Researchers have found a 55,000-year-old partial skull in the northern Israel community of Manot, from about the time when modern humans expanded out of Africa.
The incomplete skull, which was discovered deep in a cave by amateur speleologists, may belong to a human group that interbred with Neanderthals. Filling a major gap in the fossil record of Homo sapiens' journey from Africa to Europe, the anatomy of this fossil may offer clues about what the first modern human Europeans were like.
The team that made the discovery includes Prof. Israel Hershkovitz of Tel Aviv University with archaeologists Dr. Ofer Marder of Ben-Gurion University's Department of Bible, Archaeology and Ancient Near East Studies, and Dr. Omry Barzilai of the Israel Antiquities Authority. They recently published their finding in the journal Nature.
Modern humans first arose between 150,000 and 200,000 years ago in Africa. Science has suggested the African exodus of modern humans started between 60,000 and 70,000 years ago, but much remains a mystery about this dispersal because of the scarcity of human fossils from this time.
This ancient human skull fragment, including the top but not the jaw, may come from a close relative of the first modern humans to colonize Europe. The fossil was discovered accidentally in 2008, when a bulldozer clearing land for a development in Manot near the Sea of Galilee unearthed an opening to a limestone cave. The original entrance to the cave was sealed off by a rock fall about 30,000 years ago, making it a relatively pristine time capsule," says BGU's Dr. Ofer Marder, one of the leaders of the study.
Amateur speleologists were the first to explore the cave, and they spotted the battered bone - the top portion of a skull - resting on a ledge. The Israel Antiquities Authority soon launched a complete survey of Manot Cave, finding buried stone tools at several spots that are still being excavated.
"Here we actually hold a skull of a human being that was living next to the Neanderthals," said Israel Hershkovitz, the leader of a study published recently in Nature. "Potentially he is the one that could interbreed with the Neanderthals," said Hershkovitz, who is a physical anthropologist at Tel Aviv University in Israel.
Genome studies of Neanderthals (Homo neanderthalensis) and of both ancient and contemporary H. sapiens suggest that the two species interbred somewhere in the Middle East between 50,000 and 60,000 years ago, but no remains of anatomically modern humans have been discovered in the Middle East from this crucial period, after H. sapiens left Africa and before it colonized Europe and Asia.
According to Hershkovitz, the skull was unquestionably fromH. sapiens, because it was similar in shape to those of earlier African and later European humans. A patina of calcite coated the fragment, and the researchers used radioactive uranium in the mineral to date the bone to about 55,000 years old. That means that the Manot people are probably the forefathers of the early Palaeolithic populations of Europe, Hershkovitz said.
The Manot people are also a leading candidate for the humans that bred with Neanderthals, giving all of today's non-African humans some Neanderthal heritage. The Manot Cave is near two other sites that held Neanderthal remains of a similar age.
"The southern Levant is the only place where anatomically modern humans and Neanderthals were living side by side for thousands and thousands of years," Hershkovitz said. "The ultimate proof would be to look for the presence of Neanderthal ancestry in DNA from the skull, but the region's balmy temperatures mean that ancient DNA is unlikely to have been preserved."