Hrdlika considered the possibility, which Keys would raise fifty years later, that these Native Americans were unaffected by chronic disease because their life expectancy was relatively short; he rejected it because the evidence suggested that they lived as long as or longer than the local whites.

In 1910, Hrdlika’s field observations on cancer were confirmed by Isaac Levin, a Columbia University pathologist, who surveyed physicians working for the Indian Affairs Bureau on reservations throughout the Midwestern and Western states. Levin’s report, entitled “Cancer Among the North American Indians and Its Bearing upon the Ethnological Distribution of the Disease,” discussed the observations of 107 physicians who had responded to his survey, with their names, locations, size of practice, duration of practice, and number of cancers diagnosed: Chas. M. Buchannan, for instance, practiced fifteen years among two thousand Indians with an average life expectancy of fifty-five to sixty years and saw only one case of cancer; Henry E. Goodrich, practicing for thirteen years among thirty-five hundred Indians, saw not a single case. Levin’s survey covered over 115,000 Native Americans treated by agency doctors for anywhere from a few months to two decades and produced a total of twenty-nine documented cases of malignant tumors.

The two most comprehensive attempts to deal with the question of cancer in isolated populations were in The Natural History of Cancer, with Special Reference to Its Causation and Prevention, published in 1908 by W. Roger Williams, a fellow of the British Royal College of Surgeons, and The Mortality from Cancer Throughout the World, published in 1915 by the American statistician Fredrick Hoffman. In The Natural History of Cancer, Williams marched from continent to continent, region to region. In Fiji, for instance, in 1900, among 120,000 aborigines, Melanesians, Polynesians, and “Indian coolies,” there were only two recorded deaths from malignant tumors. In Borneo, a Dr. Pagel wrote that he had been in practice for ten years and had never seen a case. Williams also documented the rising mortality from cancer that Tanchou had reported in the developed nations. In the United States, the proportional number of cancer deaths rose dramatically in the latter part of the nineteenth century: in New York, from thirty-two per thousand deaths in 1864 to sixty-seven in 1900; in Philadelphia, from thirty-one in 1861 to seventy in 1904.

Hoffman dedicated the better part of his career to making sense of these observations. He began his cancer studies as chief statistician of the Prudential Insurance Company and continued them as part of an investigation of the Committee on Statistics of the American Society for the Control of Cancer (a predecessor of the American Cancer Society, of which Hoffman was a founder). In The Mortality from Cancer Throughout the World and then again in Cancer and Diet, his 1937, seven-hundred-plus-page update of the evidence, Hoffman concluded that cancer mortality was increasing “at a more or less alarming rate throughout the entire world,” and this could only partially be explained by new diagnostic practices and the aging of the population.