According to an international research team led by Professor Madelaine Böhme and Professor Nikolai Spassov, the common lineage of great apes and humans likely split several hundred thousand years earlier than we originally believed. After studying two fossils of Graecopithecus freybergi, the pair concluded that the split of the human lineage probably occurred in the Eastern Mediterranean, not in Africa.
It’s relatively common knowledge that present-day chimpanzees are our closest living relatives, but where the last chimp-human common ancestor lived is a topic of hot debate. Until now, researchers have widely believed that the lineages diverged five to seven million years ago as the first pre-humans developed in Africa.
The team analyzed a lower jaw from Greece and an upper premolar from Bulgaria from the fossil hominid Graecopithecus freybergi. Using computer tomography, the team visualized the internal structures of the fossils and revealed that the roots of the 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”, said Böhme.
The lower jaw, named ‘El Graeco,’ also has additional dental root features that suggest the species could be pre-human—surprising results as humans were previously known from sub-Saharan Africa. Adding to the puzzle, Graecopithecus is several hundred thousand years older than the oldest potential pre-human from Africa.
“This dating allows us to move the human-chimpanzee split into the Mediterranean area,” Professor David Begun of the University of Toronto added.
Scientists believe the evolution of pre-humans was likely driven by dramatic environmental changes. To support this point, the team demonstrated that the North African Sahara desert originated more than seven million years ago, using an analysis of sediments in which the two fossils were found. The dusty sediment had a high content of different salts, and modeling revealed that the amount of dust coming from the Sahara to the north coast was more than tenfold what we see today.
According to phys.org:
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,” said Böhme. “In summary, we reconstruct a savannah, which fits with the giraffes, gazelles, antelopes, and rhinoceroses that were found together with Graecopithecus,” Spassov added.
“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,” said Böhme.
Source: phys.org, evolutionnews.org