Early humans living more than a million years ago may already have had notions of dental hygiene, cleaning their teeth with some kind of toothpicks. While meat formed a large part of their diet, a close examination of the teeth suggests that plants would also have been included in our ancestors' meals.

The authors of this study, published in The Science of Nature, looked at some of the earliest ancient hominin fragments ever found in Europe. Discovered in Sima del Elefante, Spain, they are 1.2 million years old. Little is known about the diet of people who lived so far back in time, in particular regarding their use and consumption of plants.

The researchers focused on a hominin molar recovered at the site. They removed the dental tartar on it to analyse it and identify entrapped food remains. Through this process, they revealed one of the earliest direct evidence for foods consumed in the genus Homo.

They found meat remains, including traces of a butterfly's wing and a fragment of an insect leg.

More surprising, they identified plant fibres and starchy carbohydrates from two different plants. There was also evidence for conifer pollen grains which indicates that this early human group may have lived near a forest.

Fire use and hygiene

The question of when hominins first started using fire has long been debated and a clear answer has yet to emerge. Here, the intact nature of the starch granules in the molar tartar and the uncharred fibres suggest that at the time, the hominids at Sima del Elefante had not mastered the use of fire and ate their food raw. This hypothesis is further confirmed by the fact that the teeth show signs of heavy use. They must therefore have been used to grip and chew raw materials.

dental hygiene
Early humans had notions of dental hygiene. Here scientists show a cluster of starch granules in microfossils extracted from dental calculus Karen Hardy

The scientists also noticed small pieces of non-edible wood from a groove at the bottom of the molar they examined. Known as the interproximal groove, it is thought to be caused by regular tooth picking. The small wooden fragments may thus have served as small wooden toothpicks.

Previously, other examples of dental hygiene practices had been found, but in archaic humans who lived much later. Indeed, interproximal grooves had been discovered in a much younger 49,000 year old Neanderthal man.

This new study, nevertheless, provides the earliest evidence of dental hygiene among early humans – even though the amount of tartar accumulated on the molar suggests that toothbrushes were far from being invented.