Scientists discover the oldest human fossils outside Africa
January 25 at 2:00 PM
An ancient jawbone uncovered from a collapsed cave on the coast of Israel is at least 175,000 years old, and it belonged to a member of our own species. Sophisticated stone tools were discovered nearby.
The find, reported Thursday in the journal Science, is by far the oldest human fossil ever uncovered outside Africa, where our Homo sapiens originated. It pushes back the timeline of when modern humans began venturing to other continents by about 60,000 years and suggests people made several short-lived excursions into Eurasia millennia before we finally conquered the globe.
The owner of this jawbone was probably one of those early unsuccessful explorers â" a tangent in the story of humanity, said Rick Potts, director of the Human Origins Program at Smithsonian's National Museum of Natural History. That does not mean it has nothing to tell us. Potts, who was not involved in the discovery, compared the Israeli fossil with the remains of failed colonization attempts like the Viking settlements in Newfoundland.
âIt's inherently fascinating and interesting,â he said. âNot only throughout history but deep into our prehistory, there have been these pioneers .â.â. that were not able to survive.â
The jawbone, with eight teeth still embedded inside it, was excavated from Misliya Cave on the western slopes of Israel's Mount Carmel. Today the site is little more than a jumble of rubble shadowed by a rock overhang. Yet from about 250,000 to 150,000 years ago, before it collapsed, the cavern was vast and deep. From this high perch above the sea, the resources of the Mediterranean, the coastal plain and the forested mountain range were within easy reach. According to University of Haifa archaeologist Mina Weinstein-Evron, a co-author of the Science study, this was a perfect shelter for ancient ho minins â" the group that includes humans and our extinct relatives.
A view from below of Misliya Cave, on the western slopes of Mount Carmel in Israel. (Mina Weinstein-Evron/Haifa University)
Weinstein-Evron has worked at the Misliya site for nearly two decades, uncovering scores of discarded tools, animal bones, even evidence of fire â" discoveries that span the 100,000 years in which the cave was in use. The jawbone is the only remnant of any hominin species found so far.
âIt was very exciting,â she recalled. âA full jaw with all the teeth .â.â. is not something you find very often.â
A single jawbone cannot reveal everything about an individual â" for example, Weinstein-Evron does not know if this fossil belonged to a man or a woman â" but it can tell a lot. Af ter all, you are what you eat; much information about a species is encoded in its mouth.
At first glance, this bone looked like it came from the mouth of a modern human. The fossil lacked the pronounced shovel-shaped canines of a Neanderthal, and it had the straight-edged incisors characteristic of our species. The shape of its jaw also resembled our own.
Weinstein-Evron and her colleagues were meticulous. They spent more than a decade analyzing the remains and sought to determine their age using three distinct dating methods. Collectively, the results indicate the fossil is somewhere between 177,000 and 194,000 years old.
The jawbone's owner may have been ancient, but he or she was no rube. Uncovered alongside the fossil were stone points made using an advanced form of stone knapping called the Levallois technique. This method of tool production involved carefully cutting a stone around the outline of a desired shape, so that when the final blow is struck, a perfect point emerges.
âIt's very sophisticated, because it shows abstract thinking,â Weinstein-Evron said. âYou have to plan ahead what you want to get from a certain core.â
The stone points and a 3-D reconstruction of the jawbone recovered at Misliya Cave are superimposed over a map of early modern human fossil sites in Africa and the Middle East. The fossils from Jebel Irhoud, in Morocco, date to at least 300,000 years ago. Those at Omo Kibish and Herto are similar in age to Misliya. (Rolf Quam/Binghamton University; NASA)
Shara Bailey, an anthropologist at New York University who specializes in fossil teeth, said she found the conclusions about the identity and the age of the jawbone convincing â" and not too shocking. The history of humanity has grown increasingly complex in recent years.
Traditionally, scientists pegged Homo sapiens' migration out of Africa to some time between 75,000 and 60,000 years ago. That date is inscribed in DNA: genetic analyses of people from Europe, Asia, Australia and the Americas suggest they all descend from explorers who left Africa during this period.
Excavations in China have uncovered fragmentary evidence of hanky-panky between Neanderthals and modern humans as early as 113,000 years ago. DNA analysis of remains from mysterious people known as the Denisovans suggests an ancient world that looked like Tolkienâs Middle Earth â" except instead of hobbits, elves and dwarves wandering around, our planet had many species of interacting, interbreeding hominins.
Bailey herself was part of a team of researchers who last year reported the discovery of Homo sapiens fossils in Morocco that were at least 300,000 years old.
With so much evidence to push back the timel ine of humans' evolution and exploration, Bailey said, âitâs not that surprising that weâre going to start seeing them outside of Africaâ at an early stage.
âOf course,â she added, âthey haven't gone very far.â
They also probably did not last very long; modern humans' DNA bears no genetic signal of such an early migration, Potts noted.
Despite that â" or really, because of it â" the jawbone raises many more questions than it answers, said Israel Hershkovitz, an anthropologist at Tel Aviv University and the lead author of the study.
For example, the age of the jawbone implies that Homo sapiens overlapped with Neanderthals and other hominin species during our ventures (or misadventures) in western Asia. So what happened? Did interbreeding during this time period lead to the later fossils found in China? It is possible, he said.
Hershkovitz also wants to investigate why those early explorers traveled to Israel â" was the journey made possible by changes in climate? â" and whether traits acquired in the region influenced later human evolution.
Meanwhile, Potts posed the question that is asked about all vanished societies: What went wrong?
âWhy didn't they begin the process of worldwide colonization?â he wondered. âWere they perhaps too isolated from other groups? Were they not able to withstand environmental changes that challenged their survival?â
The answers will not just explain the demise of the jawbone's owner, Potts said. It may also help us understand the success of those who followed in his or her footsteps 100,000 years later.
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Oldest Homo sapiens fossils discovered in MoroccoSource: Google News US Science | Netizen 24 United States