Ancient Finger Bone Discovery in Saudi Arabia Changes Human Migration Story

The dissemination of Homo sapiens to every corner of the Earth started when groups of anatomically modern humans left Africa thousands of years ago. The increased fossil finds and improved dating technology of recent years, however, keeps shifting our understanding of exactly when they left and where they went. And according to a Nature Ecology & Evolution study released Monday, a single finger bone is poised to shake it all up.

In the paper, experts in archeology and human evolution announced that a fossilized finger bone that was found in the Nefud Desert of Saudi Arabia is much older than most experts would expect it to be. They present evidence that it belonged to an early modern human who lived approximately 88,000 years ago — making it the oldest directly dated Homo sapiens fossil found outside of Africa and the Levant, a neighboring region. Finding a human fossil of that age in this region indicates that the journey early humans took out of Africa was more complicated than anyone previously believed, filled with more departures and more complicated routes.

“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,” lead author and Oxford University archaeologist Huw Groucutt, Ph.D., explained in a statement released Monday. “The ability of these people to widely colonize this region casts doubt on long-held views that early dispersals out of Africa were localized and unsuccessful.”

Before now, the Arabian Peninsula hasn’t really been considered a hotbed of human evolution findings. The new discovery changes that: At a desert site called Al Wusta, alongside fossils of hippopotamus and fresh-water snails suggesting that part of the desert was once an ancient lake, the team also found stone tools and, most importantly, a well-preserved, 3.2-centimeter-long fossil that looked a lot like a human finger. To confirm it really was a finger bone, they scanned it in three dimensions and compared its shape to the fingers of primates, Neanderthals, and other Homo sapien samples. It was definitely human.

The next step in the process was determining how old the finger really was. The team sent it to dating specialist Rainer Grün, Ph.D., who was part of the team that, in January, identified a human jaw bone found in Israel as the earliest modern human found outside of Africa. On the finger fossil, Grün used a technique called uranium-series dating, drilling microscopic holes with a laser in the fossil to measure the ratio between traces of radioactive elements.

At 88,000 years old, this finger is a game changer because scientists previously believed that humans only left the East Mediterranean Levant — the region where the jaw bone was found — between 60,000 to 50,000 years ago. This finding, the scientists write, “challenge this model” and show “early H. sapiens dispersals out of Africa were not limited to winter rainfall-fed Levantine Mediterranean woodlands immediately adjacent to Africa, but extended deep into the semi-arid grasslands of Arabia, facilitated by periods of enhanced monsoonal rainfall.”

In other words, climate change facilitated an inviting move over and out from the Levant — and from there onward humans were able to disperse, a scattering that led them to eventually meet other hominins like Neanderthals and Denisovans and mix up the gene pool in a way that’s reflected in our DNA today.