A Jawbone Is the Oldest Modern-Human Fossil Outside of Africa

Between 1929 and 1934, the legendary British archaeologist Dorothy Garrod excavated a series of caves and rock shelters on the slopes of Israel’s Mount Carmel. Within those caves, she uncovered a series of historically important hominid fossils. Some were Neanderthals. Others belonged to early modern humans—Homo sapiens. Among the latter, skeletons of 10 individuals from one cave, Skhul, turned out to be between 80,000 and 120,000 years old, making them among the oldest fossils of modern humans outside of Africa—the continent where we originated.

But another cave, Misliya, escaped Garrod’s attention. It had collapsed at least 160,000 years ago, and “was never excavated or touched,” says Israel Hershkovitz, from Tel Aviv University. “It was protected and sealed by big stone slabs.”

It took a year for a team, led by Hershkovitz and Mina Weinstein-Evron, from the University of Haifa, to remove the slabs. When they started excavating the cave proper, they found a bountiful haul of animal bones, burned objects, tools, and, eventually, an upper jawbone, complete with eight teeth.

After more than a decade of work, the team has now confirmed that the Misliya jaw belonged to a modern human, and that it is even more ancient than the Skhul remains. At somewhere between 177,000 and 194,000 years old, it now holds the record for the earliest modern-human fossil outside Africa. It tells us that our species must have ventured beyond our birth continent far earlier than other fossils had suggested.

That’s not unexpected, though. Many lines of evidence show that early humans probably dispersed from Africa on several occasions, encountering other hominids like Neanderthals and Denisovans who had already established themselves in the wider world. These groups all had sex, leaving traces of their DNA in each other’s genomes. And based on these exchanges, geneticists have estimated that some humans must have been living beyond Africa by 220,000 years ago or more. If that’s the case, there must have been fossils outside the continent that were older than the Skhul specimens. It was just a matter of finding them.

“The Misliya fossil is significant because it is the first finding that conclusively shows that early modern-human population expansions out of Africa actually did occur even before the Skhul episode,” says Katerina Harvati, from the University of Tübingen.

Once Hershkovitz and Weinstein-Evron discovered the jawbone, they had two challenges. First, they had to identify it. Several other hominids, like Neanderthals, were living in the same region at the time, but the team determined that the jaw and teeth had none of the characteristic traits of these other groups. Instead, its features were clearly those of modern humans. “It is Homo sapiens par excellence,” says Hershkovitz. “It’s a modern human, like you or me, more or less.”

Next, the team had to date the specimen. They used three techniques, each performed by different labs working independently in separate countries. An Australian team analyzed burned flint tools that were found near the fossils, concluding that they are 179,000 years old. An Israeli team measured radioactive isotopes of uranium in the rocky sediment attached to the teeth, estimating that the fossil's minimum age is somewhere between 177,000 and 193,000 old. And a Spanish team analyzed the enamel on one of the teeth, showing that it has a maximum age of 194,000 years.

“Each lab did a different analysis without knowing the results of the other labs,” says Hershkovitz. “Amazingly, they all came more or less with the same numbers. The dates are more secure than for any other fossil I know of.”

These dates don’t imply that humans have lived continuously in the Levant for at least 180,000 years, or that the Misliya residents were the direct ancestors of those who eventually lived in Skhul. At the time, the region had a variable climate, with humid phases punctuated by droughts. Rather than being a permanent sanctuary for migrating humans, it could have been what some anthropologists have called a “boulevard of broken dreams”—a place where humans regularly ventured into, but rarely stayed permanently. The Misliya jaw simply suggests when those migration attempts might have begun.

“The research is solid,” says Shara Bailey from New York University, who specializes in ancient hominin teeth. “Is it the earliest modern human outside of Africa? I think that’s probably true. But it’s perhaps unsurprising, given that we now know that Homo sapiens was in Africa even earlier than we had thought.”

Until recently, the earliest specimens of modern humans were two Ethiopian fossils that are 160,000 and 195,000 years old, respectively. But last year, Bailey and others reported the discovery of 315,000-year-old bones from a Moroccan cave called Jebel Irhoud. “If Homo sapiens is in Africa 300,000 years ago, it’s not that surprising that they made excursions out of Africa,” she says.

The Jebel Irhoud specimens had an interesting mishmash of features, however. Their faces looked modern, but the backs of their heads were flatter on top and longer at the back than ours. That’s why Hershkovitz isn’t convinced that they were modern humans at all. To him, the Misliya find is not just the earliest modern-human fossil outside Africa, but the earliest modern-human fossil, full stop.

It’s a bold claim to base on a single jawbone, especially since several recently discovered hominids like Homo naledi and Australopithecus sediba have unexpected combinations of physical traits. “We can’t make assumptions about what the rest of the hominin looked like without seeing the rest of the remains,” says Bailey. “I don’t doubt that these are Homo sapiens, but if we found a teeny brain with the rest of the [jaw], would that change the picture? That’s been happening a lot lately.”

The stone tools found in Misliya add another wrinkle to the story. These were made with a sophisticated method called the Levallois technique, which was also used to make tools found at Jebel Irhoud. Perhaps this means that the technique is a signature of early modern humans, who used it to manufacture tools as they spread around Africa and beyond.

“What is clear is that we do not have the whole story yet,” says Harvati, “but Misliya is a crucial piece of the puzzle.”