3,500-year-old skeletons challenge syphilis origin theory

A study of 3,500-year-old skeletons from Vietnam suggests that congenital transmission of treponemal diseases—historically considered a hallmark of venereal syphilis—may also occur in nonvenereal forms such as yaws. The research, led by Dr. Melandri Vlok of Charles Sturt University, was published in the International Journal of Osteoarchaeology on August 12, 2026.

The team examined 309 individuals from 16 archaeological sites across Vietnam, spanning 10,000 to 1,000 years before present. Three children showed dental abnormalities and skeletal lesions consistent with congenital treponematosis. Two were from Man Bac in northern Vietnam, a site with unusually high rates of treponemal disease, mostly among children and adolescents—a pattern more consistent with skin-contact spread than sexual transmission.

The findings challenge a long-standing assumption in paleopathology. According to Dr. Vlok, congenital infection in ancient remains has often been taken as strong evidence of venereal syphilis, but this may not always hold true. If nonvenereal treponematoses can also pass from mother to child, some cases previously labeled congenital syphilis may represent entirely different diseases.

This has implications for debates over the origin of syphilis and whether it existed outside the Americas before Columbus. No confirmed pre-Columbian venereal syphilis has been identified genetically, and studies show multiple treponemal diseases in ancient populations. In tropical Southeast Asia, ancient DNA is poorly preserved, and destructive sampling raises ethical concerns, according to co-lead author Minh Tran of the University of the Philippines, Diliman.

The researchers argue that treponemal diseases have a more complex history than once thought. Dr. Vlok notes that yaws is re-emerging due to the climate crisis, making it essential to understand how these diseases evolved alongside human societies.