Tooth and Jaw Fossils Point to Man’s Earliest Ancestor

Photo by Wolfgang Gerber, University of Tübingen.

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Photo by Wolfgang Gerber, University of Tübingen.

The lineages of chimpanzees and human beings may have split several hundred thousand years earlier than previously thought and in the Eastern Mediterranean region and not in Africa, according to an international research team. Using computer tomography, the researchers investigated the fossil of a lower jaw from Greece and an upper molar from Bulgaria and concluded that they belonged to pre-humans.

Today’s chimpanzees are mankind’s nearest living relatives. Where the last chimp-human common ancestor lived is currently being debated, though researchers have agreed that the lineages diverged 5 million to 7 million years ago and that the first pre-humans developed in Africa. However, the new research applied computer tomography to the 2 known specimens of Graecopithecus freybergi and found that the roots of their premolars were widely fused.

“While great apes typically have 2 or 3 separate and diverging roots, the roots of Graecopithecus converge and are partially fused, a feature that is characteristic of modern humans, early humans, and several pre-humans (Ardipithecus and Australopithecus),” said Madelaine Böhme, PhD, of the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen and head of the research team.  

Nicknamed “El Graeco” by the scientists, the lower jaw has additional root features suggesting that Graecopithecus freybergi might belong to the pre-human lineage.

“We were surprised by our results, as pre-humans were previously known only from sub-Saharan Africa,” said Jochen Fuss, a PhD student at the University of Tübingen who conducted this part of the study.

Also, Graecopithecus seems to be several hundred thousand years older than the oldest potential pre-human from Africa, the 6-million to 7-million-year-old Sahelanthropus from Chad. The researchers dated the sedimentary sequence of the Graecopithecus fossil sites in Greece and Bulgaria with physical methods and got a nearly synchronous age for both fossils: 7.24 million and 7.175 million years before the present.

“It is at the beginning of the Messinian, an age that ends with the complete desiccation of the Mediterranean Sea,” said Böhme.

Geological analyses of the sediments in which the fossils were found indicate that the Sahara Desert may have originated more than 7 million years ago, while a savannah biome including giraffes, gazelles, antelopes, and rhinoceroses formed in Europe at the same time. The researchers believe that the formation of the Sahara and the spread of savannahs may have played a central role in the splitting of the human and chimpanzee lineages. 

The studies, “Potential hominin affinities of Graecopithecus from the Late Miocene of Europe” and “Messinian Age and Savannah Environment of the Possible Hominin Graecopithecus from Europe,” were published in PLOS One.

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