2. Epidemics in the Aboriginal Region
Little can be said about infectious epidemics which occurred in the aboriginal epidemic region during prehistoric times. The nearly complete destruction of native documents by early Spanish churchmen has removed from the ken of man whatever documentation of such epidemics may have existed. What little can be said of the operation of this aboriginal 40epidemic region applies to the few final years of its existence, when infectious diseases introduced from Europe swept off hundreds of thousands of Indians.
a. Smallpox Epidemic of 1520
The first recorded infectious epidemic brought to North America by Europeans was the smallpox epidemic of 1520. The magnitude of this scourge will never be completely known, since it spread beyond the limits of the Aztec Empire. The dying empire was in no condition to keep records of it, and the conquering Spaniards were still too unfamiliar with the country to make more than very fragmentary records.
This epidemic was introduced by a Negro in the forces of Pánfilo de Narvaez, sent from the islands to arrest Cortez, who was operating in an extremely tenuous legal situation. This Negro landed with an infectious case of smallpox and, as he traveled from town to town infected exposed Indians and these their neighbors, until a full-scale epidemic was raging throughout the region the Spaniards had under observation (Ocaranza 1934:83) and beyond. The fearful mortality was raised by the total lack of knowledge of the disease and the principle of infection on the part of the Indians. The Spaniards laid many deaths to the native habit of frequent bathing (Días del Castillo 1956:293) and certainly the conjunction of infected and uninfected individuals in these baths (Ocaranza, 1934:83) created ideal conditions for the spread of the contagion. The epidemic caused numberless deaths among the Aztecs, beginning at the end of September and lasting for 41seventy days. So great was the mortality many families were left with no one able to prepare meals, so many died of hunger (Sahagún 1955:I:61-62).
There is no way of knowing for sure whether the contagion of 1520 spread as far northward as the upper Santa Cruz River Valley Pimans, but in all probability it did. It seems safe to assume that Aztec traders continued to carry their wares outward from the Valley of Mexico in 1520 before the final investment and siege of the city of Tenochtitlan by the Spaniards and their allies, for the Spanish retreat from their first occupation of the city had been far more of a bloody route than a defeat, and the Aztecs undoubtedly felt that they had won the decisive victory. Even though the raging epidemic tended to vitiate the fruits of this victory, the commercial drives of the petty traders probably sent them scurrying out along the trails leading northward from Tenochtitlan and dozens of other urban centres in central Mexico, just as they had been doing for centuries before the coming of the white man. After all, many a native war had been fought without stopping the traders. A certain proportion of those peripatetic traders undoubtedly carried the pox with them to infect the villagers whom they visited in their rounds until they dropped dead in their tracks or recovered.
The professional traders aside, inter-settlement communication was sufficiently frequent and intimate throughout the area of civilized influence in North America to virtually guarantee transmission of the disease to the frontiers.
42While it is impossible to say flatly that the smallpox epidemic of 1520 struck the native population of the upper Santa Cruz River Valley, the existing evidence indicates that chances are very high that it did. At the same time, the very same evidence suggests that the only immediate effect of the epidemic in this region, if it reached here, was biological. That is, it caused some reduction in population, but did not seriously affect native culture. That conclusion is implicit in the continued existence of a tightly-knit peasant society with abundant and friendly social contacts across significant language and culture barriers as late as 1540. The epidemic of 1520 was only a portent and a foretaste of years to come.
b. Measles Epidemic of 1531
Eleven years after smallpox struck the New World natives, the second major infectious epidemic spread through Mexico. This time measles was the mortal infection, again introduced by a European sick with the disease upon arrival. This time mortality was not as high as in 1520, either because the earlier smallpox epidemic had carried off most of the weaker natives, or because the latter had learned something already about escaping infection. At any rate, the Indians under Spanish rule desisted from bath ing in 1531 (Ocaranza 1934:84), evidence of the modification of a strong cultural trait in direct response to contagion and Spanish example-a cultural change in addition to those engendered by the great loss of manpower entailed in the earlier epidemic.
43As for the northern Pimans, the likelihood of their having been affected by this epidemic is almost nil. The conditions favoring their infection had ended in the destruction of Tenochtitlan by Cortez's command and the west coast civilizations by Guzmán's human bloodhounds.
In view of the vibrant peasant society which emerges, if dimly, from the accounts of northern Pimans in the Vásquez de Coronado expedition documents for 1540, it seems clear that neither the smallpox epidemic of 1520 nor the measles epidemic of 1531 affected northern Piman society seriously enough to impair its operation materially or to initiate the changes completed by the early 1700's. Those changes must have been brought about by later epidemics after the large epidemic region was re-established under Spanish auspices.