Ancient Vietnamese Skeletons Challenge Assumptions About Syphilis
For decades, one clue has stood out to archaeologists trying to spot ancient syphilis in old bones: signs that a disease passed from mother to child before birth. A new study from prehistoric Vietnam suggests that clue may not mean what researchers thought it meant.
A Disease Passed to Three Children, 3,500 Years Ago
An international research team led by Dr. Melandri Vlok, a lecturer in anatomy and physiology at Charles Sturt University’s School of Dentistry and Medical Science, examined skeletal remains from archaeological sites across northern and southern Vietnam dating to roughly 4,000 to 3,200 years ago. The findings were published in the International Journal of Osteoarchaeology.
The team studied 309 individuals from 16 archaeological sites spanning 10,000 to 1,000 years before the present. Out of that entire sample, only three young children showed diagnostic features of congenital treponematosis, a category of disease that includes syphilis, yaws, and endemic syphilis, identifiable through distinctive dental abnormalities and skeletal lesions dating back at least 3,500 years.
Why the Pattern Points Away From Syphilis
Two of the three children came from Man Bac, a site in northern Vietnam where earlier research had already documented unusually high rates of treponemal disease. What stood out in the new analysis was who, at that site, was actually getting sick. Infections at Man Bac overwhelmingly affected children and adolescents, a pattern typically associated with non-venereal treponemal diseases that spread through skin contact rather than sexual activity.
“The epidemiology of the site strongly points toward a non-venereal form of treponemal disease,” Dr. Vlok said. “Yet we still see evidence of congenital transmission. That’s the surprising part.”
Taken together, the broader pattern across the Vietnamese population suggests the children were likely affected not by venereal syphilis but by a non-venereal treponemal disease such as yaws, a tropical illness that today affects more than 150,000 people worldwide and can cause permanent disability.
Overturning a Long-Standing Assumption
The distinction matters well beyond these three individual cases. “For decades, congenital infection in archaeological remains has often been taken as strong evidence of venereal syphilis,” Dr. Vlok said. “Our research shows that this assumption may not always hold true. Other treponemal diseases may also have been transmitted from mother to child.”
That assumption has played a direct role in one of medical history’s longest-running debates: where syphilis actually came from. Researchers studying ancient skeletons have often pointed to congenital cases as evidence when arguing over whether syphilis existed outside the Americas before Christopher Columbus’s voyages. The new findings complicate that approach considerably. “If congenital transmission can occur in non-venereal treponematoses, then we need to rethink how we interpret skeletal evidence in the past,” Dr. Vlok explained. “Some cases previously labelled as congenital syphilis may represent entirely different diseases.”
To date, no confirmed biological or genetic evidence of pre-Columbian venereal syphilis has been identified anywhere in the world, inside or outside the Americas. Genetic studies of ancient remains from Europe and the Americas have instead turned up multiple different treponemal diseases, underscoring just how evolutionarily complex this family of pathogens really is.
The Difficulty of Studying Ancient Disease in the Tropics
The study also highlights a broader challenge facing researchers who study ancient pathogens. In tropical regions like Southeast Asia, ancient DNA preservation is notoriously poor, making it difficult to confirm exactly which disease affected a given population through genetic evidence alone.
At the same time, ethical standards around destructive sampling of human remains continue to evolve. “In tropical environments, recovering ancient DNA is incredibly difficult, and destructive sampling raises important ethical questions,” said co-lead author Minh Tran, a PhD student at the University of the Philippines, Diliman. “Future research must move in new directions, working in genuine partnership with communities connected to these remains, considering preservation before any biomolecular work begins.”
A More Complicated History Than Once Assumed
The researchers say the discovery underscores the remarkable adaptability of Treponema pallidum, the bacterium behind treponemal diseases. Rather than focusing narrowly on where syphilis first originated, the team argues future research should examine how different treponemal diseases evolved alongside human societies and shifting environments over time.
“Treponemal diseases have a far more complex history than we once thought,” Dr. Vlok said. “Understanding that complexity is essential if we want to reconstruct how infectious diseases shaped human history, especially as treponemal disease like yaws is re-emerging due to the climate crisis.”
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