The discovery of ancient bacteria rewrites the origin of syphilis

Traces of a bacterium related to syphilis have been found in the bone of a man who lived in the mountains of Colombia more than 5,000 years ago.

The discovery shows that this group of corkscrew-shaped bacteria infected humans thousands of years earlier than previously thought, before the advent of intensive agriculture, which many researchers believe catalyzed the spread of pathogens.

Today, three subspecies of bacteria Treponema pallidum causes syphilis, bejel and yaws. The deep history of these diseases is murky, and scientists have debated where diseases like syphilis originated and how they spread. Ancient bacterial DNA and markers of infection on skeletal remains give us some clues, but these are rare and can be ambiguous.

So when researchers studying the ancient DNA of 5,500-year-old human remains in the Bogotá savanna uncovered the genome Treponema pallidum it was a surprise in the human leg bone sample.

“This finding was completely unexpected because the individual studied had no skeletal signs and Treponema infection,” he says Nasreen Broomandkhoshbacht at the University of California, Santa Cruz.

It is widely believed that many common diseases began to affect humanity after the dawn of intensive agriculture, when people began to live in denser communities. But this individual lived in a very different context, where small groups of hunters and gatherers traveled frequently and were in close contact with wildlife.

“Our results can tell us a lot about long-term evolutionary history [this bacterium] by revealing a long-term connection with the human population,” he says Davide Bozzi at the University of Lausanne in Switzerland.

When Broomandkhoshbacht, Bozzi and their colleagues compared the ancient genome to the genomes of others T. pallidum bacteria, they found it to be part of an entirely different lineage than any known modern relatives. This suggests that millennia ago, ancient syphilis relatives had already diversified in the Americas and infected humans, and the team’s analysis suggests that they had many of the same genetic traits that make today’s strains harmful.

The findings point to an early presence of these pathogens in the Americas, but it’s also possible they’ve been infecting people around the world for even longer.

Rodrigo Barquera at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, notes that the ancient strain may belong to an elusive, “missing” pathogen: Treponema carateumwhich causes a skin disease called pinta. The bacterium is known only from physical descriptions, not genetics.

Kertta Majander at the University of Zurich in Switzerland, wonders what other ancient genomes can tell us. “Was there perhaps many extinct lineages in the past and perhaps different diseases caused by these pathogens?” she says.

For Bozzi, understanding how pathogens evolve to cause diseases like syphilis and yaws is a crucial step in finding the genetic quirks that allow pathogens to infect new hosts and make associated diseases more dangerous.

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