A basic visual examination suggested it belonged to Homo sapiens, Groucutt said.
Playing a vital role in the excavation of the finger bone, Griffith University palynologist Dr Julien Louys helped locate and identify the fossil at the dig site, while ARCHE's head of research Professor Rainer Grün, was the one responsible for calculating the age of the mysterious find at his Australian laboratory.
However, there are doubts about many of discoveries, including those from China and Australia, said the authors of Monday's study.
"It really challenges that idea that humans only left 60,000 years ago", he said.
In order to confirm that the fossil was human and not Neanderthal or another relative species, the researchers scanned the fossil in three dimensions.
Although some say it's hard to identify our species, Homo sapiens, by a single bone, the findings appear unimpeachable, says John Shea, an anthropologist at the State University of NY in Stony Brook who studies human origins, but wasn't involved in the study.
The team had been searching the Saudi Arabian desert for more than 10 years without finding human fossils.
Researchers say it shows hunter-gatherers had reached that area by 85,000 years ago.
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Al Wusta may be a desert now, but about 85,000 years ago, it had a freshwater lake frequented by many animals, including hippopotamuses, Pelorovis (a now-extinct genus of wild cattle) and Kobus (a genus of African antelope), whose fossilized remains were found at the site.
The disclosure is the most seasoned specifically dated Homo sapiens fossil outside of Africa and the promptly neighboring Levant, and shows that early dispersals into Eurasia were more extensive than already thought.
They were able to date the bone directly, using precise techniques that rely on the decay of radioactive uranium. Hundreds of animal fossils were found at the site, including those belonging to hippopotamus, as well as plenty of stone tools made by humans.
"This discovery for the first time conclusively shows that early members of our species colonised an expansive region of southwest Asia and were not just restricted to the Levant", said Huw Groucutt from the University of Oxford in the UK.
The outcomes definitively demonstrated that the finger bone, the principal antiquated human fossil found in Arabia, had a place with our own particular species. "He said, "This is a human finger, '" Groucutt recalls".
It was an intermediate phalanx, the bone between a fingertip and finger knuckle.
The finding indicates modern humans travelled to follow kinder climates, but they did not stay indefinitely. They also raise questions about how long these early migrants' descendants lived on. "That night back at the hotel, we were Googling 'human finger bone" and, yeah, it looked like our species".
"Tracing the evolution and geographic dispersal of the human lineage is rather like connecting pitifully few dots on a vast three-dimensional grid of time and space", Donald O. Henry, an anthropologist from the University of Tulsa, wrote in an article published alongside the new study.