Fossil 'Toothpick Grooves' may not be from Cleaning
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- Published: Monday, 20 October 2025 12:07
- Written by Peter Ingle
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The debate around the aetiology of abfraction cavities may not be new, but it can now be argued with evidence going back to Neanderthal times.
A recent paper published in the American Journal of Biological Anthropology questions some long held assumptions about ancient non carious cervical lesions.
For decades, small grooves on ancient human teeth were thought to be evidence of deliberate tool use – people cleaning their teeth with sticks or fibres, or easing oral pain with makeshift “toothpicks”. Some researchers had even claimed it as the oldest human habit.
However the authors claim to have found these grooves also appearing naturally in wild primates, with little support for tooth-picking as the cause.
Furthermore, in a sample of over 500 wild primates, across 27 species both living and fossil, they found no trace of the common modern (human) dental condition of deep, V-shaped gumline notches.
Because teeth are the most durable part of the skeleton and often survive long after the rest of the body has decayed, anthropologists rely on them to reconstruct ancient diets, lifestyles and health.
Even tiny marks can carry important meaning. One recurring feature is the thin groove across exposed tooth roots, especially between teeth. From the early 1900’s these were labelled “toothpick grooves” and interpreted as signs of tool use or dental hygiene.
They were reported across our recent evolutionary history, that is from 2 million year old fossils to Neanderthals. It would seem that until now, no one had really checked whether other primates also have them.
A different condition, abfraction, looks very different – deep wedge-shaped notches near the gumline. These are familiar in modern dentistry and often linked to tooth grinding, forceful brushing, or acidic drinks. Their absence in the fossil record has long puzzled researchers
The researcher’s analysis was from 27 primate species, both extinct and living. The sample included gorillas, orangutans, macaques, colobus monkeys, fossil apes and more. They all came from wild populations, so their tooth wear could not have been influenced by toothbrushes, soft drinks or processed foods.
The researchers looked for non-carious cervical lesions. Using microscopy, 3D imaging and tissue-loss measurements, any lesions were documented.
About 4% of individuals had lesions. Some looked almost identical to the classic “toothpick grooves” of fossil humans, complete with fine parallel scratches and tapering shapes. Others were shallow and smooth, especially on front teeth, likely caused by acidic fruits that many primates consume in large amounts.
Despite studying species with extremely tough diets and powerful chewing forces, not a single primate showed the wedge-shaped defects familiar to present day dental teams.
The researchers argue that natural chewing, abrasive foods, or even swallowed grit can produce similar patterns. In some cases, specialised behaviours like stripping vegetation with the teeth may also contribute.
This places the classic V shaped grooves found in many patients, in a group with other dental issues, such as impacted wisdom teeth and misaligned teeth, which are rare in wild primates but common in man.
Together, these insights are shaping a growing subfield known as evolutionary dentistry, using our evolutionary past to understand the dental problems of the present. By comparing human teeth with those of other primates, it is possible to tell apart the universal wear and tear resulting from chewing, from the uniquely human, which will be the result of modern diets, behaviours and dental care.
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