Archaeologists have long thought that the first campfire was lighted by Homo erectus some 500,000 years ago, in a cave near Zhoukoudian, China. But a reanalysis of the cave, reported in tomorrow's Science , has turned up no hearths, no ashes, and none of the unique chemical signatures expected from fires. That means Homo erectus may have spread through Asia and into cold northern latitudes starting about 1.8 million years ago without fire.
The Zhoukoudian site was first excavated in the 1920s and '30s, when researchers found hominid fossils, stone tools, burnt bones, and what they described as ancient hearths preserved as layers of ash up to several meters thick. It all seemed to add up to solid evidence of human control of fire; some researchers even concluded that the thick ash layers represented continuous occupation over thousands of years.
In 1996 and 1997, a team led by structural biologist Steve Weiner of the Weizmann Institute for Science in Rehovot, Israel, revisited the site, a sheer cliff cut into a hillside. Perching on a 10-story-high scaffolding, the researchers focused on layers 10 and 4, previously noted for putative king-sized hearths. In the lab, they confirmed that a small number of bones had been burned. But the sediments contained no ash or siliceous aggregates, soil-derived minerals that are cemented together in trees and stay intact after burning--and should be present at the site of almost any wood fire. The thick layers aren't ash at all, but accumulations of organic material, much of it laid down under water, says Weiner.
The paper also raises questions about whether humans actually lived at the site, because the researchers describe it not as a traditional cave but as an enlargement of a vertical fault, open to the sky. "This is an important reinterpretation," says anthropologist Rick Potts at the National Museum of Natural History in Washington, D.C. "It means that, who knows, maybe it wasn't a home."