"But now, with the fossil finger bone from the site of Al Wusta in Saudi Arabia, we have a find that's 85,000 to 90,000 years old, which suggests that Homo sapiens is moving out of Africa far earlier than 60,000 years ago", Petraglia told reporters at a news conference. Now, they may have it.
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. "They earned this find the old-fashioned way: hard work".
This 85,000-year-old fragment, however, has just helped to revolutionise our understanding of early human history because it should not have been in Arabia for another 25,000 years. Following the fossil's discovery in 2016, the scientists spent two years subjecting it to rigorous tests determining its age and confirming that it did, indeed, belong to a member of the Homo sapiens species. It is also the first ancient human fossil from the Arabian Peninsula. Others have argued there were several migrations in and out of Africa throughout this whole period.
This new finding is one of many that are helping scientists map early humans' trek out of Africa.
'We know that shortly after they lived, the rains failed and the area dried up.
The single fossil finger bone of Homo sapiens - pictured from various angles - from the Al Wusta site, Saudi Arabia.
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In 2014, they discovered a site named Al Wusta in Saudi Arabia's arid Nefud Desert that once sat on the banks of a large freshwater lake. 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.
"But here we've dated both the deposits and the fossil finger bone directly", Petraglia said.
The object in question is a fossilized piece of a bone, probably the middle portion of a middle finger.
A basic visual examination suggested it belonged to Homo sapiens, Groucutt said. Researchers bored a microscopic hole into it with a laser and measured traces of radioactive elements within. When the bone was buried, it absorbed uranium, which can be measured and provide a minimum age estimate.
The global team published its findings in the journal Nature Ecology & Evolution.
The team found fossils of animals, including hippos, as well as advanced stone tools.
"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.
This finger wasn't just an interesting find in its own right. If ancient humans could leave one environment for the other, they must have been quite adaptable, the researchers said.