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.Traditionally researchers built timelines of human prehistory based on fossils and artifacts, which can be directly dated with methods such as radiocarbon dating and Potassium-argon dating.However, these methods require ancient remains to have certain elements or preservation conditions, and that is not always the case.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.
When scientists say that modern humans emerged in Africa about 200,000 years ago and began their global spread about 60,000 years ago, how do they come up with those dates?
Moreover, relevant fossils or artifacts have not been discovered for all milestones in human evolution.
Analyzing DNA from present-day and ancient genomes provides a complementary approach for dating evolutionary events.
“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.