A middle finger might change what we thought we knew about human migration from Africa. As Gizmodo reports, a new study in Nature Ecology and Evolution analyzes what may be the oldest modern human fossil outside of Africa and the Levant (modern-day Israel, Lebanon, Syria, and Jordan). Found in an ancient lake bed in the Arabian desert, the bone has been dated to 88,000 years ago, indicating that human migration from Africa may have started much earlier than previously thought.
Previous research has suggested that Homo sapiens populations migrated out of Africa and into Eurasia (perhaps thanks to climate change) in one big wave around 60,000 years ago. The fossilized finger bone, about an inch long, indicates the story might be more complicated.
A paleontologist with the Saudi Geological Survey, Iyad Zalmout, found the bone in 2016. He and his fellow researchers created 3D scans of the bone and compared them with other finger bones from Homo sapiens, Neanderthals, and modern primates like gorillas to determine that it is, in fact, a human bone. They then dated the fossil using uranium series dating, a measure of the bone's ratio of radioactive elements, to arrive at an estimated age of roughly 88,000 years old. They also found animal fossils and sediment at the site to be around 90,000 years old.
At that time, the area in the Nefud Desert where the bone was found would have been semi-arid grasslands surrounding a freshwater lake, a more hospitable climate than it is today. At some parts during this era, the Red Sea between Africa and the Arabian Peninsula would have been low enough to make it essentially just a big river, so humans could have crossed there, as a related article in the journal by anthropologist Donald Henry notes.
Several scientists told Gizmodo that it's possible that the bone isn't human at all—it could belong to a relative of Homo sapiens—and that the authors of the new study are overstating the significance of their finding, so the analysis is somewhat controversial.
However, other evidence has pointed to an earlier African exit date for humans. In 2015, scientists in China discovered human teeth they dated to 80,000 years ago, though they weren't able to date the bone directly—instead, they analyzed the teeth's surroundings. In January 2018, scientists announced that they had found a partial jawbone in an Israeli cave dating back at least 177,000 years.
"The ability of these early people to widely colonize this region [of Arabia] casts doubt on long held views that early dispersals out of Africa were localized and unsuccessful," said lead author Huw Groucutt, of the University of Oxford and the Max Planck Institute for the Science of Human History, in a statement.