The population of Mexico began to drop almost immediately after the arrival of the Spanish in 1519. A smallpox plague devastated the population of Tenochtitlan while it was under siege by the Spanish. Many other European diseases spread across Mexico and Central America in the years that followed. Even prior to the Cortez Expedition, a smallpox plague devastated the Yucatan Peninsula, the Caribbean Islands and the advanced peoples living around the Mobile and Pensacola Bays on the Southeastern Gulf Coasts.
Several European plagues that swept through Mexico during the 1500s and early 1600s killed anywhere from 30% to 80% of the indigenous population. However, the worst plagues of all might have been a homegrown beast, but it is strange that it seldom affected immigrants to Mexico who were from Europe or Africa. This fact would suggest that the plague was a mutation of some pathogen that Old World residents were long immune to.
It was a hemorrhagic fever, called cocoliztli in Nahua that could kill victims in hours, but typically killed in 3-4 days. It only affected populations living in the highlands. The host of this pathogen was apparently an animal or insect that only lived in cooler, temperate climates. Both of the mega-epidemics of this disease occurred during the worst droughts in 600 years.
The 1545 epidemic killed 85% of the indigenous population of the Mexican highlands. There were few outbreaks of the disease in the Lowlands. It was the most lethal pathogen in the history of mankind. A second outbreak of cocoliztli between 1574 and 1576 killed half of the remaining indigenous peoples of Mexico. Given the other legion of plagues that swept through Mexico between 1500 and 1800, the nation’s indigenous gene pool today probably represents something like 1% or less of what existed in 1492 . . . when Columbus sailed the ocean blue.
Did the cocoliztli pathogen strike the Southern Highlands in the 1500s? Circumstantial evidence suggests “yes.” The Tristan de Luna Expedition discovered in 1559 that much of the Mobile-Alabama-Lower Coosa River Basin had been partially depopulated by a series of plagues that followed de Soto’s path through the region. However, the chronicles of the French expeditions between 1562 & 1565 and the Pardo Expedition between 1567 & 1568 make no mention of plagues having affected the population of the Southern Highlands. The Native societies seemed to be thriving. The provinces of northern Georgia negotiated a joint marketing agreement with the French to exploit resources of the newly name Appalachian Mountains.
Scientists in several states of the Southeast and Southwest have studied historic patterns of tree rings. They determined that the worst drought in at least 1000 years occurred between 1540 and 1590. It affected all of Mexico and southern North America. Southeastern farmers, particularly the Muskogeans primarily cultivated major river bottomlands, unlike Native farmers in the other two regions. Even if a river was running very low, it was still possible to implement some form of irrigation system. However, crop productivity would have dropped dramatically.
Archaeological evidence suggests that something especially catastrophic occurred during the period between 1578 and 1585 in the Southern Highlands and the Upper Piedmont of Georgia. All of the major towns in this region were abandoned during this period, the largest ones, permanently. The surviving population of the great capital of Kusa moved 133 miles downstream on the Coosa River and reestablished a new capital. The old regional center of Etowah Mounds was permanently abandoned. All of the satellite villages of Kusa and Etowah Mounds were also apparently abandoned. The Georgia Mountains are cooler and wetter than surrounding regions. The area around Etowah Mounds until the late 20th century was swampy with many streams. The Etowah Valley was probably uninhabited until the Apalachicola moved there in 1645 from the Chattahoochee River. This general abandonment does not make sense if the cause of societal stress was solely a drought that ended in 1690.
The same patterns can be seen in the North Carolina, South Carolina and Tennessee Mountains. Major river valleys were abandoned. Mound building ceased. There is little evidence of the valleys being inhabited until the late 1600s.
Apparently, the river valleys of the Southern Highlands were viewed as being cursed for several generations; or else a pathogen lurked in these areas which made habitation dangerous. The remainder of Georgia was not uninhabited during the 1600s. Mound building stopped, but the more egalitarian lifestyle that would be labeled the Creek Indians, was evolving. “Something” that was particularly lethal definitely affected the Southern Highlands that was not as severe or non-existent in the Lower Piedmont and Coastal Plain. What it was, is still unknown.