"Any uncertainty to the result would come from the assumption of a constant rate of sedimentation during the reverse polarity period, yet this uncertainty is likely to be small," said Hoffman.
Evidence of Adaptability
The researchers do not know exactly how the early tools were used. They consist of several kinds of scrapers and sharp-edged tools, which almost certainly would have been used to cut meat off the bones of mammals that inhabited the region.
"That far north, we are dealing with changes in daylight," said Richard Potts, director of the Human Origins Program at the Smithsonian Institution's National Museum of Natural History in Washington, D.C., and co-author of the scientific paper. "There would have been a good growing season and a season of relative dearth. Reliance on animal food during certain parts of the year may have been pretty important."
As corroborating evidence that early humans were able to thrive in varied climatic conditions over a million years ago, the researchers point to Lantian, an archaeological site on the Yellow River about 560 miles (900 kilometers) southwest of the Nihewan Basin. It was there that the remains of a 1.1 million year old Homo erectus were excavated in 1963.
Paleoclimatic evidence suggests that Lantian was a relatively cold and windy place 1.1 million years ago, said Potts.
"These two localities suggest that populations were able to occupy or shift their range over a considerable area, from Nihewan to the southern margin of the Loess Plateau, during a time of enhanced global and regional climatic variability that included intermittent aridification of north China," the researchers conclude in Nature.
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