When Christopher Columbus reached the Americas, he not only initiated a reign of extreme cruelty but he brought with him diseases that wiped out much of the population. Not long after, new infectious diseases, including syphilis, became widespread in Europe, leading to the belief these were brought back by returning sailors. However, new evidence suggests the bacterium that causes syphilis arrived in Europe too early to have been a product of those voyages, forcing a rethink of the diseases' origins.

From at least 1495, millions of Europeans started dying from syphilis and others suffered dementia, either as a result of the direct effects of the disease or from the mercury that was the most common treatment until the discovery of penicillin. Given its centuries-long grip on Europe's ruling classes, there is speculation its effects on their brains may have inflicted more misery on many subjects through bad decision-making. The fear of catching syphilis arguably also played a big part in shaping attitudes to sex still with us today.

Although less devastating for Europe than smallpox was for the Native Americans, there was nevertheless an apparent symmetry in the idea syphilis arrived from the west and a message that Europe's conquests carried a price. Now, however, Professor Verena Schünemann of the University of Zurich has thrown that into question.

Schünemann studied 15th-century corpses from Finland, Estonia, and the Netherlands whose bones carry lesions that could be indicative of syphilis and found evidence of the bacterium Treponema pallidum. One strain of T. pallidum causes syphilis, while another is responsible for yaws, a disease of the skin and bones spread mostly by children's play.

"Our data indicates that yaws was spread through all of Europe. It was not limited to the tropics, as it is today," Schünemann said in a statement. 

“The predecessor of all modern Treponema pallidum subspecies likely evolved at least 2,500 years ago. For venereal syphilis in particular, the latest common ancestor existed between the 12th and 16th century.”

Nevertheless, it may not be sheer coincidence that syphilis erupted so shortly after Columbus' return. Bacteria are notorious for sharing DNA, and Schünemann thinks it is possible there was a genetic exchange between the Old and New World syphilis strains. Although at this stage speculative, if the idea is correct, such genome swapping might have created a disease more harmful or easily transmitted than its predecessors.

An additional aspect of the work was the discovery of another Treponema subspecies that appears to have evolved in parallel to syphilis and yaws. What effect this one had on the body of infected humans and how it was spread remain unknown, and it's unlikely anyone will be volunteering to find out. Nevertheless, the genetics of this branch of the Treponema family may help reveal syphilis' true origins and the path by which it arrived in Europe.

All this isn't just ancient history. Syphilis kills around 100,000 people a year, and cases were rising pre-Covid, even skyrocketing in some places. It is suspected improved treatments for HIV are making people less careful about safer sex, while antibiotic resistance makes syphilis harder to treat.