The Island of the Colorblind
In 1964, while studying bird evolution on the tropical Pacific island of New Guinea, I happened to set up camp among a tribe known as the Fore. I soon found my attention drawn away from birds to a human tragedy unfolding around me. Many of the tribespeople, children as well as adults, were limping on crutches, or unable to control their facial muscles, or lying semi-paralyzed in their huts. When I asked what was wrong, their healthy relatives answered with the single word “kuru,” as if no more explanation were needed. Kuru, the Fore way of death, is now internationally notorious as a neurological disease, always fatal, and confined to that one tribe living in a group of mountain valleys only a few hundred square miles in extent.
As I proceeded through the New Guinea highlands in search of birds, every ten or twenty miles I passed into the territory of a different tribe, each with its own language, its own culture—and its own disease or genetic anomaly. The second tribe that I encountered had many albinos; the third, the world’s highest incidence of leprosy; and others had high frequencies of male pseudohermaphroditism, or of a disorder making the skin resemble that of a crocodile, or of misshapen red blood cells. Scientists have learned that each such local condition stems from various combinations of local infectious agents, adaptations, and genes.
While these pathologies may at first seem to be nothing more than exotic diseases confined to faraway peoples, they have proved enormously influential in the development of medical science, for two reasons. First, for physicians, New Guinea’s mountain valleys harbor so many locally distinct human populations that the resulting range of entrenched diseases rivals that of Europe and the United States, with their much larger but more homogeneous human populations. Some of those diseases first recognized in New Guinea turned out to provide decisive insights into more widespread conditions—notably kuru, which has been the best model for understanding Creutzfeldt-Jakob disease, mad cow disease (alias bovine spongiform encephalopathy), and possibly Alzheimer’s disease. Second, for evolutionary biologists, New Guinea’s human populations allow us to study processes of evolution and genetic change under conditions much more relevant to ourselves than the usual animal population studies cited in any textbook of biology.
Two such diseases on other tropical Pacific islands are subjects of the latest book by the distinguished neurologist and author Oliver Sacks. Both diseases have a known or possible genetic basis: achromatopsia (complete color blindness) on Pingelap, and lytico-bodig (a highly variable neurological disorder) on Guam. Dr. Sacks is already deservedly admired for previous successful books (e.g., Awakenings, An Anthropologist on Mars, The Man Who Mistook His Wife for a Hat) distinguished by beautifully written, poignant studies of individuals with neurological diseases, and by Dr. Sacks’s ability to bring himself and his readers into the unusual states of mind of his patients. The current…
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