An international team led by Dr. Melandri Vlok of Charles Sturt University examined skeletal remains from 16 archaeological sites across Vietnam spanning 10,000 to 1,000 years before present. The study, published in the International Journal of Osteoarchaeology, identified three young children with distinctive dental abnormalities and skeletal lesions diagnostic of congenital treponematosis dating back at least 3,500 years.
Treponematosis encompasses several diseases caused by related bacteria, including venereal syphilis, yaws, and endemic syphilis. For decades, researchers have treated evidence of congenital infection in archaeological remains as a strong indicator of venereal syphilis specifically.
The overall infection pattern at the sites, particularly at Man Bac in northern Vietnam, points away from venereal transmission. Most cases occurred among children and adolescents, a distribution consistent with non-venereal diseases spread through skin contact rather than sexual activity.
Despite this population-level evidence for a non-venereal disease such as yaws, two of the three congenitally infected children came from Man Bac. This demonstrates that mother-to-child transmission occurred in a non-venereal treponemal disease, contradicting the previous assumption that congenital transmission was unique to syphilis.
The finding complicates the long-running debate about syphilis origins. Scientists have frequently cited congenital infection in pre-Columbian remains outside the Americas as evidence for early syphilis. The new research suggests some cases previously labeled congenital syphilis may represent other treponemal diseases entirely.
Ancient DNA preservation in tropical Southeast Asia is extremely poor, making genetic confirmation of the specific pathogen difficult. Co-lead author Minh Tran, a PhD student at the University of the Philippines Diliman, noted that destructive sampling for DNA also raises ethical concerns requiring genuine partnership with descendant communities.
The researchers argue that future work should examine how different treponemal diseases evolved alongside human populations and changing environments, rather than focusing solely on syphilis origins. Dr. Vlok emphasized that understanding this complexity is essential as diseases like yaws re-emerge amid the climate crisis.
3,500-year-old skeletons challenge what scientists thought they knew about syphilis
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