An international team of paleoanthropologists, led by Professor Madelaine Böhme of the University of Tübingen, Germany, has analyzed 7.2 million-year-old remains of the hominin Graecopithecus freybergi and came to the conclusion that they belong to pre-humans.

Humans and chimpanzees split from their last common ancestor several hundred thousand years earlier than believed, according to Prof. Böhme and co-authors.

Their findings, published in the journal PLoS ONE, also indicate that the split of the human lineage occurred not in Africa, but in the Eastern Mediterranean.

“Present-day chimpanzees are humans’ nearest living relatives. Where the last chimp-human common ancestor lived, however, is a central and highly debated issue in paleoanthropology,” Prof. Böhme and co-authors said.

“Scientists have assumed up to now that the lineages diverged 5-7 million years ago and that the first pre-humans developed in Eastern Africa.”

“According to the 1994 theory of French paleoanthropologist Yves Coppens, climate change in the region could have played a crucial role.

“Our discovery outlines a new scenario for the beginning of human history,” added co-author Professor David Begun, from the University of Toronto.

The researchers analyzed two known specimens of Graecopithecus freybergi: a lower jaw from Pyrgos, Greece, and an upper premolar from Azmaka, Bulgaria.

Using computer tomography, they visualized the internal structures of the specimens and demonstrated that the roots of premolars are widely fused.

“While great apes typically have two or three 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 including Ardipithecus and Australopithecus,” Prof. Böhme said.

“The lower jaw of Graecopithecus freybergi has additional dental root features, suggesting that the species 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 co-author Jochen Fuss, a PhD student at the University of Tübingen.

“Furthermore, Graecopithecus freybergi is several hundred thousand years older than the oldest potential pre-human from Africa, the 6-7 million-year-old Sahelanthropus tchadensis from Chad.”

The team 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 and 7.175 million years before present.

“This dating allows us to move the human-chimpanzee split into the Mediterranean area,” Prof. Begun said.

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

“The findings call into question one of the most dogmatic assertions in paleoanthropology since Charles Darwin, which is that the human lineage originated in Africa,” Prof. Begun said.

As with many animals, the evolution of pre-humans may have been driven by dramatic environmental changes.

Prof. Böhme and co-authors demonstrated that the Sahara desert originated more than 7 million years ago.

They concluded this based on geological analyses of the sediments in which the two fossils were found.

“These data document for the first time a spreading Sahara 7.2 million years ago, whose desert storms transported red, salty dusts to the north coast of the Mediterranean Sea. This process is also observable today,” the authors said.

The researchers further showed that, contemporary to the development of the Sahara in North Africa, a savannah biome formed in Europe.

Using a combination of new methodologies, they studied microscopic fragments of charcoal and plant silicate particles, called phytoliths.

Many of the phytoliths identified derive from grasses and particularly from those that use the metabolic pathway of C4-photosynthesis, which is common in today’s tropical grasslands and savannahs.

The global spread of C4-grasses began eight million years ago on the Indian subcontinent — their presence in Europe was previously unknown.

“The phytolith record provides evidence of severe droughts, and the charcoal analysis indicates recurring vegetation fires,” Prof. Böhme said.

“In summary, we reconstruct a savannah, which fits with the giraffes, gazelles, antelopes, and rhinoceroses that were found together with Graecopithecus freybergi,” said co-author Professor Nikolai Spassov, from the Bulgarian Academy of Sciences.

“The incipient formation of a desert in North Africa more than seven million years ago and the spread of savannahs in Southern Europe may have played a central role in the splitting of the human and chimpanzee lineages,” Prof. Böhme said.

“We call this hypothesis the North Side Story, recalling the thesis of Yves Coppens, known as East Side Story.”

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J. Fuss et al. 2017. Potential hominin affinities of Graecopithecus from the Late Miocene of Europe. PLoS ONE 12 (5): e0177127; doi: 10.1371/journal.pone.0177127

M. Böhme et al. 2017. Messinian age and savannah environment of the possible hominin Graecopithecus from Europe. PLoS ONE 12 (5): e0177347; doi: 10.1371/journal.pone.0177347