for National Geographic News
Human fossils found 38 years ago in Africa are 65,000 years older than previously thought, a new study sayspushing the dawn of "modern" humans back 35,000 years.
New dating techniques indicate that the fossils are 195,000 years old. The two skulls and some bones were first uncovered on opposite sides of Ethiopia's Omo River in 1967 by a team led by Richard Leakey. The fossils, dubbed Omo I and Omo II, were dated at the time as being about 130,000 years old. But even then the researchers themselves questioned the accuracy of the dating technique.
The new findings, published in the February 17 issue of the journal Nature, establish Omo I and II as the oldest known fossils of modern humans. The prior record holders were fossils from Herto, Ethiopia, which dated the emergence of modern humans in Africa to about 160,000 years ago.
"The new dating confirms the place of the Omo fossils as landmark finds in unraveling our origins," said Chris Stringer, director of the Human Origins Group at the Natural History Museum in London.
The 195,000-year-old date coincides with findings from genetic studies on modern human populations. Such studies can be extrapolated to determine when the earliest modern humans lived.
The findings also add credibility to the widely accepted "Out of Africa" theory of human origins which holds that modern humans (later versions of Homo sapiens) first appeared in Africa and then spread out to colonize the rest of the world.
The new date also widens the gap between when anatomically modern humans emerged and when "cultural" traitssuch as the creation of art and music, religious practices, and sophisticated tool-making techniquesseem to have appeared. Evidence of culture is not extensively documented in the archaeological record until around 50,000 years ago.
The wider gap could add fuel to a long-term debate swirling around when modern human behavior, as opposed to modern human anatomy, emerged.
"Those who believe that there is widely scattered evidence of 'modern' behavior going back 200,000 years in Africa will be delighted that modern human anatomy also goes back that far," said John Fleagle, a physical anthropologist at Stony Brook University in New York and one of the co-authors of the study. "[Scientists] who believe that modern human behavior only appeared abruptly about 50,000 years ago will see [the new date as] further expanding the distinction and the temporal gap between modern anatomy and modern behavior."
Dating Through Geology
Somewhat surprisingly, the first thing the scientific team had to do to come up with the new dates was to relocate the precise location where the fossil remains had been excavated in 1967. They were able to do this using National Geographic Society video footage taken during the first excavation. They also used photographs taken by Karl Butzer, a geologist currently at the University of Texas, who did the original geological studies of the site. Also helpful were hand-drawn maps from the late Paul Abell, another member of the 1967 team.
"So we know where Omo I and Omo II are now, and they're now documented by GPS, so they won't get lost again. But we didn't have GPS 40 years ago," said Frank Brown, a geologist at the University of Utah and a co-author of the study.
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