Why Islands Create Rare Human Conditions
Oliver Sacks is drawn to islands because isolation changes everything. When people, animals, and plants are cut off from the outside world for long periods, unusual traits can become common. An island can turn a rare condition into part of ordinary life, and that makes it a natural place to ask how biology and culture shape each other.
His interest in colorblindness began long before he reached the Pacific. He had experienced temporary changes in vision during migraines, and he had cared for a painter who lost the ability to see color after brain injury. That raised a deeper question: what is it like not to see color from birth, and how does a person build a life around that from the beginning?
Congenital achromatopsia, or total colorblindness, is extremely rare in most of the world. People with it do not have working cone cells, the retinal cells needed for color vision and sharp daytime sight. They depend on rod cells instead, which work better in dim light, so bright sun can be painful and blinding while dusk and night may feel easier and clearer.
There was already one powerful example of an isolated community adapting to a shared condition. On Martha’s Vineyard, hereditary deafness once became common enough that hearing and deaf people alike used sign language in daily life. Deafness was not treated as a barrier to belonging. That example suggested that somewhere there might also be a community where colorblindness was not just a private burden but a shared fact of life.
That possibility led toward Micronesia, and to Pingelap, a tiny atoll where total colorblindness appears far more often than almost anywhere else on earth. Sacks traveled there with eye specialists and with Knut Nordby, a scientist who was himself born with achromatopsia. Nordby was especially important because he could explain the condition from the inside, not just as a diagnosis but as a way of seeing based on light, shadow, texture, and movement instead of color.
The journey across the Pacific also revealed another story about islands: how vulnerable they are to outside power. At military sites and former nuclear testing zones, the team saw landscapes damaged by war, contamination, and imported ways of life. On several islands, traditional foods had been replaced by packaged imports, and local people were left with the health costs while military compounds remained protected and prosperous. Against that background, the trip to Pingelap became more than a medical visit. It was also a way of seeing how fragile island worlds can be.
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