Wednesday, June 7, 2017
The origins of modern humans pushed back to 300,000 years
A Griffith University geochronologist's state-of-the-art dating methods push back the origins of our species by an unprecedented 100,000 years, uncovering the oldest modern human and our deep biological history in Africa.
Professor Rainer Grün, director of the leading Australian Research Centre for Human Evolution (ARCHE), was among an international research team that dated fossils discovered at the archaeological site of Jebel Irhoud, Morocco.
The finds - reported on the front cover of Nature - are dated to about 300,000 years ago and represent the oldest securely aged fossil evidence of our own species.
Professor Grün said the fossils - which comprise skulls, teeth, and long bones of at least five individuals - revealed a complex evolutionary history of mankind that likely involved the entire African continent.
Jebel Irhoud has been well known since the 1960s for its human fossils and its Middle Stone Age artefacts but the interpretation of the Irhoud hominins has long been complicated because of persistent uncertainties surrounding their geological age.
Professor Grün used two dating methods - U-series and electron spin resonance - to accurately determine the age of Irhoud.
"The dating techniques I developed, currently being used at Griffith University, ensure minimal damage of the fossils but the process is very difficult to carry out," he said.
The crania of modern humans living today are characterised by a combination of features that distinguish us from our fossil relatives and ancestors - a small and gracile face, and globular braincase.
The fossils from Jebel Irhoud display a modern-looking face and teeth, and a large but more archaic-looking braincase.
"If we look at the history of human evolution, until the mid-80s it was thought model humans evolved in Africa and shortly after migrated to Europe at around 40,000 years," Professor Grün said.
"In the late 80s there were the first results of anatomically modern humans in Israel at about 100,000 years. In the 90s there were a few sites found in Ethiopia dated to 200,000 years and now with these results the origins of modern humans are further pushed back to 300,000 years."
Professor Grün said uncovering more about our history was hard because of the difficulty continuing to find fossilised human remains.
"When modern humans come to Europe they didn't bury the dead. So there are only two or three fossils that document the arrival of modern humans in Europe some 45,000 ago. In contrast, Neanderthals buried their dead but they ate them as well, leading to bone accumulations in caves" he said.
"The finds in Jebel Irhoud are one of the few places we've found modern skulls. That's why our understanding of human evolution is very patchy because we find so few human remains.
"We now have to rethink a number of principles within human evolution. This shows our species has a very deep history in Africa."
The work is the latest in a series of important scientific papers recently published by members of ARCHE, in which the role of dating studies were crucial. These include the fossilised bones of the Stone Age victims unearthed at Nataruk (Kenya), the discovery of prehistoric art and ornaments from the Indonesian 'Ice Age' and the origin of 'hobbits' found in Flores Island.
Professor Grün said these works highlighted the increasing role ARCHE played in understanding human origins and added to Griffith's reputation as becoming one of the world's leading institutions in Quaternary Geochronology.