A huge wooden monument arranged in two circles measuring hundreds of metres across was burned as part of fire rituals, centuries before Stonehenge was built.
The site of the fire monument at Avebury in south-west England was thought to be about the same age as the more famous Neolithic circle at Stonehenge. It was first discovered about 30 years ago. But analysis of the charred remains of this large wooden structure now shows that it is in fact 5,300 years old.
"It's much too large to be a stock enclosure; it's got to be a ceremonial enclosure," study author Alex Bayliss, a statistical archaeologist with Historic England, told Live Science. "It's completely unlike anything we've ever found in the British prehistory."
Bayliss and his team used radiocarbon dating to find the age of the charred wood and fragments of pottery to find a more precise estimate for the site's age. It came out as about 3300 BCE, suggesting the people of prehistoric Britain were burning circular monuments in fire rituals before they started constructing large circles in stone.
The monuments were made up of closely spaced, large pillars made from thousands of nearby oak trees. They were dug into pits in the ground to support their weight. The two circles sat almost side by side, with the largest about 250 metres across.
"It's like a pair of glasses: There's two circles with a small gap in between them," said Bayliss.
The analysis also found that the site was occupied by people long before the fire monument was constructed. Pottery shards and the remains of houses found at the site suggest that there were people living in Avebury many thousands of years ago.
"There's shed loads of stuff happening in the 700 years before and shed loads of stuff after, but there's almost nothing in the middle," Bayliss said.
The wooden monument is found among a cluster of pagan monuments in south-west Britain. The nearest is Avebury henge, the largest prehistoric stone circle in Europe. About 25 miles to the north-east lies the Uffington White Horse, thought to have been a site of sun worship in ancient Britain. Stonehenge itself lies about 23 miles to the south of Avebury.
The findings are reported in the journal British Archaeology.