The study, to be published Friday in the journal Science, adds to a growing body of evidence that primitive humans were more intelligent, organized and resourceful than previously believed. Other scientists reported this week the discovery in Germany of some 400,000-year-old spears and evidence of a skilled hunting culture.
Waters said these findings are a surprise because most researchers had thought sophisticated survival skills came into wide use among ancient humanlike animals only with the appearance about 150,000 years ago of anatomically modern humans.
The Siberian site studied by Waters and his team is called Diring Yuriakh. It is located on a plateau above the Lena River, near the town of Yakutsk about 480 km south of the Arctic Circle.
Russian archaeologists first excavated the site in 1982 and discovered that it was an ancient quarry that had been used during several different periods of human occupation over many thousands of years.
Waters and colleagues from the University of Illinois were invited to determine the age of the oldest site using a technique that counts the number of electrons trapped in the grains of quartzite sand.
The Americans took a number of samples, said Waters, and determined that the crude stone tools were between sediment layers 260,000 to 370,000 years old.
Waters said the weather in Siberia 300,000 years ago is thought to have been very much like the present-day weather. Winter temperatures at Diring Yuriakh routinely drop to minus 50, and the soil freezes down to about 1 meter.
No bones, animal or human, have been found in Diring Yuriakh, and Waters said it is uncertain how long the ancient humans lived there. Their primary food source also is unknown, he said, although the nearby Lena River probably had fish, and large animals, such as elephant-like mammoths, lived in the area.
"We know very little about these humans," said Waters. He said it is not known which of the premodern human species could have lived at the Siberian site 300,000 years ago.
Some scientists have said the crude stone tools found at Diring Yuriakh were actually made by natural processes, not by human hand. But archaeologist Rob Bonnichsen of Oregon State University said he believes the site analyzed by the Waters team clearly was once a home to an ancient people.
"It is obvious that this is a human site," said Bonnichsen.
The fist-size stone tools recovered from the site are thought to be quartz stones that were shaped by pounding them against other stones until a sharp edge was developed. The process left markings that could not be made by natural forces, said Waters.
But the ultimate proof came when scientists found a debris pile at what may have been a toolmaker's work station. In the debris pile were distinctive quartz flakes. Some of the flakes could be fitted exactly into the sharpened faces of some of the stone tools, said Waters.