One of the biggest mysteries surrounding the site of Stonehenge is precisely how they were made.
The stone circle monument, built by Neolithic people, is largely made from two types of stone. There are the smaller slabs known as bluestones, which are known to have come from the Preseli Hills in southwest Wales. The larger standing stones, known as megaliths, are made of sarsen, a local sandstone.
Archaeologists and historians have been baffled by where precisely the sarsen. Given the technological limitations of the people who constructed the monuments, there has been some speculation how the stones got there in the first place.
Well, now it looks like they have an answer.
Experts suspected for a long time that the stones could have originated from the Marlborough Downs, a group of hills north of the monument -- but the truth had been "impossible to identify until now," said the statement from English Heritage, which looks after the site. The final clue came when a piece of Stonehenge was returned to the site by a former excavation employee, who removed it in 1958.
"When Robert (the employee) decided to return the core last year, experts started piecing together a puzzle," tweeted English Heritage. The team, funded by the British Academy, tested on the sarsen stones and the missing piece, which showed that most shared a similar chemistry and came from the same area. They then sampled all the sarsen in the country for a match.
They found a match in West Woods, about a 40-minutes' drive away. It's a beautiful forest favored by hikers and cyclists, and it appears to be the source of Stonehenge's stone.
"It has been really exciting to harness 21st century science to understand the Neolithic past, and finally answer a question that archaeologists have been debating for centuries," said David Nash of the University of Brighton, who led the study.
"We can now say, when sourcing the sarsens, the over-riding objective was size -- they wanted the biggest, most substantial stones they could find and it made sense to get them from as nearby as possible," said historian Susan Greaney, one of the study's co-authors, in the English Heritage statement. "This is in stark contrast to the source of the bluestones, where something quite different -- a sacred connection to these mountains perhaps -- was at play."
"Yet again this evidence highlights just how carefully considered and deliberate the building of this phase of Stonehenge was," she added.
"Our results further help to constrain the most likely route along which the sarsens were transported to Stonehenge," said the study. For instance, researchers can now rule out previous theories that the stones traveled from the village Avebury south or southwest to Stonehenge.
"To be able to pinpoint the area that Stonehenge's builders used to source their materials around 2500 BC is a real thrill," said Greaney in the statement. "Now we can start to understand the route they might have traveled and add another piece to the puzzle."