May 22, 2017

Pre-Human Fossils Suggest Mankind Emerged From Europe Rather Than Africa

Illustration of ‘El Graeco,’ foreground, living in a savannah environment in the Eastern Mediterranean 7.2 million years ago.
When an ancient, toothy lower jaw was found in 1944 in Pyrgos Vassilissis, Greece, few paid much attention to the fossil. World War II was still underway, so the discovery was largely overlooked by all but the most ardent anthropologists. Even Pyrgos Vassilissis, a former royal estate on the Greek mainland, is often bypassed by travelers on their way to bustling Athens.

Interest in both the fossil and Pyrgos Vassilissis may soon grow, however, owing to the announcement of an explosive finding by an international team of researchers. In a paper published in the journal PLOS ONE, the scientists outline how the jaw likely belonged to the earliest known hominin, or pre-human — providing evidence that the last common ancestor of chimps and humans lived in the Eastern Mediterranean.

A second paper describes what this region’s climate was like during the lifetime of the human-ish species, Graecopithecus freybergi, otherwise known informally as “El Graeco.” Taken together, the findings support the idea that regal Pyrgos Vassilissis lies within the site where humanity first evolved 7.2 million years ago.

Project leader Madelaine Böhme of the Senckengberg Center for Human Evolution and Paleoenvironment at the University of Tübingen, co-author Nikolai Spassov from the Bulgarian Academy of Sciences, and their colleagues analyzed both the Pyrgos fossil and a related upper premolar tooth unearthed in Azmaka, Bulgaria.

The lower jaw of the 7.2-million-year-old Graecopithecus freybergi (El Graeco) from Pyrgos Vassilissis, Greece.
“El Graeco is the oldest known potential hominin,” Spassov said. He is several hundred thousand years older than the oldest potential pre-human from Africa: 6–7-million-year-old Sahelanthropus from Chad.

Anthropologists use the term hominin, or pre-human, because the last common ancestor of humans and chimps clearly retained both non-human primate and human characteristics. Although El Graeco is only known from the fossil jaw and premolar, Böhme and her team could see how these features were evolving into more human-like forms. Computer tomography visualized the internal structures of the fossils and found that the roots of the premolars were widely fused.

“While great apes typically have two or three separate and diverging roots,” Böhme said in a statement, “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.”

“No other fossil and living non-human primate is known with such roots,” Spassov said, adding that the analysis of El Graeco’s environment determined that it was a savannah when this individual was alive.

A 7.2-million-year-old upper premolar of Graecopithecus from Azmaka, Bulgaria.
The researchers studied microscopic fragments of charcoal and plant silicate particles, called phytoliths, to reconstruct what the past climate was like both in the Eastern Mediterranean and North Africa.

“The phytolith record provides evidence of severe droughts, and the charcoal analysis indicates recurring vegetation fires,” Böhme said. “In summary, we reconstruct a savannah, which fits with the giraffes, gazelles, antelopes, and rhinoceroses that were found together with Graecopithecus.”

The scientists further studied salts as well as uranium, thorium, and lead isotopes discovered in dust particles originating from the Sahara Desert and that are often transported during storms to the Mediterranean. Dating of these materials, and analysis of their spread, suggests that the Sahara originated around 8–7 million years ago.

Electron microscope image of a dust particle rounded by wind transport. It originated in the Sahara Desert and was found in 7.2-million-year-old sediments in Greece.
“The incipient formation of a desert in North Africa more than 7 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,” Böhme said.

The theory is now called the North Side Story, recalling a hypothesis made by anthropologist Yves Coppens, co-discoverer of the famous hominin “Lucy.” Coppens’ theory, known as the East Side Story, holds that pre-humans first evolved in Kenya’s Rift Valley.

Read more at Discovery News

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