For decades, tiny grooves on ancient human teeth were thought to be evidence of deliberate tool use – people would clean their teeth with a stick or fiber, or ease gum pain with makeshift “toothpicks.” some researchers also It is said to be the oldest human habit.
But our new findings, published in American Journal of Biological AnthropologyChallenge this long-held idea about human evolution. We found that these grooves also appear naturally in wild primates, which have little support for picking teeth.
What’s even more surprising is that in more than 500 wild primates, across 27 species, both living and fossil, we found no trace of a common modern dental disease: deep, V-shaped lines in the gum lines called attrition lesions.
Together, these findings may help reshape the way we interpret the fossil record and raise new questions about the specific human ways we influence our teeth today.
Why do 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 small marks can hold significant meaning. A recurring feature is thin grooves in the exposed tooth roots, especially between the teeth. from the beginning of the 20th centuryThese have been labeled “toothpick grooves” and interpreted as indicative of tool use or dental hygiene.
Our recent evolutionary history describes them as, From 2 million year old fossils to Neanderthals. But until now, no one had really investigated whether other primates also had them.
A different condition, abrasions, looks very different – deep wedge-shaped marks near the gum line. These are very common in modern dentistry and are often associated with teeth grinding, vigorous brushing or acidic drinks. Their absence in the fossil record has long puzzled researchers. Do other primates really never suffer from these?
what we did
To test these assumptions, we analyzed more than 500 teeth from 27 primate species, both extinct and living. Specimens included gorillas, orangutans, macaques, colobus monkeys, fossil apes and more.
Importantly, all the samples came from wild populations, meaning wear and tear on their teeth 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 neck of the tooth that is 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 wounds. Some fossils looked almost identical to the classic “toothpick grooves” of humans, complete with fine parallel scratches and thin shapes.
Others were shallow and smooth, especially on the front teeth, possibly due to the acidic fruits that many primates eat in large quantities.
But one absence stood out. We did not find any abrasion wounds. Despite studying species with extremely tough diets and powerful chewing forces, not a single primate showed wedge-shaped defects. Commonly seen in modern dental clinics.
What does this mean?
First, grooves resembling “toothpick” marks do not necessarily prove tool use. Natural chewing, abrasive foods, or even swallowed dirt can produce similar patterns. In some cases, specialized behaviors such as separating vegetation from teeth may also contribute. So we need to be cautious about interpreting each fossilized groove as deliberate toothpicking.
Second, the complete absence of friction wounds in primates strongly suggests that these are a uniquely human problem, linked to modern habits. It is far more likely to be caused by vigorous brushing, acidic drinks, and processed diets than by natural chewing forces.
This also keeps abrasion from causing other dental problems as well, 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, which uses our evolutionary past to understand the dental problems of the present.
why does it matter today
At first glance, the grooves on fossil teeth may seem minor. But they matter for both anthropology and dentistry.
For evolutionary science, they show why we must examine our closest relatives before assuming any specific, or unique, cultural explanation. For Modern Health, they shed light on how our diet and lifestyle alter our teeth in ways that distinguish us from other primates.
By comparing human teeth with those of other primates, we can figure out what is universal (the inevitable wear and tear of chewing) and what is uniquely human – the result of modern diet, behavior and dental care.
What will happen next?
Future research will expand to larger primate samples, examine the diet-wear link in the wild, and apply advanced imaging to see how lesions form. Its aim is to refine the way we interpret the past while discovering new ways to prevent dental disease today.
What might look like a fossilized human tooth-picking groove could just as easily have been a by-product of everyday chewing. Equally, it may reflect other cultural or dietary behaviors that leave similar traces. To sort out these possibilities, we need much larger comparative datasets of lesions in wild primates, only then can we begin to detect broader patterns and refine our interpretations of the fossil record.
Meanwhile, the absence of abrasion lesions in primates suggests that some of our most common dental problems are uniquely human. It’s a reminder that even in an everyday occurrence like a toothache, our evolutionary history is written in our teeth, but shaped as much by ancient biology as by modern habits.