The evolution of diet is intimately linked to human evolution: from the use of tools to break nuts, collect insects or hunt game, to the use of fire allowing more calories to be extracted from the food, and most of all the invention of agriculture with the Neolithic Era (starting around 10,000BC) certainly one of most important shifts in human behaviour.
But a study of ancient faeces (yes, 50,000-year-old poo) published today in the journal PLOS ONE, suggests that Neanderthals had more of a taste for fruit and vegetables than first thought.
For the past decades, the diet of our ancestors has been a point of debate.
Some paleoanthropologists believed that Homo neanderthalensis, who lived in a much cooler environment than the anatomically modern humans, had a diet almost exclusively carnivorous. This was based on bone accumulations and the isotopic signature (ratio of stable and unstable radioactive elements) of the fossil record.
Studies have even suggested that the dietary differences between the two populations were one possible explanation for the extinction of Neanderthals.
Meat and especially bone marrow are calorie-dense resources with essential amino acids and nutrients [ideal for brain growth](http://onlinelibrary.wiley.com/doi/10.1002/(SICI%291520-6505(1999%298:1%3C11::AID-EVAN6%3E3.0.CO;2-M/abstract), but also extremely important in cold environments. It is only logical that Neanderthals’ diet was assumed to be mainly carnivorous in order to sustain his energetic needs.
Today’s PLOS ONE paper presents a new study of coprolites (fossilised faeces) from the archaeological excavation site El Salt in Alicante, Spain.
The researchers attributed the fossil faeces to H. neanderthalensis using a blue fluorescence light (most likely a UV-A lamp, but not explicitly specified).
They looked at different organic molecules, in particular sterols, steroid alcohol naturally occurring in plants and animals.
(If you want to get technical, phytosterol – in particular 5b-stigmastanol and 5b-epistigmastanol – is a good proxy for plant consumption by animals, including humans.)
Breaking it down
While the researchers’ description of the different layers in the coprolite makes it clear that no contamination could have taken place to explain the presence of phytosterol in the layer, attribution to human origin remains putative.
Other large mammals could have left similar faeces, especially considering that the coprolites were slightly burnt.
Nevertheless, if we consider that the fossil faeces are indeed of human origin, the study clearly shows the presence of plant matter within the samples.
This could obviously indicate a mixed diet, which is certainly not that surprising. The authors briefly suggest that the intake of plant matter could have also occurred by ingesting the stomach contents of the animal they were eating.
This possibility does not change the input of plants into Neanderthal’s diet: only the means of acquisition.
Another possibility not considered by the authors is the potential use of plants for medicinal or therapeutic purposes. Indeed, the presence of inclusions (or holes) in the coprolites, attributed to parasitic nematode eggs or spores, raises the question.
A study last year showed the likely use by H. neanderthalensis of medicinal plants. In particular chamomile, known for its anti-inflammatory properties, is a common aid for stomach pain. The presence of worms can certainly trigger strong discomfort and/or pain that H. neanderthalensis may have tried to lesser by ingesting what could have been considered as a remedy.
Anyhow, despite being a preliminary study, the results are not challenging the evidence for a meat-based diet; instead they add new evidence about H. neanderthalensis complexity, by showing clearly the presence of plants in coprolites.
While not being the first evidence of plant use by Neanderthals, this new study adds another brick to our understanding of past population life and diet.