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Fossils Push Human Emergence Back To 195,000 Years Ago
Salt Lake City UT (SPX) Feb 17, 2005 When the bones of two early humans were found in 1967 near Kibish, Ethiopia, they were thought to be 130,000 years old. A few years ago, researchers found 154,000- to 160,000-year-old human bones at Herto, Ethiopia. Now, a new study of the 1967 fossil site indicates the earliest known members of our species, Homo sapiens, roamed Africa about 195,000 years ago. "It pushes back the beginning of anatomically modern humans," says geologist Frank Brown, a co-author of the study and dean of the University of Utah's College of Mines and Earth Sciences. The journal Nature is publishing the study in its Thursday Feb. 17, 2005, issue. Brown conducted the research with geologist and geochronologist Ian McDougall of Australian National University in Canberra, and anthropologist John Fleagle of New York state's Stony Brook University. The researchers dated mineral crystals in volcanic ash layers above and below layers of river sediments that contain the early human bones. They conclude the fossils are much older than a 104,000-year-old volcanic layer and very close in age to a 196,000-year-old layer, says Brown. "These are the oldest well-dated fossils of modern humans (Homo sapiens) currently known anywhere in the world," the scientists say in a summary of the study. Significance of an Earlier Emergence of Homo sapiens Brown says that pushing the emergence of Homo sapiens from about 160,000 years ago back to about 195,000 years ago "is significant because the cultural aspects of humanity in most cases appear much later in the record � only 50,000 years ago � which would mean 150,000 years of Homo sapiens without cultural stuff, such as evidence of eating fish, of harpoons, anything to do with music (flutes and that sort of thing), needles, even tools. "This stuff all comes in very late, except for stone knife blades, which appeared between 50,000 and 200,000 years ago, depending on whom you believe." Fleagle adds: "There is a huge debate in the archeological literature regarding the first appearance of modern aspects of behavior such as bone carving for religious reasons, or tools (harpoons and things), ornamentation (bead jewelry and such), drawn images, arrowheads. "They only appear as a coherent package about 50,000 years ago, and the first modern humans that left Africa between 50,000 and 40,000 years ago seem to have had the full set. As modern human anatomy is documented at earlier and earlier sites, it becomes evident that there was a great time gap between the appearance of the modern skeleton and 'modern behavior.'" The study moves the date of human skulls found in Ethiopia's Kibish rock formation in 1967 back from 130,000 years to a newly determined date of 195,000 years ago, give or take 5,000 years. Fossils from an individual known as Omo I look like bones of modern humans, but other bones are from a more primitive cousin named Omo II. In addition to the cultural question, the earlier date for humanity's emergence is important for other reasons. "First, it makes the dates in the fossil record almost exactly concordant with the dates suggested by genetic studies for the origin of our species," Fleagle says. "Second, it places the first appearance of modern Homo sapiens in Africa many more thousands of years before our species appears on any other continent. It lengthens that gap. � Finally, the similar dating of the two skulls indicates that when modern humans first appeared there were other contemporary populations [Omo II] that were less modern." The study was funded by the National Science Foundation, the L. S. B. Leakey Foundation, the National Geographic Society and the Australian National University. Modern Homo in the Valley of the Omo Richard Leakey and his team of paleontologists traveled in 1967 to the Kibish Formation along the Omo River in southernmost Ethiopia, near the town of Kibish. They found the skull (minus the face) and partial skeleton (parts of arms, legs, feet and the pelvis) of Omo I, and the top and back of the skull of Omo II. Brown was not part of the 1967 expedition, but was working nearby and got to look at the site and the fossils. "Anthropologists said they looked very different in their evolutionary status," Brown recalls. "Omo I appeared to be essentially modern Homo sapiens, and Omo II appeared to be more primitive." In 1967, the fossils were dated as being 130,000 years old, although the scientists doubted the accuracy of their dating technique, which was based on the decay of uranium-238 to thorium-238 in oyster shells from a rock layer near the skulls. Fleagle says no scientist has been bold enough to suggest Omo II is anything other than Homo sapiens, and that "quite often at the time of major events in evolution, one finds an increase in morphological [anatomical] diversity." Now that the new study confirms Omo I and Omo II are the same age � living within a few hundred years of each other about 195,000 years ago � some anthropologist suggest "maybe it [Omo II] isn't so primitive after all," Brown says. McDougall, Brown and Fleagle and researchers from other universities returned to Kibish in 1999, 2001, 2002 and 2003. They identified sites where Omo I and Omo II were found in 1967, and obtained more of Omo I, including part of the femur (upper leg bone) that fit a piece found in 1967. They also found animal fossils and stone tools, and studied local geology. The Nature study includes initial results from those expeditions.
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