Ball bearings and Stonehenge

NOVA aired another program about Stonehenge but this time a unique twist was included regarding the function of a number of precise granite spheres...about three to four inches in diameter. What were they for...huge slingshots? It was suggested that these stones were used as ball bearings secured in a wood channel [like railroad track] upon which a sled was used to haul the mammoth blue stone from quarry to building site. With a large quantity of man power the stones would ride upon the granite ball bearings with ease.

Transcript...

"Secrets of Stonehenge"

November 16th, 2010

NARRATOR: Every year, a million people descend on Stonehenge. They ask the age-old questions about this mysterious monument: Who built it? How was it built? And why?

To find out, archaeologists are studying Stonehenge with new tools and new eyes.

COLIN RICHARDS (The University of Manchester): By constructing Stonehenge, these people were creating something which had never been created before. It's a bit like this was their own space program.

NARRATOR: There's a new theory about the meaning of Stonehenge.

MIKE PARKER PEARSON (The University of Sheffield): It's about the nature of eternity and the meaning of life and death.

MIKE PITTS (British Archaeology): A lot of bone here.

JACQUELINE MCKINLEY (Wessex Archaeology): …nice long piece of fibula.

I think we're going to get at least 50 individuals in here.

NARRATOR: An ancient world is coming back to life.

MIKE PITTS: This is an extraordinary time for Stonehenge. We're beginning to understand it in a way we've never been able to do before.

NARRATOR: The Secrets of Stonehenge, revealed, right now on NOVA.

Brooding and majestic, Stonehenge is an icon of prehistory. It dates back to a time before Egypt built its pyramids, to the Stone Age in Britain. Time has taken its toll, but this monument remains a marvel of ancient engineering.

A circular ditch and bank surround the stones. Upright stones tower over 20 feet and weigh up to 45 tons. Horizontal slabs, called lintels, crown huge pillars.

All these giants are made of sarsen, a local sandstone, harder than granite. Yet they were carved and fitted like woodwork. Uprights were tapered and topped with knobs. These fit hollows on the bottoms of lintels.

Curved lintels, joined by tongue-and-groove, formed a nearly perfect circle. And despite a slight slope, this ring of lintels was level to within inches.

The sarsens dominate Stonehenge, but nestled among them are smaller stones, no less remarkable. Geologists determined these are bluestones, transported here from Wales, at least 150 miles away.

Who built Stonehenge? How was it built? And why? For ages, we could only wonder. Now, a new age is beginning.

An army of archaeologists deploys around Stonehenge.

MIKE PARKER PEARSON: Okay, everybody.

NARRATOR: Led by Mike Parker Pearson, the Stonehenge Riverside Project is nearly 200 strong, with scientists, students and specialists in everything from astronomy to field survey.

MIKE PARKER PEARSON: We're six years into this archeological project. It's one of the biggest in the world, I reckon, so, it's a really big chance to find out some of the key questions about Stonehenge. We're on a mission; we're on a quest.

NARRATOR: It's a quest to reconstruct the ancient world that gave rise to Stonehenge and resurrect the people who built it. The strategy is to dig, not just at Stonehenge, but throughout the surrounding landscape.

Stonehenge, itself, was extensively excavated during the twentieth century. Those digs established that the monument was built in stages. Prehistoric people chose a rolling stretch of Salisbury Plain. And, around 3000 B.C., they dug a ditch, a bank and a ring of 56 pits, into the underlying chalk of the plain.

These pits probably held the bluestones, brought all the way from Wales. Then, some 500 years later, the colossal sarsen stones were installed. The bluestones were pulled from their outer ring and rearranged among the sarsens. Several other stones completed the monument.

And later, parallel banks would define a processional avenue that stretched all the way from Stonehenge to the River Avon.

Twentieth-century excavations also uncovered the dead of Stonehenge. In the 1920s, nearly 60 human burials were excavated here, many in that outer ring of 56 pits, known as the Aubrey Holes. But the discoveries were hardly acknowledged, because these were cremation burials.

MIKE PITTS: These people had been cremated, so they didn't have nice skulls with gleaming teeth to display. They had bundles of ash and bits of broken burnt bone. The archeologists weren't interested in those as objects. At that time, it was firmly believed that there was nothing you could learn from looking at cremated bone.

NARRATOR: Not a single museum in Britain wanted the bones, so, in 1935, they were reburied in Aubrey Hole Number 7.

MIKE PITTS: The idea that Stonehenge was actually, one of, if not the biggest cremation cemetery in early prehistoric Europe, just disappeared into the ground, into Aubrey Hole 7, and was forgotten about.

NARRATOR: The bones were left undisturbed, until today. Mike Parker Pearson has come to retrieve the dead of Stonehenge. To him, they represent a treasure trove of information.

MIKE PARKER PEARSON: With closer analysis of those remains, even though they're burnt, we can work out people's approximate ages; we may be able to work out if they're male or female; we may even be able to find out more about their standard of life. So, it's a really important opportunity to learn about the Stonehenge people.

NARRATOR: Records from 1935 state the bones were placed in four burlap bags and buried with a commemorative plaque.

MIKE PITTS: It's the first time anyone has seen a decent Aubrey Hole for a good 80 years. It's quite impressive. But it's what's underneath, lower down, that we're most interested in. And we're getting close.

JULIAN RICHARDS: Oh, look.

MIKE PITTS: What's that? Is it...?

NARRATOR: Suddenly they spot a tiny piece of bone.

MIKE PITTS: Yep, it's burnt bone. Yeah.

JULIAN RICHARDS: Oh, look. There's more. It's all over the place.

NARRATOR: The burlap bags that contained the bones have rotted away.

MIKE PARKER PEARSON: I think we've just got to very carefully loosen the soil bit by bit.

Is it desperately uncomfortable?

MIKE PITTS: Yes, it is, quite.

MIKE PARKER PEARSON: So we're just going to take it in turns, as long as each of us can stand it.

JULIAN RICHARDS: Till the blood rushes to your head and you start to feel faint.

MIKE PARKER PEARSON: That's already happened.

Oh, here we go. Here we go.

MIKE PITTS: Oh, look at what I found!

MIKE PARKER PEARSON: The plaque! There it is. Read it out.

JULIAN RICHARDS: "Most of these bones were dug up in the years 1921, 1922, 1923, reburied in 1935."

MIKE PITTS: Yeah, but actually it doesn't tell us anything we don't know, does it?

JULIAN RICHARDS: I know. But isn't it nice?

MIKE PARKER PEARSON: We've finally reached the bone layer. I think we were all hoping that the two men who buried these bones for posterity would actually have put them in decent containers. But all we're really looking at is very loose cremated bone.

JULIAN RICHARDS: Oh, crikey! Look at that.

MIKE PITTS: Looks like a lot of bone.

We've lifted the plaque, and what we saw was quite a shock. It's just a complete jumbled mess of bone, from who knows how many people. The plaque has stopped soil falling down in amongst them. So as the sack rotted, the bones were left completely clean. But it's going to be a serious jigsaw puzzle in the lab.

MIKE PARKER PEARSON: I was hoping it was going to be easy, but this is the worst-case scenario.

NARRATOR: Little remains of the people of Stonehenge. What do we know of their world?

Around 3000 B.C., the Age of the Pharaohs begins, in Egypt. The first cities are flourishing in the Near East, with writing and wheeled vehicles. The use of metal is spreading across Europe but has yet to reach Britain. Here, the Stone Age is in its final phase, the Neolithic. The stone ax reigns supreme. With this tool, people clear forests and shape the timbers of their homes. Their settlements are small and scattered. They keep livestock, and move with their herds. They raise barley and wheat.

JACQUELINE MCKINLEY: People tend to get the impression that in the Neolithic, the late Stone Age, life is grim and short. That's not necessarily the case at all. People generally seem to have been probably fairly well-nourished; they would have had access to quite good food resources. They were obviously sophisticated, and they're probably having a fairly good lifestyle.

NARRATOR: Their stone tools and fine pottery have survived the ages. But objects crafted of wood, plant fibers or leather have mostly vanished, in Britain's climate and soil. The fabric of their daily lives, their customs and their beliefs have long eluded us, but the remains of their dead are providing new clues.

At Aubrey Hole Number 7, Jacqueline McKinley joins the excavation effort. An expert on ancient human remains, she quickly spots individual features.

JACQUELINE MCKINLEY: That's a nice long piece of fibula; brilliant. Probably second or third molar; that's the back of skull; look. In fact, that's a chap; that's a male; jolly good.

It's a very important collection. We're in a very important place. And although it looks like a mess, by separating out the different skeletal elements, we can work out how many people there were in there, and the sex and the age of those individuals.

And looking at amount of material we've got, I would think we're going to get at least 50 individuals in here.

NARRATOR: In all, 35 pounds of cremated bone are eventually sent to the University of Sheffield.

Graduate student Christi Cox is resurrecting the dead of Stonehenge, bit by bit.

CHRISTIE COX (The University of Sheffield): There's thousands and thousands of bone pieces. It's far more than we ever anticipated when we originally started the excavation.

JACQUELINE MCKINLEY: This should join here. That is just amazing. So we're looking at this bit down the side here, where the mandible joins...

CHRISTIE COX: So, the T.M.J. joint?

JACQUELINE MCKINLEY: Yeah, so that suggests that we've got an older individual.

NARRATOR: The bones reveal that burial at Stonehenge was reserved for a select group.

JACQUELINE MCKINLEY: With a normal domestic cemetery, you'd expect to find a range of ages and individuals of both sex. But most of the cremated bones are from adults, and the majority of those adults appear to be male, and mostly within the 25 to 40-year age group.

CHRISTIE COX: We're seeing just a slight wear and tear on the bones in this population. So they were fairly healthy; they were fairly robust male individuals.

JACQUELINE MCKINLEY: If you've mostly got male cremations in there, that's something odd. That means that certain people are being selected for burial here. What was special about them?

MIKE PARKER PEARSON: I suspect they may well have been people of important political stature, quite possibly the men in one or more royal lineages, whose authority made Stonehenge possible in the first place.

MIKE PITTS: So, what this could be indicating is, actually, at the time that Stonehenge was built, we have an, an aristocratic male-based society. Now, that's something we would never have known without these bones.

NARRATOR: Perhaps one royal family marshaled the manpower to create Stonehenge. And across the British Isles, other families or clans built their own stone circles. Nearly a thousand still stand today.

Neolithic people also raised timber circles.

Today, all that remains are traces of postholes, but their size indicates some held tree trunks 15 feet high, weighing several tons. Enormous pits were dug to hold these timbers and standing stones. And many circles were enclosed by a circular ditch and bank, an earthwork known as a "henge."

How did people with Stone Age technology manage to build on such a vast scale?

Near Stonehenge, Parker Pearson's team excavates a prehistoric ditch, carved into the chalk of Salisbury Plain. Suddenly, an ancient digging tool comes to light.

JULIAN THOMAS (The University of Manchester): Oh! Oh, look at that!

NARRATOR: It's a pick made from the antler of a red deer.

JULIAN THOMAS: Antler picks were used as the means of excavating these features—ditches, pits—during the Neolithic. You can imagine people using these picks to lever out great chunks of chalk, prizing it out and then putting it into baskets and pulling it out of the hole, an enormously labor-intensive task.

When they got to the bottom, when they finished, maybe it was broken, and they just dropped it, or maybe they just deliberately left it there, almost as an offering.

NARRATOR: But how did people move the giant sarsens, up to 45 tons of solid rock? How did they raise lintels to the tops of those gate-like structures called trilithons?

To archaeologist Mike Pitts, the process involved manpower and myth.

MIKE PITTS: We're about 20 miles north of Stonehenge, and this area is probably where all the big stones, the sarsens, at Stonehenge came from. This landscape now looks very much as I think it would have been in the Neolithic. So we have the trees, we have the forests growing, expressing life, and we have the stones, in thousands, lying largely under the ground, like bodies. These are places that could be repositories of superstition, of myth and fear and danger.

NARRATOR: To find a sarsen of the right size and shape for Stonehenge may have been a sacred quest for the most skilled stone masons.

MIKE PITTS: Like a Michelangelo, they'd examine the stone very carefully. These are guys that are used to making stone tools, they understand stone. And I think a Stonehenge mason would have looked at a stone like this as something that he's used to making, like a stone ax or an arrowhead, but enlarged into a huge scale.

NARRATOR: Masons may have roughly shaped the sarsens at the quarry site, using pounding stones. But they left few clues to how they moved and raised giant stones.

LEADER (Dramatization of Stonehenge masons gathering stones): One, two, three, four!

NARRATOR: So researchers have experimented.

Stone Age Britain did not have the wheel, but people may have pulled large stones over rollers made of tree trunks. Perhaps they laid timber tracks and slathered them with grease. A wooden sled with a keel would have kept the stone centered over the tracks. Raising a giant stone involved somehow tipping it into a giant hole. Lintels may have been pulled up ramps and levered into place. All these techniques are plausible. There's just no evidence they were actually used.

Now there's a new theory.

Andrew Young became obsessed with carved stone balls during graduate work at the University of Exeter. Some of these prehistoric objects are elaborately engraved, but many are unadorned.

Most have been found in northeast Scotland, an area known for its stone circles. These artifacts defy explanation.

ANDREW YOUNG (The University of Exeter): People had said they might be weapons or for throwing or, uh, possibly pounding vegetables, kinds of things that you could do with portable stone objects. Nothing that anybody had really said about them satisfied my question: "What are they for?"

NARRATOR: Young taught himself to carve replicas and pondered one strange fact. Many carved balls, engraved and plain, have exactly the same diameter.

ANDY YOUNG: Large numbers are identical in size, to the millimeter. And why would they need to be identical in size? And that just gave me that eureka moment. "Wow. If you're going to use them as a wheel you need them to be the same size."

NARRATOR: Andrew Young had a vision of Stone Age ball-bearing technology. For his Ph.D. thesis, he's testing his idea at a farm near Stonehenge.

ANDY YOUNG: So, this one's high.

NARRATOR: He's joined by a team of fellow students and his graduate advisor, Bruce Bradley, an authority on experimental archaeology.

BRUCE BRADLEY (The University of Exeter): All right, let's move them back towards each other.

Andy brought this theory to me. I was astounded, because it just made sense. It's just so obvious. Why didn't somebody think of this before?

NARRATOR: With rails made of Douglas fir, they'll build 80 feet of track.

ANDY YOUNG: It's not straight, though.

NARRATOR: Each rail has a channel cut into it to hold granite balls, hand-finished to a precise 75-millimeter diameter.

They'll also use wooden balls. During the time of Stonehenge, people were skilled at carving stone and wood, and could have produced all these components.

ANDY YOUNG: That's a lot better.

NARRATOR: Instead of a giant stone, the team has twenty-five tons of gravel.

And Andrew Young has his concerns.

ANDY YOUNG: I'm really worried about the type of wood we used. They would probably have used oak in the Neolithic. We haven't been able to use oak because of the cost. The wood we've got is perhaps too soft.

NARRATOR: They build a platform, a crib, to straddle the rails and carry the weight.

BRUCE BRADLEY: The worst fear would be that we'd get just a couple of tons on there and we couldn't push it anywhere. There's a lot of unknowns right now, and that's what experiments are all about.

NARRATOR: They load 3.3 tons, roughly the weight of a bluestone at Stonehenge.

BRUCE BRADLEY: One, two, three, go! Keep it going, keep it going! Oh, darn.

NARRATOR: Almost immediately, they're stuck.

BRUCE BRADLEY: Man, what happened?

NARRATOR: The weight is crushing the Douglas fir.

BRUCE BRADLEY: This amount of weight seems to have compressed it enough that our gap…we're losing our gap.

ANDY YOUNG: It's less than a centimeter, and that is not good.

BRUCE BRADLEY: No.

ANDY YOUNG: As soon as you've got that crib touching the rail, you've just got friction. You've totally undermined everything we've done with the balls.

NARRATOR: Young's worst fear about the soft wood has come true.

But there's a quick fix. To offset the compression of the Douglas fir, they place wooden inserts in the grooves.

BRUCE BRADLEY: Eastern, 23 mil.

NARRATOR: The gap is back, at least for now.

They load up nearly six tons, roughly the weight of two bluestones. Can they do it?

BRUCE BRADLEY: Look at the division of labor all of a sudden. How did that happen?

ANDY YOUNG: Hey, you girls, the call will be "giddyup."

BRUCE BRADLEY: All right. One, two, three, go!

ANDY YOUNG: Keep going, folks.

BRUCE BRADLEY: Keep at it. Let's get on those wooden balls.

We're gaining speed.

Whoa!

ANDY YOUNG: We've moved the bluestones, and once it was going, we were going.

BRUCE BRADLEY: Yeah, we were having a hard time stopping.

ANDY YOUNG: We're not as heavy as the sarsens at Stonehenge, but I'm convinced that's it. We can move the sarsens, no problem.

NARRATOR: The largest sarsen at Stonehenge weighs some 45 tons. How much can this rig handle? The team has one more day to find out.

Moving the sarsens was just one challenge for the builders of Stonehenge. They also had to carve these giants to fit together. How did they achieve such precision?

Just outside Stonehenge, Parker Pearson's team noticed small pieces of sarsen emerging from, of all things, mole hills.

MIKE PARKER PEARSON: The little molehills allowed us to see that there was sarsen under the ground, those little chips were dug up by these little furry creatures.

NARRATOR: A small trench revealed an astonishing carpet of stone fragments, debris from the dressing of giant stones.

MIKE PARKER PEARSON: The stone dressing trench has produced fantastic surprises. This is where the stones were lying and having their faces trimmed and bashed. And we've been able to find, in that tiny trench, 50 hammer stones.

COLIN RICHARDS: This is the hammer stone. Actually fits quite nicely in the hand, as it turns out. And you can see all the pitting around the outside, where it's been banging against something. The Neolithic builder would literally have stood alongside the stone to do the more fine-scale work. This is going to take ages, just to get that fine, fine shape.

Stonehenge is an expenditure of labor on a grand scale. You know, it's easy for us to forget just that these people were creating something which had never been created before. It's a bit like their own space program.

NARRATOR: Stonehenge is a masterpiece of Stone Age technology. But what did it mean to the people who built it? Was it simply the burial ground of a royal family, or was there more to the monument?

An enduring theory about the meaning of Stonehenge dates back to an observation made by 18th century scholars. They noticed that the entrance to Stonehenge faces the rising sun on the longest day of the year, the summer solstice.

By the 1960s, people had embraced the monument as an observatory used by ancient astronomers to track the sun and moon. Some astronomers even claimed the mystery of Stonehenge had been solved.

CLIVE RUGGLES (University of Leicester): Well, let's get one thing clear, this wasn't some sort of astronomical instrument.

NARRATOR: Clive Ruggles has written the book on ancient astronomy. An archaeologist and astronomer, he ran his own studies of Stonehenge.

CLIVE RUGGLES: Everyone thinks that it's some sort of ancient observatory that incorporated lots of alignments. In fact, we archeologists are only confident in one alignment at this monument, and that was the main axis that you see here.

NARRATOR: This axis runs right through the center of Stonehenge and down its avenue. In this direction, it points at sunrise, on the summer solstice, around June 21st.

CLIVE RUGGLES: On those few days around the longest day of the year, just as the sun rises, you would have seen a shaft of sunlight coming right into this. It would have been a very spectacular effect.

The thing is, if the axis is pointing at midsummer sunrise this way, then it also has another direction.

We come round the site, you have to do a bit of imagining here, we, we've got these big trilithons, 1 and 2, standing here—there was another one standing here—we've only got one of the uprights left. Then, in fact, the axis, in this direction, points at the sunset on the shortest day of the year, midwinter sunset. So the sun would be coming down like this, and setting this direction along the axis.

NARRATOR: This extraordinary alignment sheds light on the beliefs and rituals of people in the ancient world.

CLIVE RUGGLES: Stonehenge isn't the only place that has an astronomical alignment built into it. There are many ancient peoples all over the world who have, have incorporated alignments on the Sun, the Moon, sometimes the stars.

And what it's probably telling us is a connection in people's minds between the sun and the seasonal cycle, and how, by having the right ceremonials at the right time, they could keep in harmony with the cosmos.

NARRATOR: The alignment at Stonehenge suggests the solstices were important times of year for the people who built the monument.

Mike Parker Pearson has unearthed evidence supporting that idea, though he didn't set out to study Stonehenge.

MIKE PARKER PEARSON: I never thought I'd be doing any work here, in a million years. I had many other interesting things to do, so it was a series of accidents that really led to our project getting up and running.

NARRATOR: He had spent years in Madagascar studying traditional burial practices. Here, people build stone monuments for the dead. They believe stone belongs to the realm of the ancestors. The realm of the living is built of perishable materials like wood.

In 1998, Parker Pearson happened to visit Stonehenge with an archaeologist from Madagascar.

MIKE PARKER PEARSON: When my colleague Ramilisonina saw all of this on a cold February morning, it was something of a bombshell, because what he was to say was to change archeologists' understanding of this monument completely and to lead to a huge new program of archeological research.

RAMILISONINA (Archeologist/Translated from French): I believe this is a meeting place to connect with the ancestors. I am convinced the stones are linked to the ancestors.

MIKE PARKER PEARSON: And that's the moment the lightbulb, went on in my mind, and I thought, "Stone was associated with the ancestors, the dead, and constructions in timber should be associated with the living." And this made me think a little more about what was happening in the Stonehenge landscape.

NARRATOR: He knew Stonehenge was full of cremated remains, nearly 60 burials excavated in the 20th century, and perhaps 200 more in untouched areas of the monument. If Stonehenge marked the realm of the dead, where was the realm of the living?

Less than two miles north of Stonehenge, sits the giant henge of Durrington Walls. In the 1960s, when a road was cut through this henge, archaeologists discovered the postholes of a timber circle nearly identical in size to Stonehenge.

If Durrington Walls marked the realm of the living, and Stonehenge the realm of the dead, perhaps the physical link between the two was the River Avon.

MIKE PARKER PEARSON: We know from mythologies all round the world, that water is a very important part of that journey from the world of the living to the world of the dead.

NARRATOR: It was a clever theory, with little to back it up, until excavations began at Durrington Walls.

MIKE PARKER PEARSON: My interest in Durrington Walls was to find out two things: there should be an avenue linking it to the river, just as there was Stonehenge's famous avenue leading to the water; secondly, there should be evidence of settlement, of something to do with the living.

NARRATOR: The team did uncover an avenue, some 30 feet wide, running straight from Durrington Walls to the River Avon. The dig also revealed ample evidence of the living.

MIKE PARKER PEARSON: We've actually found the floor of a house. Now, it's only four meters that way by four meters this way. It has stake holes along its sides, so…timber facade covered with chalk plaster. It's the first time we have found the floor layer for a Neolithic house anywhere in England. We can actually walk on the very surface that people walked on four and a half thousand years ago.

NARRATOR: The floors of eight other houses came to light. They were built around 2500 B.C., the same time the sarsens were put up at Stonehenge. Hundreds of other dwellings probably filled Durrington Walls, clustered around the timber circle.

MIKE PARKER PEARSON: I think we could be looking at this entire area covered in houses, perhaps, with a central open area, forming the largest village in the whole of Northern Europe at that time.

NARRATOR: But people didn't live here year-round; they came for special occasions. In between the houses, the team found huge piles of pig and cattle bones.

MIKE PARKER PEARSON: We find a lot of them still joined together, so they must have been thrown away while there was still soft tissue holding them together. What this is telling us is that these are people who are feasting.

NARRATOR: A clue to the timing of these feasts turned up in the astronomical alignment of Durrington Walls.

On the morning of the winter solstice, the timber circle pointed at the rising sun, and at the end of the day, Stonehenge framed the setting sun. Six months later, the direction was reversed. On the summer solstice, Stonehenge and its avenue aligned with sunrise, and the avenue at Durrington Walls aligned with sunset. The two monuments were linked on the summer and winter solstices.

On these days, crowds may have traveled along the river, moving between the realm of the living at Durrington Walls, and the realm of the dead at Stonehenge. Some may have cast the ashes of their dead into the sacred waters, a gesture of devotion. Perhaps royal burials were held at Stonehenge during these seasonal feasts.

MIKE PARKER PEARSON: It may just be the sense of an unending cycle that is being reenacted by this flow, back and forwards between the living and the dead, to enable society to keep going.

NARRATOR: Parker Pearson had discovered traces of an ancient belief system etched into the landscape around Stonehenge. But one question still lingered about the monument's location: why was Stonehenge built on such an unremarkable patch of countryside, not on a ridge or hilltop?

The answer may lie hidden beneath the surface of the Stonehenge avenue, the great processional route leading to the river Avon. This feature was mapped by running a small electric current through the soil and measuring its resistance. The technique can detect structures under the surface.

It picked up a series of mysterious grooves running beneath the avenue, for more than 200 yards. Parker Pearson was convinced these grooves were the remains of a manmade structure, older than the avenue.

His team opened a shallow trench to investigate.

MIKE PARKER PEARSON: I was convinced we were going to find evidence for gullies that contained vertical timber posts, something like that, and I was bitterly disappointed, because they were entirely natural.

NARRATOR: Soil specialists determined that these grooves were formed between two natural ridges in the landscape. During the last Ice Age, these ridges funneled rainwater and snowmelt between them. Yearly freezing and thawing caused the ground to crack into long deep grooves.

What makes the grooves extraordinary is that they are aligned with the solstices. On the winter solstice, they would have pointed directly at the spot where the setting sun touches the horizon.

CLIVE RUGGLES: Think about this coincidence in the landscape, the fact that you've got these natural stripes in the landscape actually aligning with the direction where the midwinter sun goes down. Yes, to us, it's a coincidence of nature, but imagine how that seemed to people whose mindset was different. It would have made it a very sacred and powerful spot. And that, for me, provides a very plausible reason why Stonehenge was constructed where it was.

NARRATOR: Prehistoric people built Stonehenge just beyond where the grooves end. Later, they enhanced the natural ridges with massive banks and extended the avenue all the way to the River Avon. Or so it was assumed.

No one had ever excavated the riverbank where the avenue ought to end, just beyond a row of country estates. So Parker Pearson brought his team.

JIM RYLATT (The University of Manchester): We came down here looking for the end of the Stonehenge avenue. And what we were expecting to find would have been fairly straightforward, just two banks and two ditches. But what we actually found was completely different.

MIKE PARKER PEARSON: What we have here is a ditch that is curving around in a semi-circle, and most likely it actually formed a complete circle. Maybe it's marking off a venerated space; maybe there's even a standing stone that once stood in this spot. Maybe there are special things here that the avenue is actually leading to, by the river.

NARRATOR: It will take more digging to get to the bottom of this mystery.

Not far from the riverside trench, Andrew Young and his team continue to test his system for moving giant stones. They tackle the equivalent of a sarsen at Stonehenge. These range from seven to more than 40 tons.

BRUCE BRADLEY: Pick up the slack! One, two, three!

NARRATOR: The team starts with a load of 8.3 tons. They give it everything they've got.

BRUCE BRADLEY: Nope. Not going. We didn't even budge it.

ANDY YOUNG: It's that moment of inertia that you've got to break, and obviously, that was beyond 10 people.

NARRATOR: Some theories claim hundreds of people were involved in pulling giant stones; Young is convinced oxen did the heavy work. For now, he'll settle for a tractor.

A gauge will measure how much force it takes to get this load moving.

BRUCE BRADLEY: There it goes. Keep it moving!

Little faster.

ANDY YOUNG: Let's have a look at that gauge.

One point two; that's very good.

NARRATOR: Young figures this would have been a snap for about a dozen oxen.

ANDY YOUNG: So what's happened there? The insert is obliterated.

NARRATOR: The spacers are breaking down.

ANDY YOUNG: It's too soft.

NARRATOR: But Young wants to try one last load.

ANDY YOUNG: What we could do is take off the top two, build the other crib and spread the weight out more, redistribute it.

BRUCE BRADLEY: I think that's the plan.

Pleased to meet you finally.

MIKE PITTS: Lovely to see you.

NARRATOR: Just then, Stonehenge expert Mike Pitts drops by.

MIKE PITTS: I've been reading your work for years, and I've always been very impressed.

BRUCE BRADLEY: Well, thank you. Thanks for bringing the rain…appreciate it!

NARRATOR: Pitts is briefed, while the team sets up a second crib.

MIKE PITTS: What I'm thinking as I look at this, I'm thinking, okay, supposing this did happen, you've got to have a really smooth track, like a road.

BRUCE BRADLEY: Absolutely.

MIKE PITTS: You need an engineered route again, almost.

BRUCE BRADLEY: Yeah, basically. It's pretty sophisticated.

MIKE PITTS: Yeah, but I can't believe that in the Neolithic, when they were moving these stones, that the landscape would be nice and clear and smooth like this. There's going to be all sorts of things going on: swamp and forest and stones getting in the way. And the steep slopes that you've got to get through.

BRUCE BRADLEY: But that's the case with any system. That doesn't make it unique to this one.

MIKE PITTS: Absolutely, absolutely.

NARRATOR: Now, the rig is ready for a final run: nearly 13 tons; heavier than some sarsens at Stonehenge; about a third the weight of the monument's largest stones.

BRUCE BRADLEY: There it goes. Keep it going. Keep it going. Keep it going. Uh-oh, stop! Stop!

ANDY YOUNG: What happened?

BRUCE BRADLEY: Something happened. It just sort of went down, and I think it went down... I don't know where it went down.

ANDY YOUNG: The wood's bent now.

BRUCE BRADLEY: Yeah, but it worked. I don't know about you, but I was pleased with that. I think we're done, 'cause we can't stay out here and get everybody frozen.

NARRATOR: The skies clear for a few afterthoughts.

MIKE PITTS: I'm not at all convinced. I think it's too sophisticated. We don't need that level of complexity to move Stonehenge, the more complex you make it, the more likely it is to go wrong.

BRUCE BRADLEY: I think a lot of times we think of people that live in simple cultures, as we define them, don't have a science because it's not written down or it's not formulaic. But these people's technology is their science.

ANDY YOUNG: I'm satisfied that my initial idea seems to work on a big scale. So, I'm just happy it's all done gone the way it has, because you don't know until you try.

NARRATOR: For all we know, the builders of Stonehenge used techniques no modern researcher has yet imagined. If only we could excavate the Neolithic mind.

Back at the riverside, Parker Pearson and his team expand their trenches and expose more of that strange circular structure. It appears to be the ditch and eroded bank of a henge.

MIKE PARKER PEARSON: Ben, we have a huge triangular stone hole in that one.

NARRATOR: In its center, they make a spectacular discovery: a ring of large holes.

Recorded in a laser scan, their shape and size point to one thing: they probably held bluestones, just like the ones now standing at Stonehenge.

MIKE PARKER PEARSON: This place was selected out as a special spot to build a stone circle. And, to do that with antler picks, they had to dig a circle of holes. And the hole in front of me, they've created almost a nest of flint nodules to form a base to support the stone coming in on top of it. So, these stones would have formed almost a mini-Stonehenge, without the lintels, very close together, standing some three meters high in places.

NARRATOR: The complete circle probably held 25 stones. The team names it "Bluestonehenge."

MIKE PARKER PEARSON: So, when was it put up? When was it taken down? Where did the stones go?

And we're starting to get some answers for those questions.

NARRATOR: Found in the stone holes, a distinctive type of arrowhead suggests Bluestonehenge may have been built around 3000 B.C.—at the same time Stonehenge was first built—as a ring of 56 bluestones. The two monuments may have been linked from the start.

MIKE PARKER PEARSON: It may well be that these were set up together, as two separate stone circles: one right by the river, one up at the special solstice place of Stonehenge itself, so, providing the two ends of a ceremonial route for people to move back and forwards.

NARRATOR: But what happened to the bluestones by the river?

Parker Pearson believes they were moved to Stonehenge. This probably happened around 2500 B.C., when the giant sarsens were installed in the center of the monument.

But the bluestones still mattered. They were pulled from the Aubrey Holes and the riverside, and rearranged, perhaps enshrined, inside the sarsens.

To the people who built and rebuilt Stonehenge, what did the bluestones mean? Why were dozens gathered from these outcrops in Wales, at least 150 miles away?

Some of Britain's first farmers put down roots in Wales a thousand years before Stonehenge was created. Parker Pearson believes their descendants brought the bluestones to Salisbury Plain.

MIKE PARKER PEARSON: When you actually move a stone, you're planting your identity, your very ancestry into the ground. You're saying, "Yes, we used to come from over there, but this is our place, and these are the symbol that even our ancestors occupy this space." So, what I think we're seeing is that sense of transferring one's ancestors and ancestry in the form of stones, and here we have this very expression of belonging.

NARRATOR: Around 2500 B.C., Stonehenge became a monument like no other, a symbol of everything the Stone Age could achieve.

MIKE PARKER PEARSON: But this is one of the last great monuments to be built in southern Britain. It's the end of an era rather than the flowering of a huge powerful civilization. It's something of a swan song.

NARRATOR: As Stonehenge reaches its peak, something new is trickling into Britain: copper, gold and, later, bronze. For people who define their existence in terms of stone and wood, metal changes nearly everything. With metal comes a focus on personal wealth and status. Now the dead are laid to rest with their riches, in individual burial mounds—hundreds appear in the landscape around Stonehenge—and the age of grand communal monuments comes to an end.

A symbol of eternity, Stonehenge was built to stand forever, but, in time, the great stone circle was abandoned. Its age was eclipsed by a new technology, a new way of being. And that is a story as old as the hills.