Ancient dental plaque reveals dietary habits of early human species

Archaeologists at the University of York and the Universitat Autònoma de Barcelona examined dental plaque from a 1.2-million-year-old hominin (Homo species), recovered by the Atapuerca research team in 2007 from the Sima del Elefante site in northern Spain. They extracted microfossils to find the earliest direct evidence of food eaten by early humans. These microfossils included traces of raw animal tissue, uncooked starch granules indicating consumption of grasses, pollen grains from a species of pine, insect fragments and remains of what might have been a toothpick.

All detected fibres were uncharred, and there was no evidence showing inhalation of micro-charcoal—normally a clear indicator of proximity to fire. The timing of the earliest use of fire for cooking is hotly contested, with some researchers arguing that habitual use started around 1.8 million years ago, while others suggest it was as late as 300,000–400,000 years ago.

Possible evidence of firemaking has been found at some very early sites in Africa. However, the lack of fire evidence at Sima del Elefante suggests that this knowledge was not carried with the earliest humans when they migrated from Africa. The earliest definitive evidence of the use of fire elsewhere is 800,000 years ago at the Spanish site of Cueva Negra and at Gesher Benot Ya’aqov in Israel a short time later.

Taken together, this evidence suggests that the development of fire use occurred at some point between 800,000 and 1.2 million years ago, providing a new timeline for when the earliest humans started to cook food.

“This new timeline has significant implications in helping us to understand this period of human evolution—cooked food provides greater energy, and cooking may be linked to the rapid increases in brain size that occurred from 800,000 years ago onwards,” said Dr Karen Hardy, lead author and Honorary Research Associate at the University of York and a Catalan Institution for Research and Advanced Studies research professor at the Universitat Autònoma de Barcelona.

According to Hardy, “Obtaining evidence for any aspect of hominin life at this extremely early date is very challenging. Here, we have been able to demonstrate that these earliest Europeans understood and exploited their forested environment to obtain a balanced diet 1.2 million years ago, by eating a range of different foods and combining starchy plant food with meat.”

The findings correlate well with previous research that hypothesised that the timing of cooking is linked to the development of salivary amylase, which is needed to process cooked starchy food, explained Hardy. “Starchy food was an essential element in facilitating brain development, and contrary to popular belief about the ‘Paleodiet’, the role of starchy food in the Palaeolithic diet was significant,” she said.

Anita Radini, co-author and a PhD student at the University of York, said: “These results are very exciting, as they highlight the potential of dental calculus to store dietary and environmental information from deep in the human evolutionary past. It is also interesting to see that pollen remains are preserved often in better conditions than in the soil of the same age. Overall this is a very positive step in the discipline, in terms of preservation of material in the calculus matrix.”

The study, titled “Diet and environment 1.2 million years ago revealed through analysis of dental calculus from Europe’s oldest hominin at Sima del Elefante, Spain”, was published online on 15 December in The Science of Nature journal.