more than we may be aware of," she said.
"The diving response is another good example of adaptation," she continued. "Some tribes of sea nomads in the Philippines can dive down 200 to 230 feet (60 to 70 meters), pick some pearls and then go up again, holding their breath for about six to seven minutes., Gislén added, "Europeans told to do the same thing would just shake their heads and say it was impossible. But clearly it's not."
Neither is clear underwater vision, apparently, if you have the right trainingor if you happen to be a Moken.
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