The results conclusively showed that the finger bone, the first ancient human fossil found in Arabia, belonged to our own species.
In the Nefud Desert of Saudi Arabia, researchers have found the oldest remains from early humans outside of Africa and the nearby Mediterranean Levant region. Other dates obtained from associated animals fossils and sediments converged to a date of approximately 90,000 years ago.
A fragment of a human finger bone dating back up to 90,000 years has been found in the Saudi Arabian desert - and it could rewrite the history of mankind's journey out of Africa.
In recent years, however, this outlook has been challenged by findings in Israel's caves that suggest humanity began to take its first tentative steps out of Africa far earlier.
The ancient fossils ever found was 120,000 years old, found in China but their human origin was not dated precisely so far. The discovery, described in Nature Ecology and Evolution, is the oldest directly dated Homo sapiens fossil outside of Africa and the Levant and indicates that early dispersals into Eurasia were more expansive than previously thought.
For example, for years, we thought Homo sapiens evolved from Homo erectus in Africa 200,000 years ago-but then in 2017, scientists found bone evidence in Morocco suggesting humans may have been around as long as 300,000 years ago.
In 2016 their colleague Iyad Zalmout, an archaeologist with the Saudi Geological Survey and author on the paper, was prospecting in a site called Al Wusta in the Nefud Desert in the northern part of the Arabian Peninsula.
While the Nefud Desert is now a veritable sea of sand, it was hospitable when this individual lived - a grassland teeming with wildlife alongside a freshwater lake. He couldn't immediately tell whose this bone was and from where it had come.
To determine how old the bone was, the team sent it to Rainer Grün, a dating specialist at Griffith University in Australia, who had previously helped date a 180,000-year-old jawbone from an Israeli cave. It is the second bone in from the fingertip, but it's not clear which finger.
There have been multiple dispersions of human beings out of Africa, the migratory movement and colonization of Eurasia have been much more complicated than our textbooks say. "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.
"And that makes sense when you think these guys are making [and using] stone tools so they're really using their hands to do a lot of hard, manual labour".
Katerina Harvati, a paleoanthropologist at the University of Tübingen in Germany, agrees, noting there's so much anatomical overlap between hominin species that she'd like to see additional fossils confirm it. If ancient humans could leave one environment for the other, they must have been quite adaptable, the researchers said. They also raise questions about how long these early migrants' descendants lived on.