Newly discovered pre-human remains dated to more than seven million years ago could change common assumptions about the origins of humanity, suggesting that people may have diverged from great apes hundreds of thousands of years earlier than experts had previously thought.
In fact, in a pair of studies published this week in the journal PLOS One, an international team of scientists reported that they had not just discovered fossil evidence of what they believe might be the oldest hominid ever, but possible proof that humans split from their great ape ancestors in the Eastern Mediterranean, not in Africa, as researchers had long hypothesized.
The team, led by Professor Madelaine Böhme of the Senckenberg Centre for Human Evolution and Palaeoenvironment at the University of Tübingen in Germany and Professor Nikolai Spassov of the Bulgarian Academy of Sciences, studied Graecopithecus fossils discovered in Greece and Bulgaria, and determined that they belonged to pre-humans.
Previous studies have suggested that the last common ancestor of humans and chimpanzees, their closest living relatives, lived in Africa between five and seven million years ago. However, in the new study, the researchers used computer tomography technology to analyze the lower jaw and upper molar of the Graecopithecus hominids. They found that the roots of the molar were widely fused – “a feature that is characteristic of modern humans, early humans, and several pre-humans including Ardipithecus and Australopithecus,” Böhme explained in a statement.
Findings place the human-chimpanzee split in the Mediterranean Era
Specifically, Böhme’s team found that the roots of the Graecopithecus molar converge and were partially fused, unlike those of great apes, which typically have two to three separate roots which diverge. Furthermore, they found additional dental root features in the jaw, further indicating that the species known as Graecopithecus freybergi could be part of the pre-human lineage.
If that is indeed the case, the discovery is significant, as the new fossils are reportedly hundreds of thousands of years older than the currently oldest known possible pre-human, the six to seven million-year-old Sahelanthropus specimen from Chad, the researchers said. The sediment around the sites where the new fossils were discovered were dated to 7.175 and 7.24 million years ago.
“It is at the beginning of the Messinian, an age that ends with the complete desiccation of the Mediterranean Sea,” explained Böhme. “This dating allows us to move the human-chimpanzee split into the Mediterranean area,” added University of Toronto paleoanthropologist Professor David Begun, co-author of one of the two new PLOS One papers.
The researchers also analyzed the sediments in which the fossils were found, and discovered that they were similar in composition to those found in the Sahara desert, and that isotopes of lead, uranium, and thorium found in individual dust particles suggested that they were North African in origin and between 0.6 and 3.0 billion years old. The sum of the evidence suggests for the first time that the Sahara desert had been spreading 7.2 million years ago, and that storms caused the desert dust to be transported to the northern coast of the Mediterranean Sea.
Furthermore, they that a savannah was developing in Europe at around the same time, and that the record of microscopic charcoal and plant silicate particles (phytoliths) showed evidence of severe drought. Combined, these factors “may have played a central role in the splitting of the human and chimpanzee lineages,” Böhme concluded.
Image credit: Wolfgang Gerber/University of Tübingen