"This find, together with other finds in the last few years, suggest that modern humans, Homo sapiens, are moving out of Africa multiple times during many windows of opportunity during the last 100,000 years or so", he said. "They earned this find the old-fashioned way: hard work". Genetic studies show that humans may have made it to Eastern Asia as early as 80,000 years ago. But 90,000 years ago, there would have been a large river and an extensive fertile area that welcomed plants, animals and even humans.
"The Arabian Peninsula has always been considered to be far from the main stage of human evolution", said senior author Professor Michael Petraglia, from the Max Planck Institute for the Science of Human History.
"It's become increasingly clear that humans dispersed far out of Africa and the Levant before 60,000 years ago, a date suggested by genetics".
The single fossil finger bone of Homo sapiens - pictured from various angles - from the Al Wusta site, Saudi Arabia is pictured in this undated handout composite photo obtained by Reuters April 9, 2018.
Surveying the site in the Nefud Desert, Saudi Arabia. The ancient lake bed (in white) is surrounded by sand dunes of the Nefud Desert. 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.
"He picked up the bone", Petraglia recalled, "and he immediately recognized it as human. "That night back at the hotel, we were Googling 'human finger bone" and, yeah, it looked like our species". Professional anatomists analyzed 3D scans of the bone and concluded that it was a match for our own species, rather than another early hominins such as Neandertals or a member of Australopithecus.
Using a technique called uranium series dating, a laser was used to make microscopic holes in the fossil and measure the ratio between tiny traces of radioactive elements, they said.
A report on the work was published Monday in the journal Nature Ecology & Evolution.
"With the finding in Al Wusta, I would say that presence of Homo sapiens in Asia before 50,000 to 60,000 years ago is out of doubt, and we can now move on to the next questions: how and why modern humans left Africa and why they took so long to enter Europe", she said. Crucially, said Groucutt, these stone tools were of an "old-fashioned" type, countering the idea that human migration beyond the Levant was driven by our species developing better technology, with evidence of an ancient lake highlighting that the dispersal was at least partly driven by a changing climate.
John Hawks, a paleoanthropologist at the University of Wisconsin in Madison, says the authors have convincingly shown the finger bone is likely a hominin of some sort. During this period they scoured the region for signs of early humans, seeing it as a natural "stepping stone" for humans leaving Africa.
The team recognised the bone as human on sight, and later confirmed this by comparing it to finger bones of other humans, extinct hominins like Neanderthals, and other primates such as gorillas.