We Finally Know What Killed the Aztecs—And It Wasn't What You Think
It has been around 500 years since the Aztec Empire fell during the Cocoliztli epidemic, leaving behind a legacy that has been reduced to human sacrifices, fancy temples, and intricate carvings. Around the mid 16th century, the Aztecs began dying in large numbers. Estimates place the death toll between 7 and 17 million. Whatever the infected had caused them to bleed, vomit, and develop red spots on their skin before they perished. Five centuries later, and scientists now think they know which horrible disease was responsible: salmonella.
In a new study published in the journal Nature Ecology and Evolution, molecular paleopathologist Kirsten Bos and her team analyzed DNA from the teeth of Aztecs who died during one of two waves of disease (first in 1545, then again in 1576).
"There have been different schools of thought on what this disease was," Bos told NPR. "Could it have been plague? Could it have been typhoid fever? Could it have been a litany of other diseases?"
The analysis showed that an ancient type of salmonella likely caused a fever that proved deadly.
Using a new computer program called MALT, the researchers were able to match the extracted DNA to other samples, something that until recently was not possible.
"It was an analytical technique that was really the game-changer for us, " Bos said. The major advancement was this algorithm...It offers a method of analyzing many, many, many small DNA fragments that we get, and actually identifying, by species name, the bacteria that are represented."
The specific bacteria the program was able to pinpoint was Salmonella enterica Paratyphi C, but it was not able to identify its source.
One common belief is that the disease was brought to Mexico by the Europeans, but other studies have suggested that the bacteria originated in the land of the Aztecs and was made worse by drought.
"The Europeans who were observing the symptoms didn't know what it was, and Europeans got it as well," said Bos. But while they may not have been responsible for delivering the deadly package, the invaders did help open it."
We know that Europeans very much changed the landscape once they entered the new world. "They introduced new livestock, [and] there was lots of social disruption among the indigenous population which would have increased their susceptibility to infectious disease."