The skeletons of three children who lived in what is now Vietnam thousands of years ago are challenging a long-held assumption about a family of diseases related to syphilis. Their bones carry the marks of a treponemal infection passed from mother to child, but the specific signs point not to syphilis itself but to yaws, a related disease that researchers had generally believed could not be transmitted before birth. The finding could force a rethink of how such infections are read in the archaeological record.
The children’s remains and what they showed
The remains come from two archaeological sites, Man Bac in northern Vietnam and An Son in the south, and date to roughly 4,000 to 3,200 years ago. A summary of the study describes distinctive dental abnormalities and skeletal lesions in the children, features consistent with congenital treponematosis, meaning an infection acquired in the womb rather than later in life. The pattern of damage led the team to conclude the disease was most likely congenital yaws rather than congenital syphilis.
Treponemal diseases are caused by closely related bacteria and include syphilis, yaws, bejel, and pinta. They can leave overlapping traces on bone, which is part of why distinguishing among them in ancient remains is notoriously difficult. The dental signatures in particular, malformations that develop when the infection disrupts tooth formation during early growth, provided the key evidence for a congenital, mother-to-child route in these children.
Why the yaws interpretation is a surprise
For decades, researchers operated on the understanding that among treponemal diseases, only syphilis could be transmitted from mother to child. That assumption shaped how skeletal evidence was interpreted: signs of congenital treponemal infection were routinely read as evidence of syphilis. The Vietnamese remains complicate that logic. A report on the research notes that the findings challenge the long-held view of congenital transmission, suggesting yaws may also have been able to pass to offspring before birth.
If yaws could indeed be transmitted congenitally, then some past cases identified as ancient syphilis on skeletal grounds may have been misclassified. That matters for one of the most debated questions in the history of disease: where and when syphilis originated, and whether it existed in the Old World before contact with the Americas.
The link to the syphilis-origins debate
The origin of syphilis has long been contested. One influential idea holds that syphilis emerged in a virulent form only after Christopher Columbus’s voyages connected the Americas and Europe, implying it was largely absent from the Old World before the late fifteenth century. That argument leans heavily on the interpretation of skeletal lesions, and specifically on the belief that congenital treponemal disease equals syphilis.
By showing that congenital treponematosis in ancient Southeast Asia may reflect yaws, the study weakens a pillar of that reasoning. It does not resolve the origins debate, but it widens the range of explanations for treponemal signs found in pre-contact skeletons across the Old World. Coverage from Archaeology Magazine framed the work as prompting a reassessment of how researchers infer disease identity and transmission from bone alone.
Who conducted the work
The research was carried out by an international team drawing on collaborators in Australia and Vietnam, led by bioarchaeologist Melandri Vlok, and published in a peer-reviewed osteoarchaeology journal. The team examined the skeletal material from the northern and southern Vietnamese sites with an eye toward the specific developmental markers that distinguish congenital infection, then compared those markers against the expected signatures of the different treponemal diseases.
Working with remains several thousand years old imposes real limits. Bone can preserve the scars of chronic infection, but it rarely yields a definitive microbial diagnosis without ancient DNA, which does not always survive in tropical conditions. The team’s conclusion therefore rests on the morphology of the lesions and teeth, a careful reading of physical evidence rather than a direct identification of the pathogen.
What it means for reading ancient disease
The broader takeaway is methodological. If a disease long assumed to be untransmittable before birth could in fact be passed congenitally, then the interpretive rules used to diagnose ancient skeletons need revisiting. Cases across different regions and eras may deserve a second look, with less certainty that congenital treponemal signs automatically indicate syphilis. That kind of recalibration is how the study of ancient disease advances: a single well-documented set of remains can unsettle an assumption that had quietly underpinned many earlier conclusions, opening the door to a more nuanced picture of how these infections moved through past populations.
The limits and promise of bone evidence
The study also illustrates both the power and the boundaries of paleopathology, the study of disease in ancient remains. Bone records only the chronic, long-running effects of infection, so acute illnesses that killed quickly or left no skeletal trace remain invisible, and the same lesion can sometimes result from more than one condition. That ambiguity is why researchers lean on multiple lines of evidence, dental defects, the distribution of lesions across the skeleton, and the age at which damage appears, to narrow down a diagnosis.
Ancient DNA could eventually sharpen these conclusions by identifying the specific bacterium involved, but genetic material degrades quickly in warm, humid climates like Southeast Asia’s, and it often cannot be recovered from remains thousands of years old. Until such molecular confirmation becomes possible for these particular children, the careful reading of their bones and teeth stands as the strongest available evidence, and it is enough to prompt a serious reconsideration of how one of humanity’s oldest disease families spread through early communities.
This article was produced with the assistance of AI and reviewed by Morning Overview editors prior to publication.
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