Ancient human DNA suggests Columbus may not have brought syphilis to Europe after all

• 2,000-year-old bones add evidence against the idea Columbus brought syphilis to Europe.
• A European outbreak of the STI in the late 1400s was long blamed on the conquistadors.

The idea that Christopher Colombus brought back syphilis from the New World might be completely wrong.

A long-standing hypothesis held that Spanish conquistadors had picked up the sexually-transmitted infection (STI) and introduced it to Europe in the late 1400s.

But a paper published Wednesday in the peer-reviewed journal Nature adds to a mounting body of evidence that the conquistadors didn't spread the disease following their invasion of now South America.

Instead, the bacteria may have emerged a lot sooner than previously thought, Verena Schünemann, professor of Paleogenetics from the University of Basel, told Business Insider.

"Of course, we cannot prove it wrong — it doesn't work yet. But it seems that there's a much more complex story developing than these hypotheses are capturing currently," she told BI.

The timing of the arrival of syphilis in Europe is suspicious

Looking at historical literature, you would think syphilis definitely arrived with the conquistadors.

There was a big outbreak of syphilis in Europe in the late 1400s, mostly in harbor towns, seemingly out of the blue.

This lined up suspiciously with the return of sailors who accompanied Columbus on his voyage to South America.

Records of syphilis outbreaks before then were poor. Later excavations revealed bones in South America that carried lesions typically associated with a syphilis infection.

Altogether, this prompted historians to look at the voyage as an early example of how infections can spread across the globe.

Except, it's likely not that simple.

Later observations revealed some skeletons found in European sites may also carry lesions typical of a syphilis infection, long before the first contact with pre-Columbian indigenous Americans.

As the plot thickens, scientists have started looking to more modern methods of investigation to uncover what really happened.

DNA analysis reveals a more complicated story

To understand the history of syphilis better, Schünemann and her colleagues looked at 2,000-year-old bones carrying the characteristic lesions, which were found about 20 years ago in now Brazil.

They drilled tiny holes in the lesions using dentists' tools and extracted the ancient DNA left behind by the bacteria in the bone.

The analysis found that some of these lesions weren't caused by the bacteria behind sexually-transmitted syphilis but by a closely related cousin.

While this microbe is very similar to the one behind syphilis — it is part of the same family, called Treponema — it causes a completely different disease, called Bejel, which is not sexually transmitted.

It is still around today, mostly in Asia and Japan.

"We actually didn't expect to find it there," said Schünemann.

"Usually it's in arid regions, not so much in those humid coastal, tropical region. That's why we were quite surprised — this is a completely different environment than where you expect to find it," she said.

This suggests that the bones lesions alone don't guarantee that syphilis was present in South America before Columbus, poking holes in the evidence used to support the hypothesis.

The study is "really exciting because it is the first truly ancient treponemal DNA that has been recovered from archaeological human remains that are more than a few hundred years old," says Brenda Baker at Arizona State University, per New Scientist.

The mystery remains

The findings don't decisively close the door on the Columbus theory. But they do offer precious clues to better understand what happened.

"It helps us indirectly," said Schünemann.

With this ancient genome, Schünemann and colleagues were able to discover that the whole Treponema family is much older than had ever been expected.

The analysis suggests that these closely-related bacteria have a common ancestor about 14,000 years ago, said Schünemann.

That means these bacteria could easily have traveled around the world several times with the different human migrations, much earlier than Columbus's expeditions.

"We can now play around and say, okay, which hypothesis can we maybe develop from that?" said Schünemann

For Schünemann, it's more likely that the bacteria causing syphilis, Bejel, and other cousins of the Treponema family were already around in Europe, India, and the Americas, long before the first contact between Columbus and indigenous Americans.

"I think there's definitely a potential that they were around before the contact," she said.

It will be interesting, she said, to try to do the same analyses on the European bones carrying lesions and to find even older samples that could draw a better picture of the Treponema family tree.

The importance of the work goes beyond solving this historical mystery. Syphilis and its cousins are still rampant in the world today.

While they are kept under control by antibiotics, they are learning quickly how to side-step the treatments.

Left untreated, syphilis can cause permanent damage to the heart, brain, and other internal organs. Bejel, or yaws, is a childhood disease that can be disfiguring and debilitating.

By looking back at how it has evolved with humans in the past, for instance how the microbes pass genetic information back and forth, we can better predict how it will progress going forward.

"When it comes now to this increase in antibiotic resistance and so on, then it can help in the future to develop new strategies to fight this bacteria," she said.