After the French king Charles VIII invaded Italy in 1494, an unknown and disfiguring disease erupted in the army camps and duly spread across Europe when the men returned to their homelands the following year.
The epidemic is regarded as the first historical account of syphilis, but where the disease came from has been debated by scholars ever since. One camp believes it emerged in the Americas, and was brought to Europe by Columbus in 1493. Another suspects it was lurking in Europe before the explorer set sail.
Now, ancient DNA recovered from skeletons across the Americas has shed light on the mystery. The disease-ravaged bones, which predate Columbus’s first voyage to the New World, harboured genomes of bacteria from the syphilis disease family, suggesting the infection had its roots in the Americas.
Syphilis is part of a small family of diseases that includes yaws and bejel. While syphilis is found around the world, yaws and bejel are neglected tropical diseases seen mostly in equatorial regions. All three conditions are caused by strains of Treponema pallidum bacteria.
“We were able to reconstruct five genomes from these bones and we see that they are sister lineages to the modern strains of the bacterium that is circulating in humans today,” said Dr Kirsten Bos, the group leader for molecular paleopathology at the Max Planck Institute for Evolutionary Anthropology in Leipzig. “They all appear to have emerged in the Americas.”
Writing in Nature, Bos and her colleagues describe how they extracted and reconstructed ancient T pallidum DNA from the skeletal remains, which included a hip bone from Argentina, a lower leg bone from Chile, upper and lower leg bones from Mexico and a tooth from Peru.
Because the researchers knew the age of the bones from radiocarbon dating, they were able to trace the different strains of the bacteria back to a common ancestor that lived at most 9,000 years ago.
“This is a time when humans were already well established in the Americas, and they were not interacting with populations in other parts of the world. They were basically geographically and biologically isolated in the Americas,” Bos said.
The finding suggests syphilis and its known relatives had their roots in the Americas, but spread globally through human trafficking and European expansions across the Americas and Africa in the decades and centuries after the early epidemic.
It is unlikely to draw a line under the debate, however.
“I don’t think we’re solving the mystery necessarily, because there are still so many important questions we have to answer,” Bos said. “We’re looking at very limited sources of data, and we’re trying to analyse them and in a very holistic, comprehensive way, and to be very open-minded. I think the narrative will continue to be debated.”
