How did prehistoric Britons manage to move Stonehenge's stones? Each rock weighed an average of 25 tons and stood as tall as 30 feet, and the first tractor was still five millennia away, so clearly they must have endured great pains to build the monument, right?
Much of the mystery around the site comes from the questions of how Stonehenge was built and why. A recent experiment by archaeologists at University College London provides a hint to that first part anyway.
As back-breaking a task as building a monument of dump truck-sized stones without the aid of modern machinery might seem, the demonstration held in London's Gordon Square suggests it wasn't that difficult at all.
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Last week, University College London doctoral candidate Barney Harris put out a call for volunteers to see how many people it would take to pull a stone about half the size as the smallest rock at Stonehenge, which is about one metric ton. Harris anticipated it would take a team of at least 15 people to move the stone, and as many as 40 to 50 to lift it.
Instead, 10 people were able to get the stone going at a rate of roughly 10 feet (3 meters) every five seconds, or around one mile (1.6 kilometers) per hour. A team twice the size would be able to move a small piece of Stonehenge.
Devoting the kind of human capital needed for what may appear to be a frivolous effort for a Neolithic society isn't all that far-fetched considering settlements in the area at the time numbered in the thousands, so there were plenty of other members of the society to carry on with the more life-sustaining activities, such as farming, hunting or child-rearing.
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Made of rope, a wooden track and a sycamore sled, the design of the rig used in the experiment mirrors others found throughout the ancient world. "We know that pre-industrialized societies like the Maram Naga in India still use this kind of sledge to construct huge stone monuments," Harris told The Telegraph. "And similar y-shaped sleighs have been found dating back to 2000 B.C. in Japan which we know were used to move megaliths."
Recreating even at a small scale how the rocks used at Stonehenge were transported can provide researchers an estimate of how long it took to complete the entire site.
Beginning around 5,000 years ago, the first stones were lain at Stonehenge. The monument was built in two phases with two different kinds of stones. The largest stones are called sarsens, a local sandstone, placed around 2400 B.C. The circle of rocks at the center, known as bluestones, were erected 500 years earlier, around 2900 B.C.
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Neolithic people quarried the slabs of bluestone in Preseli hills in Pembrokeshire, Wales. The builders then transported the rocks 140 miles (225 kilometers), through steep and uneven terrain, to the site of the monument in Wiltshire, England, reported a separate University College London study last year. The system devised in the most recent experiment works well over these rough patches and without the aid of livestock.
Knowing how ancient builders could have constructed Stonehenge does take a little mystery out of the site. But if nothing else, Stonehenge still stands as a marvel of ancient ingenuity, erected by people smart enough to make the effort as easy on themselves as possible at the time.