The team of worldwide researchers led by the Max Planck Institute for the Science of Human History was conducting archaeological fieldwork in the Nefud Desert of Saudi Arabia when they came across the striking fossil.
It remains unclear whether the Homo sapiens at Al Wusta arrived via the Levant, by crossing the Red Sea or by going around the Red Sea's southern end - an idea supported by Donald Henry from the University of Tulsa in an accompanying article.
Study co-researcher Iyad Zalmout, a paleontologist with the Saudi Geological Survey, found the remarkable 1.3-inch-long (3.2 centimeters) fossil finger in the Nefud Desert in 2016, said study lead researcher Huw Groucutt, an archaeologist at the University of Oxford in England.
The researchers say the discovery puts a spotlight on Saudi Arabia as the region could lead to even more exciting discoveries relating to our early ancestors and their first steps out of Africa.
The findings, published this week in the journal Nature Ecology & Evolution, are just the latest to lend further complexity to the story of human evolution and migration. It seems humans lived in this area over 100,000 years ago. Then they compared that shape with dozens of finger bones from humans, non-human primates and extinct hominid species.
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.
Oddly enough, researchers have identified fewer human fossils in this second phase than in the much earlier first phase.
Genetic studies suggest that non-Africans today are descended from modern humans who walked out of Africa up to 60,000 years ago, with earlier migrants dying out - possibly due to the impact of Neanderthals, or being overwhelmed by further waves of our own species.
Huw Groucutt of the University of Oxford in the United Kingdom and his colleagues found the finger bone at a site called Al Wusta in what is now the Nefud Desert.More news: LG G7 ThinQ Name Confirmed, Phone Launching On May 2
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The age of the fossil was dated using a technique called uranium series dating, which involves etching microscopic holes in the fossil with a laser and measuring the ratio between tiny traces of radioactive elements.
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.
Prior to this discovery, it was thought that early migration into Eurasia remained restricted to the Mediterranean forests of the Levant, on the doorstep of Africa. This would make it the oldest human fossil found outside Africa and the Levant.
The Al Wusta site in Saudi Arabia's Nefud Desert is a dry, arid place today, but it sat on the lush banks of a lake 88,000 years ago. The analysis showed that that bone was about 87,600 years old, give or take 2,500 years.
"All of these studies agreed that the fossil belonged to Homo sapiens", Groucutt said at the news conference.
Where does the Al Wasta finger bone fit into all of this?
The finger bone wasn't the only find at the site.
This new finding is one of many that are helping scientists map early humans' trek out of Africa.