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Cal scientist resolves debate on Neandertals' age
Updated 8:01 am, Friday, June 20, 2014
A Berkeley scientist who uses powerful instruments to determine the ages of everything from the Earth's crust to Polynesian temples has used the technology to define just when nearly half a million years ago the earliest Neandertal people lived and died.
By determining that those ancient people were living "most probably" about 434,000 years ago, Warren D. Sharp, a geologist at the Berkeley Geochronology Center, has resolved a long-simmering uncertainty over the ages of the fossils, which are providing scientists with new insights into human evolution.
The fossils, including thousands of tiny fragments, scores of complete bones, and at least 17 remarkably complete skulls, were discovered nearly 25 years ago in Northern Spain's Atapuerco mountains. They were found inside a cave, huddled together in what is now known as the Sima de los Huesos - the "Pit of the Bones."
The area is now a United Nations "World Heritage Site," protected because the remains are valuable to science and because they are the largest collection of Neandertal fossils ever discovered anywhere.
Whether those Neandertal people were members of a clan and whether the pit was a ritual burial place are mysteries that remain unsolved, said Juan-Luis Arsuaga of Madrid's Complutense University, who is an anthropologist and leader of the international team analyzing the fossils.
Arsuaga's team of 30 scientists, including Sharp and James L. Bischoff of the U.S. Geological Survey in Menlo Park, reported new details of the Neandertal discovery and their ages in the journal Science on Thursday.
Dating the fossils is a key to understanding how those ancient people evolved in Europe, long before modern humans arrived to spread across the continent - and finally end the Neandertal presence some 35,000 years ago.
Some scientists have dated them to as long as 850,000 years ago - "too old to be credible," Sharp said - and some put them as recently as 200,000 to 320,000 years old.
Sharp is an expert on dating ancient material - from recent centuries-old Hawaiian artifacts recently found by archaeologists to geological formations in the Earth's crust many millions of years old.
Three years ago, he and Bischoff traveled to the Pit of Bones in Spain and gathered samples of the limestone that had formed on the fossil skulls over the millennia. They brought the samples back to Berkeley's Geochronology Center, which is noted for its advanced age-dating instruments.
Sharp focused the center's tools on the limestone that covered one of the fossil skulls, on quartz grains in surrounding nearby sediments, and on fossil teeth from the skulls.
Using the Center's advanced mass spectrometer, Sharp measured his tiny samples in parts per billion and vaporized them at nearly 14,000 degrees Fahrenheit to determine the rate at which the radioactive element uranium in the limestone had decayed into the stable element thorium. It was similar in principle to the radiocarbon dating systems familiar to countless college students.
His final age estimate for the fossils in the Pit of Bones, Sharp concluded, was between 410,000 and 470,000 years ago and "most probably" 434,000 years ago - a date that will now be established for the Neandertal people who died in the "Pit of Bones."
During a telephone news conference from Madrid on Thursday, Arsuaga likened his story of the fossils to a scenario from "The Game of Thrones."
The curious shape of the teeth and lower jaws of one skull, he said, indicated that as the Arctic cold of a long-ago ice age came upon these early Europeans, "the people had no choice between moving south or going extinct." They obviously survived - for a time.