A. The Measles Epidemic of 1728-1729
Somewhere in southern New Spain (Mexico)-probably at one of the coastal ports such as Veracruz-epidemic measles appeared in 1728. During the ensuing epidemic "Mexico, as the most populous city in the kingdom, was that which felt the punishment of the measles the most" in 1728 (Alegre 1841: III:233). The scourge had reached northern Piman territory by the end of that year, and the Tchoowaka area by early 1729.
The mission at San Ignacio de Caburica was a key post in the spread of the disease northward and for documenting its effects. A perfect situation for rapid dissemination of 17infection existed when the epidemic struck San Ignacio. Numbers of northern Pimans from a variety of settlements farther north had come to San Ignacio to work. By January 13, Father Campos had to baptize twenty-two of these laborers in danger of death from their cases of measles (Libro de Bautismos del Partido de San Ygnacio de Caburica pp. 71-72). If twenty-two workers had to be baptized in periculo mortis, the number of cases of measles was certainly much larger. It is easy to picture these sick Indians returning to their home rancherías before they were aware of their infection, thus spreading the epidemic farther northward. Almost without doubt the Tchoowaka population was infected with measles from San Ignacio in January of 1729. The epidemic mortality at San Ignacio and environs ran over sixty per cent of all deaths recorded during the year 1729 (Libro de Entierros dese Pueblo de San Ygnacio... de 1697), and the number of cases recorded by Father Campos certainly was less than the actual mortality. The mortality rate at San Ignacio can be taken as a fair estimate of the mortality in other northern Piman settlements including Tchoowaka.
By February this epidemic was sweeping through the mission Indian populations of Lower California (Alegre 1841:III:236).
This historic evidence shows that the northern Pimans were living at this time in a very large "epidemic region" which extended from at least central Mexico to the farthest frontiers of Spanish sovereignty. Under such disease conditions, 18the behavior of the Tchoowaka Pimans in burning their houses and moving to a new ranchería site when anyone died in their settlement becomes easily understood, and appears to have been a fairly realistic sort of behavior given their knowledge-or lack of it-of the germ concept and the therapies of modern medical practice. Thus it becomes significant to enquire how long the northern Pimans had lived in such an "epidemic region" and how frequently that region was swept by infectious epidemics.