A large comparative study of primate teeth shows that grooves once linked to ancient human tooth-picking can form naturally, while some common modern dental problems appear uniquely human.
For many years, narrow grooves found on ancient human teeth were widely interpreted as signs of intentional behavior, such as cleaning teeth with sticks or fibers, or relieving sore gums with simple “toothpicks.” Some scholars even described this as the earliest known human habit.
New research now calls that interpretation into question. Our findings, published in the American Journal of Biological Anthropology, show that similar grooves form naturally in wild primates, offering little evidence that tooth picking was responsible.
Even more surprising, when we examined more than 500 wild primates spanning 27 living and fossil species, we found no evidence of a common modern dental condition. These deep, V-shaped notches along the gumline, known as abfraction lesions, were entirely absent.
Taken together, the results suggest a need to rethink how dental marks in fossils are interpreted and highlight that some features affecting human teeth today may be uniquely tied to modern lifestyles rather than deep evolutionary history.
Why teeth matter in human evolution
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. Since the early 20th century, these have been labelled “toothpick grooves” and interpreted as signs of tool use or dental hygiene.
They have been reported across our recent evolutionary history, from 2-million-year-old fossils through to Neanderthals. But 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 very common in modern dentistry and often linked to tooth grinding, forceful brushing, or acidic drinks. Their absence in the fossil record has long puzzled researchers. Do other primates really never suffer from them?
What we did
To test these assumptions, we analyzed more than 500 teeth from 27 primate species, both extinct and living. The sample included gorillas, orangutans, macaques, colobus monkeys, fossil apes, and more.
Crucially, all specimens came from wild populations, meaning their tooth wear could not have been influenced by toothbrushes, soft drinks, or processed foods.
We looked for non-carious cervical lesions – a name for tissue loss at the tooth neck not caused by decay. Using microscopes, 3D scans, and tissue-loss measurements, we documented even the smallest lesions.
What we found
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.
But one absence stood out. We found no abfraction lesions at all. Despite studying species with extremely tough diets and powerful chewing forces, not a single primate showed the wedge-shaped defects so commonly seen in modern dental clinics.
What does this mean?
First, grooves that resemble “toothpick” marks don’t necessarily prove tool use. Natural chewing, abrasive foods, or even swallowed grit can produce similar patterns. In some cases, specialized behaviors like stripping vegetation with the teeth may also contribute. We therefore need to be cautious about interpreting every fossil groove as deliberate toothpicking.
Second, the complete absence of abfraction lesions in primates strongly suggests these are a uniquely human problem, tied to modern habits. They are far more likely caused by forceful brushing, acidic drinks, and processed diets than by natural chewing forces.
This places abfraction alongside other dental issues, such as impacted wisdom teeth and misaligned teeth, which are rare in wild primates but common in humans today. Together, these insights are shaping a growing subfield known as evolutionary dentistry, using our evolutionary past to understand the dental problems of the present.
Why it matters today
At first glance, grooves on fossil teeth may sound trivial. But they matter for both anthropology and dentistry.
For evolutionary science, they show why we must check our closest relatives before assuming a specific, or unique, cultural explanation. For modern health, they highlight how profoundly our diets and lifestyles alter our teeth in ways that set us apart from other primates.
By comparing human teeth with those of other primates, we can tease apart what’s universal (the inevitable wear and tear of chewing) and what’s uniquely human – the result of modern diets, behaviors and dental care.
What’s next?
Future research will expand to larger primate samples, investigate diet-wear links in the wild, and apply advanced imaging to see how lesions form. The aim is to refine how we interpret the past while finding new ways on how to prevent dental disease today.
What may look like a fossil human tooth-picking groove could just as easily be the by-product of everyday chewing. Equally, it might reflect other cultural or dietary behaviors that leave similar marks. To untangle these possibilities, we need much larger comparative datasets of lesions in wild primates, only then can we begin to trace broader patterns and refine our interpretations of the fossil record.
Meanwhile, the absence of abfraction lesions in primates suggests that some of our most common dental problems are uniquely human. It’s a reminder that even in something as everyday as a toothache, our evolutionary history is written in our teeth, but shaped as much by modern habits as by ancient biology.
Reference: “Non-Carious Cervical Lesions in Wild Primates: Implications for Understanding Toothpick Grooves and Abfraction Lesions” by Ian Towle, Kristin L. Krueger, Kazuha Hirata, Mugino O. Kubo, Anderson T. Hara, Joel D. Irish, Carolina Loch, Matthew R. Borths and Luca Fiorenza, 29 September 2025, American Journal of Biological Anthropology.
DOI: 10.1002/ajpa.70132
Adapted from an article originally published in The Conversation.
Funding: Ian Towle receives funding from the Australian Research Council (ARC DP240101081). Luca Fiorenza receives funding from the Australian Research Council (ARC DP240101081).
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3 Comments
In what amazes evolutionists amazes me. This is a big nothing-burger. Nenaderthals were 99.84% identical in the DNA sequences to us. So both of us using toothpicks? No big deal. No pertinence to evolution. What are the big differences. It is the epigenetic modifications that make adaptations without any DNA sequence involvement. No mutations involved. However, evolutionists call epigenetic modifications as being ‘DNA differences’.
That is is a lie. The modifications are chemical by methylations changes that turn genes up and down or on and off. Histone changes too. Epigenetic changes are not DNA mutations to make evolution seem real. It is smoke and mirrors.
I, as a for instnace, has 92% more Neanderthal gene expression than average human beings. I am in pretty good health. I look 15 years younger than I really am. Epigenetic modifications, making gene expression differences has an intelligent design implication, not a Godless evolution one. Too many people have been suckered by this sleight of hand deception.
The epigenome producing the epigenetics, gene expression modifications into adaptations is like a software program running overtop the DNA hardware. This implies creation. The simpler answer. The ‘dots of the picture’ by scientism giving a Godless existence has much money and political science benefits for those who push it. Still water runs deep. What is in the depths of all this? It is a battle of good vs evil with Jesus Christ as the Creator, also known as The Word in Genesis. There’s your science. There is the truth.
What study showed YOU had 92% more Neanderthal epigenetic gene expression than other humans? In fact, what study (authors names and date of publication) demonstrates a continuous range of epigenetic influence between Neanderthals and modern humans.
And what epigenetic conditions would trigger the changes in regulatory genetic traits that would impact the phenotype to allow Neandertals to become modern or vice-versa?
We do know the relative levels of genetic (DNA) distinction between those two groups and the levels of distinctively evolved Neanderthal genome that has been found in modern human populations through prior introgression (hybridization).
No modern humans have the degree of or entire set of phenotypic traits that classic Neandertals demonstrate.
What study showed YOU had 92% more Neanderthal epigenetic gene expression than other humans? In fact, what study (authors names and date of publication) demonstrates a continuous range of epigenetic influence between Neanderthals and modern humans.
And what epigenetic conditions would trigger the changes in regulatory genetic traits that would impact the phenotype to allow Neandertals to become modern or vice-versa?
We do know the relative levels of genetic (DNA) distinction between those two groups and the levels of distinctively evolved Neanderthal genome that has been found in modern human populations through prior introgression (hybridization).
No modern humans have the degree of or entire set of phenotypic traits that classic Neandertals demonstrate.