FOR DECADES, paleoanthropologists have been interested about thin grooves found on the root surfaces of ancient human and Neanderthal teeth.
They believe these as evidence of one of the earliest forms of tool use: picking one’s teeth.
These so-called “toothpick grooves” have been interpreted as traces of behaviors dating back nearly two million years — our ancestors cleaning debris from between their teeth or soothing gum pain with small sticks or fibres.
A new study challenges that interpretation. Led by researchers Ian Towle and Luca Fiorenza examined over 500 teeth from 27 wild primate species — both living and fossilized — and found that similar grooves occur in non-human primates, even in the absence of known tooth-picking behavior, phys.org reports.
The sample was drawn exclusively from wild populations, helping ensure the grooves weren’t influenced by modern habits like toothbrushes, processed foods, or dental care. The goal was to test assumptions: are these grooves really the result of deliberate tool use, or could they instead arise from natural chewing, diet, or other factors, asks The Free Library.
What the researchers found is striking. Roughly 4% of the primates studied showed lesions akin to the “toothpick grooves” found in human fossils — characterized by tapering shapes and fine parallel scratches.
Crucially, the deeper phenomenon known as “abfraction” — deep, V-shaped notches near the gum line typical in modern human teeth — was entirely absent in these wild primates, despite their harder diets and powerful chewing forces.
Both anthropology and dental science are interested. The presence of grooves similar to “toothpick marks” among non-human primates suggests that such features do not reliably indicate deliberate tool-based tooth-picking. They may instead result from wear, diet (like acidic fruit consumption), grit in food, or even regular chewing behaviors.
Or, the absence of abfraction lesions in other primates underlines that those deep V-shaped notches pretty much are a human-specific problem, tied to our modern habits — forceful brushing, acidic diets, processed foods, and other unnatural stresses on the dentition.
For anthropologists, it means revisiting claims about the “oldest human habit” of dental hygiene via toothpicks. For dentists and evolutionary biologists, it opens a window on how our modern lifestyle diverges from our primate cousins when it comes to oral wear and pathology.
The study does not entirely rule out deliberate tooth-picking in our ancestors — but it urges caution in using grooves alone as proof. The takeaway: interpreting fossilized teeth demands a deeper comparison with our primate relatives, to filter what is universal (natural chewing wear) from what is uniquely human (the result of cultural and dietary change).
Ultimately, this research shines a light on how our teeth are not just remnants of ancestral diets but living records of behavior, habit, and environment.
What looks like a simple line in a fossil tooth might tell a much more complex story — one of natural wear, diet, and evolution, rather than ancient dental tools.
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Dr. Joseph D. Lim, Ed. D., is the former Associate Dean of the College of Dentistry, University of the East; former Dean, College of Dentistry, National University; Past President and Honorary Fellow of the Asian Oral Implant Academy; Honorary Fellow of the Japan College of Oral Implantologists; Honorary Life Member of the Thai Association of Dental Implantology; and Founding Chairman of the Philippine College of Oral Implantologists. For questions on dental health, e-mail jdlim2008@gmail.com or text 0917-8591515.
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Dr. Kenneth Lester Lim, BS-MMG, DDM, MSc-OI, graduated Doctor of Dental Medicine, University of the Philippines, College of Dentistry, Manila, 2011; Bachelor of Science in Marketing Management, De la Salle University, Manila, 2002; and Master of Science (MSc.) in Oral Implantology, Goethe University, Frankfurt, Germany, 2019. He is an Associate Professor; Fellow, International Congress of Oral Implantologists; and Fellow, Philippine College of Oral Implantologists. For questions on dental health, e-mail limdentalcenter@gmail.com/PN
