In ancient northern Vietnam, beauty was defined not by bright white smiles but by strikingly blackened teeth--a tradition that may seem unusual to many but continues to thrive in certain Asian cultures today.
Archaeologists have long discovered skulls with darkened teeth across various regions, but the question remained: was this discoloration intentional, a result of burial conditions, or perhaps due to the chewing of betel nut?
"Tooth blackening, a conscious alteration of teeth for a glossy black appearance, is well documented in contemporary Vietnam, yet its origins have remained somewhat mysterious," the researchers state.
A recent study has provided the earliest scientific evidence confirming that tooth blackening was a deliberate practice dating back to the Iron Age. This revelation not only sheds light on ancient beauty standards but also exemplifies how chemistry can unveil hidden cultural narratives preserved in human remains.
Deciphering the Enigma of Ancient Tooth Stains
The research centered on human remains excavated from the Dong Xa site in northern Vietnam, with burials dating back approximately 1,800 to 2,200 years, including one individual from around 400 years ago.
Researchers noted that darkened teeth alone could not definitively indicate intentional cosmetic treatment, as teeth can naturally darken due to iron-rich soil or from chewing betel nut, which imparts a reddish-brown hue. So, how could they distinguish the cause?
To clarify this ambiguity, the research team employed non-destructive scientific techniques. They analyzed teeth from three individuals using scanning electron microscopy and portable X-ray fluorescence, allowing them to assess the enamel's surface composition without harming the remains.
The findings were unexpected. The ancient teeth exhibited elevated levels of iron and sulfur, essential components in iron-tannin reactions that yield a deep black pigment known as iron-tannate.
"We identified a unique signature of tooth blackening in ancient samples, indicating that iron salts, likely combined with tannin-rich substances, were the primary agents responsible for this coloring process," the authors of the study remarked.
Iron-tannates are natural compounds found in plants like gallnuts or pomegranate rind. One Iron Age tooth also revealed high iron oxide levels, suggesting frequent application of an iron-rich paste, a pattern inconsistent with soil staining or betel nut chewing.
"If you're chewing betel nut, your teeth will appear brownish-black--not the deep black we observe here," stated Yue Zhang, the study's lead author and a researcher at Australian National University.
Recreating an Ancient Beauty Ritual
To strengthen their hypothesis, researchers replicated the ancient method by staining a modern animal tooth with an iron-gall mixture akin to traditional Vietnamese recipes.
Upon analysis, this modern sample's chemical signature closely mirrored that of the ancient teeth--showing high levels of iron and sulfur in similar ratios. This experimental validation strongly supports the notion that ancient communities employed a sophisticated chemical technique for tooth blackening.
Historically, tooth blackening was prevalent among various ethnic groups and communities in Vietnam, transcending gender and social class. Accounts from the early 20th century suggest that the process could take up to 20 days, involving repeated applications of iron-tannin pastes, followed by polishing with ash or coconut tar to achieve a glossy finish. The chemical findings from Dong Xa align with these traditional methods.
"This unique double-dyeing technique, with few ethnographic counterparts, required about 20 days to complete, with the blackened teeth remaining stable throughout an individual's life, necessitating minimal touch-ups every two to three years to maintain their shine," the study authors explained.
The timing of this practice coincides with the Dong Son cultural period and the broader Iron Age, when iron tools and materials became more accessible, enabling communities to produce stable black pigments.
Cultural Perspectives on Beauty
Rather than viewing discoloration as accidental or undesirable, scientists can now utilize specific chemical markers to determine if a cosmetic tradition was at play.
"This study provides the first archaeological insights into blackened dental traits in relation to modern Vietnamese practices, extending the ethnohistorical record by approximately 2,000 years," the researchers noted.
This research also emphasizes the cultural relativity of beauty standards. In Vietnam, blackened teeth were historically associated with adulthood, identity, and attractiveness, celebrated in ancient poems and folk songs. What might be perceived as unconventional in modern Western culture was, for centuries, regarded as an ideal.
While this study opens new avenues for understanding ancient beauty practices, questions remain. The research focused on only three individuals from one site, leaving the extent of this practice across Southeast Asia during the Iron Age still uncertain. Future studies could explore more burial sites to trace the emergence and evolution of tooth blackening.
The findings are detailed in the journal Archaeological and Anthropological Sciences.
