Oct. 28, 1998 TORONTO---Some 780,000 years ago, the first Europeans were using simple stone tools to scratch out a living in a cave called Gran Dolina in the Atapuerca Mountains of northern Spain. Whether they were direct ancestors of modern Homo sapiens or an evolutionary dead end like the Neanderthals is for anthropologists to decide. But Josep Pares is certain of one thing: they were living there 780,000 years ago.
An expert on paleomagnetic dating, Pares, who is now a University of Michigan research scientist, first reported the age of the Atapuerca hominid fossils in an article published in Science on Aug. 11, 1995, with colleague Alfredo Perez-Gonzalez. Since no hominid fossils or tools older than 500,000 years had ever been discovered in Europe before, Pares' date was highly controversial.
Pares based his date for the Gran Dolina fossils on the orientation of magnetic minerals in the rock layer in which the fossils were found. In the early 1900s, scientists discovered that magnetic minerals in rocks work like tiny compass needles---pointing toward the location of the Earth's magnetic field at the time the rock was created.
Today Earth's magnetic field lies to the north, but it wasn't always that way. The field has switched back and forth between north and south many times in the Earth's 4.5-billion-year history. The last major switch from south to north, which scientists call the Matuyama/Brunhes reversal, took place about 780,000 years ago. This reversal marks the boundary between the lower and middle Pleistocene geological epochs.
"Because the Gran Dolina fossils were found below the Matuyama/Brunhes boundary with a clear signal of reversed polarity, we are confident the date is accurate," Pares said.
At the Geological Society of America meeting here today (Oct. 27), Pares discussed the reliability of paleomagnetic dating and explained the contributions it has made to increased understanding of early hominid evolution in Africa and Asia.
Pares also presented new information on hominid fossils and stone tools excavated from Elefante and Galeria---two other Atapuerca sites near Gran Dolina.
"Stone tools have been found at Elefante, but we have been unable to date them, because we still have not found the polarity reversal for the Matuyama/Brunhes boundary. We did locate the boundary at Galeria, but all fossils and tools found there so far were above the boundary and more recent."
Pares added that he has just begun work at the Guadix-Baza Basin in southern Spain---another site where hominid fossils have been found. Some anthropologists claim these fossils could be as old as 1.8 million years. "So far the paleomagnetic data from Guadix-Baza is ambiguous," Pares said. "Hopefully, additional work at the site will give more definitive data and help resolve the controversy."
Research at Atapuerca is funded by the government of Spain. Perez-Gonzalez is currently affiliated with the Universidad Complutense de Madrid in Madrid, Spain.
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