This led investigators to propose that all these diseases had a single common cause—the consumption of easily digestible, refined carbohydrates. The hypothesis was rejected in the early 1970s, when it could not be reconciled with Keys’s hypothesis that fat was the problem, an attendant implication of which was that carbohydrates were part of the solution. But was this alternative carbohydrate hypothesis rejected because compelling evidence refuted it, or for reasons considerably less scientific?

The original concept of diseases of civilization dates to the mid-nineteenth century, primarily to Stanislas Tanchou, a French physician who served with Napoleon before entering private practice and studying the statistical distribution of cancer. Tanchou’s analysis of death registries led him to conclude that cancer was more common in cities than in rural areas, and that the incidence of cancer was increasing throughout Europe. “Cancer, like insanity,” he said, “seems to increase with the progress of civilization.” He supported this hypothesis with communications from physicians working in North Africa, who reported that the disease had once been rare or nonexistent in their regions, but that the number of cancer cases was “increasing from year to year, and that this increase stands in connection with the advance of civilization.”

By the early twentieth century, such reports had become the norm among physicians working throughout Africa. They would typically report a few cancers in towns where the “natives mingled with Europeans” and had copied their “dietetic and other domestic practices,” but not in those areas where lifestyles and diets remained traditional. These reports, often published in the British Medical Journal, The Lancet, or local journals like the East African Medical Journal, would typically include the length of service that the author had undergone among the natives, the size of the native population served by the hospital in question, the size of the local European population, and the number of cancers diagnosed in both. F. P. Fouché, for instance, district surgeon of the Orange Free State in South Africa, reported to the BMJ in 1923 that he had spent six years at a hospital that served fourteen thousand natives. “I never saw a single case of gastric or duodenal ulcer, colitis, appendicitis, or cancer in any form in a native, although these diseases were frequently seen among the white or European population.”

In 1908, the Smithsonian Institution’s Bureau of American Ethnology published the first significant report on the health status of Native Americans. The author was the physician-turned-anthropologist Aleš Hrdlika, who served for three decades as curator of the Division of Physical Anthropology at the National Museum in Washington (now the Smithsonian’s National Museum of Natural History). In a 460-page report entitled Physiological and Medical Observations Among the Indians of Southwestern United States and Northern Mexico, Hrdlika described his observations from six expeditions he had undertaken. “Malignant diseases,” he said, “if they exist at all—that they do would be difficult to doubt—must be extremely rare.” He had not encountered “unequivocal signs of a malignant growth on an Indian bone.” Hrdlika also noted that he saw only three cases of “organic heart trouble” among more than two thousand Native Americans he examined, and “not one pronounced instance of advanced arterial sclerosis.” Varicose veins were rare, and hemorrhoids infrequent. “No case of appendicitis, peritonitis, ulcer of the stomach, or of any grave disease of the liver was observed,” he wrote.