Examinations of the teeth of various hominins helps to understand their distribution in Europe and their evolution in the Pleistocene

Two articles published in the journal “PLOS ONE” describe two research on Pleistocene hominin teeth conducted by two teams with various researchers in common. A team led by Laura Martín-Francés of the French University of Bordeaux discovered various characteristics of Neanderthal teeth in the molars of a previous species named Homo antecessor from the Early Pleistocene. A team led by Clément Zanolli of the French University of Toulouse III Paul Sabatier examined the oldest dental remains discovered in Italy with an age estimated at about 450,000 years ago, concluding that they were similar to those of Neanderthals and distinct from those of modern humans.

Teeth characteristics such as the proportions of the dental tissues and enamel thickness are one of the methods to recognize the various species of ancient hominins since they’re rather specific to each one. As for the Neanderthals, their enamel was thin in a specific way compared to that of other hominins, but it’s not clear how it evolved that way. Teeth evolution in the various hominins is one of the pieces in the reconstruction of the mosaic of the evolution of the various species.

The team led by Laura Martín-Francés examined 17 molars belonging to Homo antecessor, a species that lived between 1.2 million years ago and 800,000 years ago, the oldest species of the genus Homo discovered in Europe. The teeth were found in the TD6 level of the Gran Dolina cave in the Sierra of Atapuerca, located east of Burgos in northern Spain and are estimated to be between 800,000 and 900,000 years old. They were compared with over 300 molars of other species of the genus Homo, which include Homo sapiens, from around the world. A micro-CT scan allowed to obtain accurate examinations of the teeth with high resolution images in a non-invasive way.

The result is that the molars of Homo antecessor don’t have a thin enamel like Neanderthals’ but the global distribution of enamel and dentin is more similar to Neanderthals’ than to other hominins. This hominin of the lower Pleistocene have an enamel similar to that of most hominins. However, some characteristics present only in this species subsequently became typical of Neanderthals.

The image above (Martín-Francés et el., 2018 CC-BY) shows a cartographic examination of a Homo antecessor molar discovered in Gran Dolina (ATD6-1103) compared with one of Neanderthal (NEA) and one of a modern human (MH). The variation of the enamel thickness is indicated by a color scale that goes from dark blue for the minimum thickness to the red one for the maximum one.

The team led by Clément Zanolli examined teeth discovered in two Italian locations: Fontana Ranuccio, about 50 kilometers from Rome, and Visogliano, about 18 kilometers from Trieste. The image below (Zanolli et al., 2018 CC-BY) shows a microtomographic representation of teeth found in Fontana Ranuccio (FR1R and FR2) and in Visogliano (from (Vis. 1 to Vis. 6).

These teeth are estimated to be around 450,000 years old and are among the few fossil remains discovered in Europe dating back to the Middle Pleistocene. The researchers used a micro-CT scan to examine them and compare them with those of Neanderthals and modern humans and concluded that those from both sites are similar to Neanderthal teeth and different from those of modern humans.

The problem is trying to identify the various species of hominins that lived in Europe but also in Asia in the Pleistocene and to reconstruct their evolution. Establishing that the teeth discovered in Fontana Ranuccio and in Visogliano have characteristics compatible with those of Neanderthals suggests that 450,000 years ago there was already a diversification among the hominins.

Each fossil analyzed offers new information on the distribution of various species on the territory and their changes over the millennia. This is important because the fossils indicate that in the Pleistocene Europe and Asia were inhabited by different species of hominins. The possibility of conducting very sophisticated and at the same time non-invasive analyzes can greatly help these researches even starting from a few teeth. In some cases, advances in genetic techniques may offer major contributions but only in some cases DNA fragments were preserved, so having other technologies to examine the fossils remains crucial.

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