The diets of one of our closest ancient human relatives, the Neanderthals (Homo neanderthalensis) continues to be the topic of scientific debate.
Some studies of Neanderthal dental calculus, from the Iberian Peninsula in southwestern Europe, appear to indicate that individuals there were major consumers of plants, whereas other research outside of Iberia has suggested that they almost ate meat entirely.
Now, researchers have used new analytical techniques on a Neanderthal molar from the Gabasa excavation site in Spain, and their findings suggest that the Neanderthals that lived there appear to have been carnivores.
Read more: Neanderthals ate brain food from the sea.
Using isotope analysis to determine diet
Figuring out Neanderthals’ diets has previously relied on analysing bone and tooth collagen using nitrogen isotope analysis.
All atoms of the same element have the same number of protons, but they don’t always have the same number of neutrons. These are called isotopes and by studying the slight differences in their concentrations scientists can find out useful information.
For instance, analysing the concentrations of nitrogen isotopes in a biological sample can determine the trophic or nutritional level of an organism. This is because heavier nitrogen isotopes (with more neutrons) tend to accumulate higher up in the food chain.
But collagen degrades over time, depending on climatic and environmental conditions, so this method can often only be used in temperate environments and only rarely on samples older than 50,000 years.
When these conditions are not met nitrogen isotope analysis becomes very complex, or even impossible, which was the case for the molar analysed in this study.
So, scientists from the French National Centre for Scientific Research decided to analyse the zinc isotope ratios present in the tooth enamel instead. Tooth enamel is the thin mineralised outer covering of the tooth, which is much less susceptible to degradation.
Zinc has five stable isotopes, but it’s the ratio of 66Zn to 64Zn (indicating the number of neutrons) that tells scientists whether an animal is an herbivore or a carnivore. The lower the proportions of the Zinc isotopes (more 64Zn compared to 66Zn), the more likely the teeth belonged to a carnivore.
By also analysing the bones of animals from the same time period and geographical area – including carnivores like lynxes and wolves, and herbivores like rabbits and horses – the researchers were able to show that this Neanderthal was most likely a carnivore.
“Our results demonstrate that the Neandertal individual from Gabasa shows a Zn isotope signature of a top-level carnivore, similar to that observed for nitrogen isotopes for other sites with Neandertal occupation,” the authors write in the study. “Of all the animal taxa analysed in Gabasa, the Neandertal specimen easily exhibits the lowest Zn isotope ratio.
“Our successful analysis of Zn isotopes from a Pleistocene hominin tooth paves the road for a refined understanding of Neanderthal diet.”
To confirm their conclusions, the scientists hope to repeat the experiment on individuals from other sites, especially from the Payre site in south-east France, where new research is under way.