These remains were dated to the monument's first phase, when a circular bank and ditch were created on Salisbury Plain.
The second cremation, from inside the ditch surrounding Stonehenge, is said to be that of an adult buried between 2930 to 2870 B.C.
The latest burial studied, from the ditch's northern side, was identified as that of a woman in her twenties. It dates to 2570 to 2340 B.C.—the period when the huge sandstone blocks known as sarsen stones were put up.
"We're looking at a long-term use of the monument for burying the dead," Parker Pearson said.
It's estimated that up to 240 people are buried at Stonehenge in total, mainly in the Aubrey Holes. It is the largest known cemetery of its time in Britain.
The remains of almost 50 ancient people were dug up in the 1920s, but they were thought to be of no scientific value and so were reburied.
Previous excavations by the project team indicate that Stonehenge was linked via the River Avon and two avenues to a matching timber monument at nearby Durrington Walls.
The paired circles—Stonehenge and the wooden circle at Durrington—represented the realms of the living and the dead, according to Parker Pearson.
The theory is that the majority of the dead were deposited in the river upstream at Durrington Walls. Only "a select few"— possibly because of their special status as members of an elite dynasty of rulers—were buried at Stonehenge itself, he said.
The new dating evidence indicates that these chosen few must have been interred over centuries.
Artifacts buried with these dead are sparse, but one of them provides a clue. "One of the grave goods from Stonehenge is very unusual. It's the head of a stone mace, and it's the kind of artifact that may well have been a symbol of authority," he said.
Parker Pearson notes that a later burial from around 2000 B.C. at a nearby site called Bush Barrow belonged to an important chief, who possessed a similar mace.
The team uncovered a small section of the River Avon's ancient streambed in hopes of finding the remains of common folk whose bodies had been ceremonially thrown in.
Burnt hazel sticks were found, but no bones.
"It's a shame, but the odds were kind of against us," said Parker Pearson, who wasn't permitted to excavate where he suspects the dead were put in the river, at the point where the Avon meets the avenue leading down from Durrington Walls.
Andrew Fitzpatrick of Wessex Archaeology, a consulting firm based in Salisbury, wasn't part of the study team.
He said the new dates for the cremation burials are consistent with other evidence.
But on their own, three dates don't prove Stonehenge was used continually as a cemetery, he said.
"And of course, the team is dealing with material from old excavations, so they can't be 100 percent confident where it comes from," Fitzpatrick said.
Archaeologists working at Stonehenge are in a "very difficult position" because of the destruction caused by past digs and the desire to preserve what's left, he commented.
The idea that the Stonehenge burials represent a prehistoric elite fits in with a pattern seen elsewhere, Fitzpatrick said.
"At no stage in prehistory in Britain do we seem to have enough burials," he said.
"So the extension to that argument is that only certain people are being chosen for burial.
"The rest are either left out in the wild for scavenging animals to pick their bones clean. Or they're just thrown into rivers."
Seasonal Village Found
The Stonehenge Riverside Project's other finds in 2007 included further insights into a large seasonal village at Durrington Walls, where the builders of Stonehenge likely lived.
One of the houses was found to have been made of chalk plaster—the earliest such construction known in Britain.
"All the little details of daily life were preserved in the floor," such as the imprints of beds, a dresser, and an oval-shaped hearth, the Riverside project's Parker Pearson said.
Several houses were also uncovered along the avenue to the river, which may have been used by spectators during religious processions, he said.
Other team members found evidence that some of the stones at Stonehenge were transported earlier than believed and had a previously unsuspected source.
A megalith referred to as the Altar Stone has been thought to have been picked up in Milford Haven, Wales—the assumed departure point for the monuments' "bluestones," from the Preseli Hills in southwest Wales, which are thought to have been floated across the sea to England.
But a new geological study of the Altar Stone suggests it actually came from the Brecon Beacons region of inland Wales, in which case it would have been lugged overland to England.
"There may well have been a much wider series of sources for these stones," Parker Pearson said.
Furthermore, fragments of the same type of Welsh stone were identified from the nearby Stonehenge Cursus—a long, cigar-shaped ditched enclosure. The Cursus had been created centuries before the stone circle was constructed.
"It's making us think that this connection with Wales might really have been quite long lasting and not just to do with Stonehenge," Parker Pearson said.
SOURCES AND RELATED WEB SITES