The researchers came to that conclusion after radiocarbon dating of human remains found at the site indicated people had been buried there between about 3000 and 2500 B.C.
Stonehenge, near Salisbury, England, is a prehistoric monument of giant stones -- some as heavy as 50 tons and as tall as 16 feet -- arranged in a circular setting and surrounded by an earthen bank and ditch. The stones are oriented toward the rising sun during the summer solstice.
The oldest parts of the site -- the bank and ditch -- date to about 3100 B.C., and the last large stones were erected around 2500 B.C.
For years, Archaeologists have debated the purpose of the monument, suggesting that it might have been an astronomical observatory, a cemetery, or a religious complex.
But until recently, researchers thought that people were only buried at the site for about 100 years, from about 2700 to 2600 B.C.
The new research, though, suggests that the site was used for burying cremated remains for at least 500 years.
"It's now clear that burials were a major component of Stonehenge in all its main stages," archeologist Mike Parker Pearson, of the University of Sheffield in England, told the New York Times.
Parker Pearson and his colleagues studied the remains of three people, all of which were excavated in the 1950s and had been stored at the nearby Salisbury Museum. It's only in the past few years that radiocarbon dating methods have advanced enough to determine the remains' age, Parker Pearson said -- in the 1920s, for example, researchers dug up 49 other cremation remains, but reburied them after they decided that the remains couldn't be scientifically useful.
Parker Pearson and his colleagues found that the earliest remains date from between about 3030-2870 B.C., around the time the first earthen banks were being built. The next remains date from between about 2930-2870 B.C., and the youngest date from between 2570-2340 B.C., when the last stones were being erected.
The same research team in 2006 found the evidence of a seasonally occupied village two miles from the monument. They suggested that the village, which held more than 300 houses, was part of the same ceremonial complex as Stonehenge, connected by the River Avon.
"What we suspect is that the river is the conduit between the two realms, of the living and the dead," Parker Pearson told Reuters. "It was the prehistoric version of the River Styx."
Not everyone, however, was buried at Stonehenge. In fact, the researchers suspect that the site was the burial ground for one royal family over many generations. That's because there are relatively few remains there -- about 240, the researchers estimate -- and because they increase in the later years of the site, as the descendents of one family would multiply over time.
Some researchers are still skeptical of parts the new theory. Mike Pitts, editor of the journal British Archaeology, told National Geographic magazine that researchers must still figure out, for example, why some of the surrounding area was used for farming and grazing if it was such an important ceremonial site.
Still, he told the magazine, "The value of this interpretation is [...] that it works with the entire landscape. Previous interpretations have taken the independent sites separately."
The research is part of the ongoing Stonehenge Riverside Project, a seven-year investigation of the Stonehenge area supported by the National Geographic Society, which will run through 2010.
Photo by Ken Geiger/National Geographic Society
