“What I was surprised by was how well this new discovery fits into the new picture that’s emerging of the evolution of Homo sapiens,” said Julia Galway-Witham, a research assistant at the Natural History Museum in London who wrote an accompanying perspective article.
Dr. Hawks and other researchers advised caution in interpreting the discovery. Although this ancient person may have shared some anatomical characteristics with present-day people, this “modern human” would have probably looked much different from anyone living in the world today.
“Early modern humans in many respects were not so modern,” said Jean–Jacques Hublin, director of the department of human evolution at the Max Planck Institute for Evolutionary Anthropology in Germany.
Dr. Hublin said that by concluding the jawbone came from a “modern human,” the authors were simply saying that the ancient person was morphologically more closely related to us than to Neanderthals.
That does not mean that this person contributed to the DNA of anyone living today, he added. It is possible that the jawbone belonged to a previously unknown population of Homo sapiens that departed Africa and then died off.
That explanation would need to be tested with DNA samples, which are difficult to collect from fossils found in the arid Levant.
The upper jawbone, or maxilla, was found by a team led by Israel Hershkovitz, a paleoanthropologist at Tel Aviv University and lead author of the new paper, while excavating the Misliya Cave on the western slopes of Mount Carmel in Israel. The jawbone was discovered in 2002 by a freshman on his first archaeological dig with the group.
The team had long known that ancient people lived in the Misliya Cave, which is a rock shelter with an overhanging ceiling carved into a limestone cliff. By dating burned flint flakes found at the site, archaeologists had determined that it was occupied between 250,000 to 160,000 years ago, during an era known as the Early Middle Paleolithic.
Evidence, including bedding, showed that the people who lived there used it as a base camp. They hunted deer, gazelles and aurochs, and feasted on turtles, hares and ostrich eggs.
Dr. Hershkovitz and Mina Weinstein-Evron, an archaeologist at the University of Haifa, felt that the jawbone looked modern, but they needed to confirm their hunch.
Dr. Hershkovitz has made similar findings in the past. In 2015, he announced finding a 55,000-year-old skull in the Levant. But a 2010 discovery of 400,000-year-old teeth in Israel in which he participated received criticism for how it was reported in the media.
To test their suspicions about the jawbone, the archaeologists sent the specimen on a world tour. “It looked so modern that it took us five years to convince people, because they couldn’t believe their eyes,” said Dr. Weinstein-Evron.
One of the first stops was Austria, home to a virtual paleontology lab run by Gerhard W. Weber, a paleoanthropologist at the University of Vienna. There scientists were able to assess whether the bone belonged to a modern human or a Neanderthal, which are thought also to have occupied the region during that time period.
Using high resolution micro-CT scanning, Dr. Weber created a 3D replica of the upper left maxilla that allowed him to investigate its surface features and, virtually, to remove enamel from the teeth.
He then performed a morphological and metric test that compared the Misliya fossil with about 30 other specimens, including fossils of Neanderthals, Homo erectus, more recent Homo sapiens, and other hominins that lived in the Middle Pleistocene in Asia, Africa Europe and North America.
“The shape of the second molar, the two premolars and the whole maxilla are very modern,” said Dr. Weber.
The tests also found that the base of the cheek bone was located above the first molar, the incisors lacked a shovel shape, and the premolars were high and narrow, all characteristics found in modern humans and not Neanderthals.
“It’s not a little bit modern, or on the border of being modern,” he said. “It is really modern human.”
“It looks like they’ve done a really thorough study of the morphology of the maxilla and determined it’s not a Neanderthal,” said Melanie L. Chang, an anthropologist from Portland State University who was not involved in the study. “I believe them.”
Next, the archaeologists determined the jawbone’s age by performing three dating techniques in Australia, France and Israel.
“The dating had to be rock solid,” said Rolf M. Quam, an anthropologist at Binghamton University in New York and an author of the paper. The team dated the tooth dentin and enamel, the sediment stuck to the upper jaw, and tools found near the fossil.
“I don’t know how much more we could do with this little bone,” said Dr. Quam. “I think we’ve squeezed blood from a turnip here.”
Together, the techniques put the jawbone at between 177,000 and 194,000 years old, in line with what was already known about the period during which the cave was inhabited.
“This thing is as old as we thought it was, and it was probably the earliest Homo sapien out of Africa ever found,’” said Dr. Quam. “It’s not very often you can make a superlative statement, but in this case we can.”
The Misliya finding is just the latest in a series of discoveries that are changing the story of our evolutionary past. One study, not yet confirmed, suggested that modern humans may have interbred with Neanderthals in Eurasia about as far back as 220,000 years ago.
If so, that would mean that at least some modern humans migrated from Africa far earlier than previously thought. Indeed, early humans may have made multiple journeys through the Levant corridor.
“We are now realizing that it was not one big exodus out of Africa in a given time period,” said Dr. Hershkovitz. “Rather, there was a flow of hominins coming in and out of Africa for at least the last half a million years.”