For more than a decade, a team of archaeologists and anthropologists scoured the Arabian Desert for evidence that some of the earliest members of our species once traversed these formerly green lands.
Palaeontologist Julien Louys from Griffith University said the discovery showed that modern humans were out of Africa and the nearby Levant region by about 85,000 or 90,000 years ago.
"Our study shows that the early spread of our species was aided by climate change and that humans spread into very diverse types of habitats as they moved beyond Africa", Huw Groucutt, an archaeologist from the University of Oxford and lead author on the paper, said at a media briefing.
An worldwide research team, including Oxford University scientists and the Saudi Commission for Tourism and National Heritage, has been scouring the region's ancient lake beds for signs of what life was like tens of thousands of years ago. The ancient lake bed (in white) is surrounded by sand dunes of the Nefud Desert.
"This discovery for the first time conclusively shows that early members of our species colonized an expansive region of southwest Asia and were not just restricted to the Levant", said lead author Dr. Huw Groucutt, from the University of Oxford in the United Kingdom and the Max Planck Institute for the Science of Human History in Germany.
It indicates that early human migrations may have happened more frequently than previously thought, and that our ancestors may have gone to regions scientists hadn't suspected.
"The Arabian Peninsula has always been considered to be far from the main stage of human evolution", said Michael Petraglia, a professor at the Max Planck Institute for the Science of Human History in Germany.
"This discovery for the first time conclusively shows that early members of our species colonized an expansive region of southwest Asia and were not just restricted to the Levant", Groucutt said in a statement. Their hunch paid off 2 years later, when study co-author and paleontologist Iyad Zalmout of the Saudi Geological Survey in Jeddah found a small bone stuck in the sediment. It is the second bone in from the fingertip, but it's not clear which finger.
"He picked up the bone", Petraglia recalled, "and he immediately recognized it as human".
Using a technique called uranium series dating, the fossil was found to be up to 90,000 years old. Researchers bored a microscopic hole into it with a laser and measured traces of radioactive elements within.
A report on the work was published Monday in the journal Nature Ecology & Evolution. "Still, I doubt whether anyone can identify a single isolated finger bone as a modern human, as opposed to any other form of hominin", such as Neandertal, he says.
According to one mainstream theory, humans left Africa in a single wave, moving along the coast from Africa via southern Arabia and India all the way to Australia. They also raise questions about how long these early migrants' descendants lived on.