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 gum pain with makeshift "toothpicks". Some researchers even called it the oldest human habit .

But our new findings, published in the , challenge this long-held idea about human evolution. We found these grooves also appear naturally in wild primates, with little support for tooth-picking as the cause.

Even more striking, 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 gumline notches called abfraction lesions.

Together, these findings can help reshape how we interpret the fossil record and raise fresh questions about the uniquely

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