How did prehistoric humans transport and arrange the giant boulders at Stonehenge?

The massive stones on England’s Salisbury Plain have stood for over 4,000 years, witness to the wanderings of prehistoric nomads, to the rise and fall of tribes, to rites, mysteries, and ceremonies forever eclipsed.

Well before the complexity of its design was revealed, the elegance and imposing size of Stonehenge inspired scores of theories about its ancient origins and purpose. Was it a defensive structure? A cemetery? A druidic temple of the moon? A ring of Irish petrified giants, magically carried from abroad, as one imaginative legend suggests?

As early as 1740 Dr. William Stukeley detected the alignment of the main axis with the midsummer sunrise. Since the late 19th century, an increasing number of astronomical links have been established whose sophistication and precision contradict the widespread notion of a prehistoric race more apelike than human.

Astronomer Gerald S. Hawkins, a Stonehenge authority and author of several books on the subject, perceived in the arrangement of stones an elaborate scheme of moon and sun alignments: “Stonehenge I (the earliest construction) had 11 key positions,” he wrote in Stonehenge Decoded, “every one of which paired with another, often more than one other, to point 16 times to ten of the twelve extremes of the sun or moon; Stonehenge III (built later) with its five trilithons and heel stone axis pointed 8 times to eight of those same extremes.” Hawkins further suggested that the monument, so subtle in form, so ingenious in function, acted as a computer to predict the terrifying natural phenomena of solar and lunar eclipses.

The why of Stonehenge may never be unveiled, but archaeological discovery of tools, examination of materials, and meticulous study by authorities Richard J. C. Atkinson and Gerald Hawkins provide more tangible evidence of the how. The enormous task of erecting Stonehenge was carried out by different prehistoric peoples in three major construction stages, ranging over a period of at least 500 years.

The period of first building, Stonehenge I, began around 2200 B.C., as established by radiocarbon dating techniques. At this time, Late Stone Age (Secondary Neolithic) people, probably hunters and farmers from the Continent, built a nearly perfect circular bank 380 feet in diameter. Within it they dug, with pickaxes of red deer antler and shovels of oxen shoulder blades, a roughly circular ditch, originally a series of separate pits 10 to 20 feet wide and 4 1/2 to 7 feet deep, now thought to be quarries. Inside the ditch they piled an impressive circular bank of hard white chalk, 6 feet high, 20 feet wide. The two banks and ditch were left open to the northeast and a huge 35-ton “heel stone” was placed on the entranceway 100 feet outside the enclosure. The dramatic appearance of the midsummer sun over this stone must have inspired celebration and enhanced the power of the priests. To this day it excites visiting crowds.

John Aubrey in the 17th century was the first to spot a sequence of holes within the enclosure, two to four feet deep, deliberately refilled with chalk rubble, bone pins, and cremated human bones. These 56 Aubrey holes, whose purpose is yet unclear, were meticulously placed along a circle 288 feet in diameter. At four of the holes there rose enormous “station stones,” two of which remain. The longer sides of the rectangle suggested by these stones were precisely perpendicular to the summer sunrise line, and the diagonals intersected at the center of the circle.

In approximately 1700 B.C., the Beaker people added to the extraordinary work of their predecessors. Within the enclosure they erected at least 82 bluestones (made of an igneous rock with a bluish tint), weighing up to five tons each, in two concentric circles, the stones of the inner circle perfectly aligned with those of the outer. At this time, too, a majestic 40-foot-wide avenue was formed northeast from the monument and eventually branching eastward to the Avon River 2 miles away.

Approximately 1,000 years later, the powerful, rich, and sophisticated people of Wessex took down the double circle of blue-stones and replaced them with a different pattern of far more massive sarsen boulders of natural sandstone.

At the center they erected a horseshoe of five trilithons (from the Greek words meaning three stones), each comprising two uprights and a lintel, or crosspiece. Here stand the largest of the stones brought to the monument; one sarsen upright measures 29 feet, 8 inches, and weighs 50 tons—the biggest prehistoric stone fashioned by hand in England, according to Hawkins. Around the horseshoe, the Wessex people built a ring of 30 sarsen uprights with connecting lintels, again left open to the northeast.

The 25-ton uprights were uniformly placed, says Hawkins, with “an average error of less than 4 inches.” The tops of the uprights were scooped out to hold the seven-ton lintels, which were further secured by a mortise and tenon system: a knob nine inches high was carved on the top of each upright to fit snugly into a hole dug on the bottom of the lintel, one hole near each end—a staggering feat when one considers the precision of measurement and placement of the stones, and the skillful carving achieved with the roughest stone tools. A pale green boulder of micaceous sandstone, 16 feet long and 31/2 feet wide, was placed before the central trilithon. This has been named, somewhat misleadingly, the altar stone; neither its original position nor its purpose is yet fully explained.

Somewhat later, the people erected a bluestone horseshoe of 19 uprights within the sarsen horseshoe, and a rough circle of bluestones (numbering 59 to 61 according to Atkinson) between the sarsen horseshoe and the sarsen circle. These may originally have been intended for the corresponding number of holes (called Y and Z holes) lying well outside the enclosure, in which pottery shards, chips of bluestone, and fine soil have been found. Finally, all activity at Stonehenge stopped, and the site was probably abandoned around 1400 B.C.

The story of how they got the stones in place must start (now that one has some notion of the meaning of “in place”) with how they got the stones to begin with. The boulders were not just lying around like so many building blocks on the empty plain. Thousands of people had to haul them from somewhere, without wagons, trucks, cranes, and this, in itself, is an astonishing story.

The bluestones at Stonehenge comprise five different types of stone. Dr. Herbert Thomas of the British Geological Survey established in 1923 that in only one region do the three most dominent types occur together naturally, the other two appearing nearby. This region is the Prescelly Mountains of Wales, 130 miles from Stonehenge as the crow flies, 240 miles by the sea and land route probably taken by those early builders.

This route went southwest to Milford Haven (where the mica sandstone of the altar stone is found), along the coast in the Bristol Channel, up the Avon and Frome rivers, overland to the Wylye River, down this waterway to Amesbury, and along an avenue to Stonehenge-25 land miles, 215 water miles. The latter, by far the easiest part, was probably accomplished with a number of rafts or simple canoes, joined with crosspieces, poled along by several men. In 1954 the BBC broadcast a reenactment of the transporting of the stones, using concrete replicas. The experiment determined that 24 men were required to haul a 3,500-pound load up a 4° slope-16 men per ton—using a system of sledges and rollers, the same method used in the construction of the Egyptian pyramids. While one team strained on ropes of twisted hide attached to the sledges, others had to continually advance the rollers from back to front, and also clear the way.

If hauling the bluestones seems arduous, imagine the task of dragging 80 sarsen stones, averaging 30 tons each, 20 miles from the Marlborough Downs north of Stonehenge. Here the sandstone boulders are plentiful and little quarrying was required. The stones were sized roughly, then cut either by sharp wedges inserted into cracks or by hot and cold stresses applied along a break line, followed by bashing with 60-pound stones. Then the boulders were mounted on sledges. Using the formula of 16 men per ton, Hawkins estimates that 800 men were needed to haul the sarsens, with 200 more on hand to move the rollers—that a total of 1,000 haulers worked seven full years to accomplish the task.

At the Stonehenge site the builders dressed and polished the stones using mauls and other rough stone tools. Atkinson estimates that the 3 million cubic inches of stone removed from the sarsens, (and there may have been more) through bashing and grinding occupied 1 million man-hours of labor.

To erect the unwieldy stones, a hole was dug, the depth depending on the size of the stone. (In some cases, the above ground portion of the stones had to be uniform.) An angle of 45° was formed on one side of the hole, thus creating a ramp along which to slide the stone. Wooden stakes were placed in the hole opposite the ramp to protect that side from the end of the stone.

A team of 200 men rolled the stone over the hole, tipped it down the ramp, then heaved it up using ropes attached to the upper end of the stone and run through a high wooden scaffolding opposite the ramp. Or, at this point, the stone may have been levered into place by gradually building up a fulcrum of stones and wood. Once it was in place, the surrounding hole was rapidly filled and the stone allowed to settle for some months. The placement of lintels was more awesome still.

A massive ramp of earth may have been engineered and the lintels pushed and pulled and dragged with ropes up the 40° incline to the top of the uprights. But since no archaeological evidence exists for these mounds, a more likely method was the use of a latticework made of logs.

A lintel was positioned in front of two uprights and two logs placed perpendicular to it. The rock was then rolled onto the logs, and an extension of the logs was added.where the stone had been. On top of this the workers laid two more layers of logs, the first parallel and the second perpendicular to the lintel. The huge stone was rolled to this higher platform and another, still higher, was constructed. After rolling the lintel countless times, the lattice tower was as high as the uprights and the lintel could be properly placed, the holes fitting over the knobs.

In all, Hawkins estimates, a total of 1.5 million man-days of labor were necessary to erect the beautiful and mysterious monument.