Secret of El Dorado The Secret of El Dorado - programme summary

In 1542, the Spanish Conquistador, Francisco de Orellana ventured along the Rio Negro, one of the Amazon Basin's great rivers. Hunting a hidden city of gold, his expedition found a network of farms, villages and even huge walled cities. At least that is what he told an eager audience on his return to Spain.

The prospect of gold drew others to explore the region, but none could find the people of whom the first Conquistadors had spoken. The missionaries who followed a century later reported finding just isolated tribes of hunter-gatherers. Orellana's story seemed to be no more than a fanciful myth.

A proven liar?

When scientists came to weigh up the credibility of Orellana's words, they reached the same conclusion. As productive as the rainforest may appear, the soil it stands in is unsuited to farming. It is established belief that all early civilisations have agriculture at their hearts. Any major population centre will have connections with a system of intensive agriculture. If a soil cannot support crops sufficient to feed a large number of people, then that serves as an effective cap on the population in that area. Even modern chemicals and techniques have failed to generate significant food from Amazonian soil in a sustainable way . The thought that indigenous people could have survived in any number - let alone prospered - was dismissed by most scientists. Scientific consensus was sure that the original Amazonians lived in small semi-nomadic bands and that Orellana must have lied.

Clues from the Bolivian savannah

Bolivia's Llanos de Mojos (Mojos Plains) are 2,000km from Orellana's route down the main channel of the Amazon. The terrain is savannah grassland with extreme seasons - floods in the wet; fires in the dry. Crops are hard to grow and few people live there. But back in the 1960s archaeologist Bill Denevan noted that the landscape was crossed with unnaturally straight lines. Large areas were also covered with striped patterns.

Recently, Denevan's work has been followed up by Clark Erickson, a landscape archaeologist. His attention was drawn to the numerous forest islands dotted across the savannah like oases. Down on the ground he found them littered with prehistoric pot sherds, a clear sign of early human habitation. Some mounds were as much as 18m high and much of the pottery was on a grand scale as well. Such huge vessels were too big for wandering nomads. Here were permanent settlements, where hundreds or even thousands of people had once gathered for huge ceremonies. To Erickson, these were signs of an advanced society - a civilisation.

Erickson and a colleague, William Balée, needed evidence for organised farming and found help working with the region's Amerindians. Some of the mounds are still inhabited by indigenous people. The language of the Sirionó offers clues to their past. Words for staple crops like maize, as well as cotton and dye plants, hint at what may have been farmed hundreds, even thousands, of years ago.

Erickson's interpretation of the lie of the land is that the mounds were built to offer protection from floodwaters, with the most sacred buildings always at the centre of the mound on the highest level. There is historical evidence for this - a Spanish expedition of 1617 remarked on the extent and high quality of a network of raised causeways connecting villages together. Those causeways can still be seen as straight lines cutting across the savannah. Alongside them run canals, a result of their construction.

Denevan and Erickson have shown that the striped patterns are relics of a system of raised fields. From the air, the area which appears to have been turned over to such agriculture is clear. It covers thousands of square kilometres. In conjunction with the controlled irrigation a canal network might offer, it could have sustained hundreds of thousands of people. Erickson believes the Mojos Plains were home to a society which had totally mastered its environment.

If land now little suited to agriculture could once have supported hordes of people, is there a chance Orellana's mythical El Dorado has some basis in fact?

When anthropologist Michael Heckenberger met the Kuikuru tribe in the central Amazon he was impressed by the complexity of their social structure. Why, he wondered, would a tribe of just 300 people adopt such a hierarchical way of life? (Received opinion held that Amazonian tribes were small, egalitarian societies.) He found evidence that the Kuikuru had once lived in an integrated network of villages, each one many times the size of their modern-day

settlements. Heckenberger believes the prehistoric Kuikuru were not the semi-nomadic wanderers of anthropological theory. Instead, they lived in large chiefdoms - the advanced society described by Orellana.

The secret of the soil

The search for clues in the Amazon takes place at grass roots level - in the soil itself. Along Brazil's Tapajos River, archaeologist Bill Woods has mapped numerous prehistoric sites, some with exquisite, 2,000 year old pottery. There is a common thread: the earth where people have lived is much darker than the rainforest soil nearby. Closer investigation showed that the two soils are the same, the dark loam is just a result of adding biological matter. The Brazilians call this fertile ground terra preta. It is renowned for its productivity and even sold by local people.

Archaeologists have surveyed the distribution of terra preta and found it correlates favourably with the places Orellana reported back in the 16th century. The land area is immense - twice the size of the UK. It seems the prehistoric Amazonian peoples transformed the earth beneath their feet. The terra preta could have sustained permanent intensive agriculture, which in turn would have fostered the development of advanced societies. Archaeologists like Bill Petersen, from the University of Vermont, now regard Orellana's account as highly plausible. But if the first Conquistadors told the truth, what became of the people they described?

Tragically, the visitors brought diseases to which the Amerindians had little resistance: smallpox, influenza, measles. Orellana and his men were the first and last Europeans to set eyes on an Amazonian civilisation. They themselves may have been the ones to trigger its rapid decline.

Yet the Amazonians' greatest achievement lives on. Soil scientists analysing the terra preta have found its characteristics astonishing, especially its ability to maintain nutrient levels over hundreds of years. 20th century techniques of farming on cleared, torched rainforest - so-called slash and burn agriculture - have never been sustainable. With the vegetation burned off, the high rainfall soon leaches all the nutrients out of the soil. Research has shown that even chemical fertilisers cannot maintain crop yields into a third consecutive growing season, yet terra preta remains fertile year after year.

Nature and nurture

Again, Orellana's accounts offer potential insight. He reported that the indigenous people used fire to clear their fields. Bruno Glaser, from the University of Bayreuth, has found that terra preta is rich in charcoal, incompletely burnt wood. He believes it acts to hold the nutrients in the soil and sustain its fertility from year to year. This is the great secret of the early Amazonians: how to nurture the soil towards lasting productivity. In experimental plots, adding a combination of charcoal and fertiliser into the rainforest soil boosted yields by 880% compared with fertiliser alone.

Yet terra preta may have a still more remarkable ability. Almost as if alive, it appears to reproduce. Bill Woods has met local farmers who mine the soil commercially. They find that, as long as 20cm of terra preta is left undisturbed, the bed will regenerate over a period of about 20 years. He suspects that a combination of bacteria and fungi is causing this effect.

Today, scientists are busy searching for the biological cocktail that makes barren earth productive. If they can succeed in recreating the Amerindians' terra preta, then a legacy more precious than the gold the Conquistadors sought could spare the rainforest from destruction and help feed people across the developing world.

Questions and answers

The Secret of El Dorado - questions and answersIs there only one account (Francisco de Orellana's) that refers to an Amazonian El Dorado?

Orellana actually never mentions El Dorado by name. He was part of an expedition to find a wealthy kingdom in the jungles of present day Ecuador. The Conquistadors had heard the Indians tell of such a kingdom, but it's not clear that they associated it with the legend of El Dorado ('the gilded one'). He and his men became separated from the main group and swept into the Amazonian river system. They floated all the way to the Atlantic, describing many large kingdoms, towns and even cities along the way. Orellana (or rather his chronicler, the expedition's priest, Gaspar de Carvajal) claimed that the Indians talked of kingdoms further inland where there was much gold, but he never claimed to have seen any himself. It was twenty years before any other Europeans attempted to explore the central Amazon, and their accounts of the region are very different.

Is it archaeologists' belief that the Amerindians did not build huge structures or is the erosion in the Amazon greater than that further north where - for example - Mayan temples still stand?

There is practically no stone in the Amazon Basin, and so the Amazonians built in wood. Of course, this quickly decays in the tropics - in just a few years it's all eaten by insects. The Amazonians did move earth on a large scale, however, and some very impressive monuments are now coming to light as areas of forest are cleared. The mounds and causeways are difficult to discern under forest canopy, of course.

Over what historical time period does the generation of terra preta (the fertile, artificial, dark earth) extend?

Eduardo Neves has been using radiocarbon dating to date terra preta sites. So far a clear pattern emerges - the terra preta seems to start around the time of Christ, perhaps a few hundred years earlier. This is the same time that archaeologists first see complex polychrome pottery and evidence of mound building, both in the Llanos de Mojos and on Marajó island at the mouth of the Amazon.

How valid is it to extrapolate from aerial mapping of terra preta plots to areas of civilisation?

Most archaeologists now agree that terra preta is an anthrosol, ie an artificial soil. So there is little doubt that where there is terra preta there was once human activity.

Can we be sure people weren't nomadically wandering from one terra preta mound to another, ie that fewer people were being supported by the soil?

Again, Eduardo Neves has used carbon dating to estimate the rate of terra preta formation. He finds that a metre of soil was produced in just a few decades. This is a very fast rate of soil formation, and Neves believes that this is evidence that the occupation that produced it was intense and continuous. It's fair to say that some scientists take a different view. Betty Meggers in particular holds to the view that the occupation was sporadic and shifting, and that very high population estimates are therefore unjustifiable. This is probably the minority view today.

How long does terra preta take to develop from normal jungle/savannah earth?

We have yet to succeed in making terra preta ourselves, but perhaps we could do it faster than the Indians if we can get to understand what the key ingredients are.

Is there anything at all special about the charcoal that seems to create terra preta?

No.

What has been the attitude of governments etc in the Amazon region to these studies?

The Brazilian government has been making increasing efforts in recent years to preserve and protect its native patrimony. IMBRAPA, the government-funded agricultural research institute is now heavily involved in terra preta research.

Who will benefit most if the bio/chemical secret of terra preta is ultimately unlocked?

It could have profound effects on tropical agriculture, especially in light of a worldwide crisis in soil fertility. Terra preta seems especially suitable for the cultivation of fruit and vegetables, what we would call market gardening. These crops have high economic and nutritional value for poor farmers in the developing world, and they would be the main beneficiaries if it could be recreated on a wide scale. There would be environmental benefits as well. Modern agriculture in the Amazon requires heavy annual input of chemical fertilizers, and the run-off from these is now causing problems in the rivers. This is a big problem for the Kuikuru for example in the Upper Xingu valley. So called eutrophication kills fish, and the Kuikuru rely on fishing for the protein in their diet. Better soil would mean less fertilizer and healthier rivers.

What evidence is there that terra preta 'technology' is applicable the world over?

The problem with tropical soils is essentially the same all over the world. The high levels of rainfall over hundreds of thousands of years remove all the nutrients from the soil leaving only a clay substrate. This clay lacks the chemical ability to hold on to nutrients, even if they are added. This is why fertiliser doesn't work very well, and

why the charcoal may be so effective. As you may know if you take charcoal tablets for a stomach upset, charcoal is very good at absorbing things!

Can terra preta become an export 'crop' for Amerindian people instead of hardwood etc?

It's more likely that it would be made in situ than exported.

Transcript

The Secret of El Dorado - transcript

NARRATOR (JACK FORTUNE): The Amazon Basin, August 2002. This is the trail of the greatest legend of the Americas, the legend that hidden in the Amazon jungle there was once a fabulous kingdom of gold: El Dorado.

DR CLARK ERICKSON (University of Pennsylvania Museum): In the late 1500s the Spanish came here looking for El Dorado. They didn't find it, but I think it's right down there.

NARRATOR: This is the story of how archaeologists have uncovered the lost civilisation behind the myth of El Dorado, but this was not a kingdom of gold. The secret of the real El Dorado was something far more valuable, something with the power to transform our world. The story begins on the banks of the Rio Negro in the Central Amazon. A party of scientists is embarking on a voyage which they hope will provide answers to a five hundred year old mystery. They are retracing the route of the very first Europeans to penetrate the Amazon Basin, a party of Conquistadors commanded by the Spaniard Francisco de Orellana.

READER: What I shall tell will be as an eyewitness, as a man whom God chose to give a part in a strange and hitherto never experienced voyage of discovery.

NARRATOR: In 1542 Orellana led an expedition deep into the heart of the Amazon. He was searching for El Dorado, the kingdom of gold that Indians said lay hidden in the jungle. For eight months he drifted through the rainforest. When he finally returned to Spain, he brought with him spellbinding tales of an unknown civilisation.

READER: There was one town that stretched for 15 miles without any space from house to house which was a marvellous thing to behold. There were many roads here that entered into the interior of the land, very fine highways. Inland from the river at a distance of six miles more or less there could be seen some very large cities that glistened in white and besides this, the land is as fertile and as normal in appearance as our Spain.

NARRATOR: But when a few years later the Spanish returned to the Amazon in search of the kingdoms Orellana had described, they found nothing. Just a few scattered Indian settlements.

DR JAMES PETERSEN (University of Vermont): Well when Orellana came down the Solimoes and up the Negro in the area where we're passing the, it seems as if there were thousands and thousands of people, extensive villages that stretched for miles and then 20 years later, 50/60 years later, after Orellana, the, no one ever saw again what Orellana had seen and described in some detail.

NARRATOR: So the mystery is: was there really once a civilisation here, an El Dorado in the Central Amazon, or was it all just a figment of Orellana's imagination, a story made up to impress the Spanish Court?

JAMES PETERSEN: The million dollar question is: were there large and complex societies here in the Central Amazon as Orellana recorded in the 1540s. In fact it's, it's the myth of El Dorado, the myth of large, complicated Amerindian cultures here in the Amazon and the answer lies out there somewhere in, in, in the forest, in the jungle.

NARRATOR: For five hundred years the myth of El Dorado has lured adventurers and explorers into the jungles of South America and beyond the Amazon they did find wonderful things - ruined Inca citadels like Machu Picchu, hidden high in the Andes, and in Central America they found the lost cities of the Maya, but in the Central Amazon itself they have never found anything: no pyramids, no temples, just jungle, so many scientists concluded long ago that the legend of El Dorado was a gigantic wild goose chase, the province of fantasists and conmen.

PROF BETTY MEGGERS (Smithsonian Institution): Don't believe these accounts unless you can verify it archaeologically because these people had other motivations than, than the truth.

NARRATOR: Betty Meggers should know what she's talking about. She's worked in the region longer than anyone. She concluded 40 years ago that an Amazonian civilisation could never have existed and she had a compelling scientific theory to prove it. It was all to do with agriculture. Agriculture lies at the heart of all the great civilisations of the world. Only intensive agriculture produces enough food to sustain large, settled populations and only large, settled populations build cities and ceremonial centres, those defining features of civilisation. Without intensive agriculture civilisation cannot exist, but in the Amazon all attempts at intensive agriculture have led to disaster. The yellow jungle soil is just too poor. Even modern techniques have simply led to ecological catastrophe with vast swathes of forest being cleared, only for the land to be abandoned.

BETTY MEGGERS: Every effort that we've made to develop sustainable, permanent agriculture, I mean millions of dollars have been spent on efforts to do that and they've all failed and so what if, if you're going to believe that the indigenous population had a secret that, that we haven't been able to discover with all our technology and so forth and so on, you know that's fine, but what is it?

NARRATOR: Meggers's conclusion was that without advanced agriculture the people of the Amazon were simply unable to develop civilisation. The few scattered tribes were obviously a relic of an ancient way of life, nomads left behind by history.

DR MICHAEL HECKENBERGER (University of Florida): Most people have a very clear idea of what your average Amazonian looks like - small groups, more or less one with nature, what I have occasionally perhaps impolitely called Stone Age savages frozen at the dawn of time - an imagery that somehow Amazonian people represent our contemporary ancestors. They're people like us 10,000 years ago, as if they have no history.

NARRATOR: With no traces of civilisation in the Central Amazon and a compelling scientific reason for their absence, it seemed clear that Orellana must have been a liar. El Dorado could never have existed, but this traditional view of the Amazon has recently been challenged. A thousand miles from where Orellana once travelled, on the fringes of the rainforest, lie the Mojos Plains of Bolivia. What was discovered in this remote place would begin a revolution in our understanding of the prehistoric Amazon. Among those to make these discoveries was Clark Erickson, an unusual kind of archaeologist.

CLARK ERICKSON: I don't dig holes in the ground, I study landscapes. We drive over landscapes, fly over them and walk over them.

NARRATOR: Erickson has spent more than ten years studying the Mojos Plains. It's a very different environment from the Central Amazon, but just as harsh. The landscape here is dominated not by rainforest but by open grassland known as savannah. In the rainy season the savannah is flooded by several feet of water. In the summer it's dry as tinder. It makes it difficult to grow crops and hardly anyone lives here today, but then archaeologists noticed something odd about this landscape: the savannah is criss-crossed by unnatural looking straight lines and covered by mysterious striped patterns. There are also thousands of strange, isolated mounds covered in forest.

CLARK ERICKSON: A major feature on these savannahs are forest islands - the locals call them isles - and there are probably five, maybe ten thousand of these in this part of the Amazon.

NARRATOR: Erickson decided to take a closer look at these forest islands and inside every one he found the same thing: signs of human habitation.

CLARK ERICKSON: I have big debates with my natural science colleagues about the formation of these islands. They think they're natural, but I can come out here and with, usually within five minutes or so I can find a handful of pottery, or charcoal or food remains or human bone that indicate that people were here. For instance here's a, here's a fragment of, of probably a very large vessel. By the curvature here it was probably some kind of a large cooking urn, typical domestic ware you'd find on sites like this where people live.

NARRATOR: It looked to Erickson as if the thousands of forest islands were, in fact, man-made prehistoric settlements, but what kind of society had built them? Then Erickson's college William Balée took him to a site he'd found within an area of dense jungle. Hidden beneath the trees was a huge earthen mound.

CLARK ERICKSON: I remember the first time we came out here and I, we, we had no idea how big this was and it wasn't until the third or fourth day where we got the data off the computer and we could see that it was 18 metres tall. This is the highest mound in the whole area.

PROF WILLIAM BALÉE (Tulane University): Look on that palm we still have the tree tag. That's…

NARRATOR: The mound was full of ancient pottery.

WILLIAM BALÉE: …on the, on the plot as well.

CLARK ERICKSON: Well it's almost half pottery, half soil. This is the highest part of the mound and the quantity of pottery is just incredible here.

WILLIAM BALÉE: Look at this.

NARRATOR: What was striking was the size of many of the vessels.

CLARK ERICKSON: …trees around here.

WILLIAM BALÉE: Look at the size of this thing. What were they incising on the inside?

CLARK ERICKSON: Yeah this is, this is a large vessel probably about three met, a metre and a half, maybe two metres across, by the diameter of the rim here and then the grooves were placed inside when the pot, when the clay is still wet and they used this as a big grinding platform 'cos there's no stone out here.

WILLIAM BALÉE: And look, so that would have been…

NARRATOR: Vessels this large suggested this was no temporary encampment.

CLARK ERICKSON: These, we're talking about permanent settled people here. You don't, you don't carry these around on your back when you're, you're trekking or doing hunting/gathering. These are village folk and, and a lot of these were probably for cooking up not family meals, but cooking up meals for huge groups of people. We're talking maybe, you know, parties for thousands of people, so I think that that indicates that there's something going on beyond autonomous villages in this area. We also have some mounds, such as this one, that's much larger, much taller than most of the other mounds, which could be some kind of ceremonial centre or possibly a political capital.

NARRATOR: It was a revolutionary thought. Hidden beneath these trees Erickson had found a huge prehistory settlement and evidence that thousands of people had once gathered here for great ceremonies. These were the characteristics of civilisation. The first clues to what this society might have looked like came from another nearby mound called Iviato. Iviato is still inhabited, by an indigenous Indian tribe, the Sirionó.

CLARK ERICKSON: As an archaeologist this is an incredible place because here we have an archaeological site that's probably occupied 1,000, maybe 3,000 years. We still have people living on it and the Sirionó have been living here for quite a while and you get a sense of what this mound might have been like in the past.

NARRATOR: Iviato still retains its original terraced structure, with three different levels still visible.

CLARK ERICKSON: It's a 4-5m tall mound, its base is probably about maybe eight hectares or so in size. Typical you have the original surface and you come up a slight rise to a first platform here which is very badly eroded and then you come up farther to the second platform that we're standing on now and this would have been probably where most of the houses were located, many more than exist here today.

NARRATOR: Erickson believes that one thousand years ago the main platform of the mound would have been occupied by hundreds of houses and above them on the top tier the focus of the community, a sacred pyramid.

CLARK ERICKSON: Very characteristic on these mounds is that not, usually not in the centre, but at one side of the flat second terrace, or third terrace, is a pyramid-like structure of earth and today you see that the Sirionó church is on the top of here. Well we assume that in the past there probably was a temple on top, or some kind of priest's house.

NARRATOR: Here was compelling evidence that there had once been large, permanent settlements where today only a few people live, but that didn't seem to make sense. Large settlements meant intensive agriculture, something that was supposed to be impossible, but Erickson's college William Balée has found tantalising clues that long ago the Sirionó were cultivating a variety of important crops.

WILLIAM BALÉE: The Sirionó language has some words for domesticated plants that appear to be derived from a language spoken 2,000 years ago and that was associated with agricultural society.

(TO VILLAGER) How do you say maize?

VILLAGER: Ibazi.

WILLIAM BALÉE: These words include the word for achiote which is a red dye plant.

VILLAGER: (SIRIONÓ WORD FOR ACHIOTE)

WILLIAM BALÉE: It includes the word for cotton.

VILLAGER: (SIRIONÓ WORD FOR COTTON)

WILLIAM BALÉE: They had these words not because they borrowed them from some other people, but because they have retained the cultivation of these plants through time.

NARRATOR: Like the Sirionó today, it seems the people who once lived here were settled farmers. They cultivated colourful dyes, they grew and span cotton for their clothes, they lived on carefully engineered mounds above the savannah's seasonal flood waters and ate staple crops like maize. Unlike with Orellana in the Central Amazon, there's a credible Spanish account of the area. Here Erickson found more evidence of a sophisticated society.

CLARK ERICKSON: The Solis de Holguin expedition came in in 1617 and they described entering these towns on causeways that were, they said they could ride four horses abreast, and as grand as, as the cities in, in Spain and so they were remarkably impressed with these roads, their straightness and the engineering.

NARRATOR: The Spanish account is backed up by hard evidence on the ground. One of these roads is still there.

CLARK ERICKSON: Doesn't look like much, but this is actually a prehistoric causeway that was constructed some time in the past before the arrival of the Spanish and it's still in use today. It's about 10, maybe 15m across and about 2m tall and very well preserved today. You can see the pathway going along it and they would construct these. They took the soil out from one side or both sides of the causeway and in doing so they created a canal to interconnect these areas between the mound.

NARRATOR: Settlements, roads, canals. Just how big was this society on the Mojos Plains? It was time to take to the air. At last it was clear just what the mysterious straight lines were: they were the remains of a vast network of raised roads and canals running between the settlements.

CLARK ERICKSON: So in this forest island in Baures you can see 50-100 causeways radiating out connecting it to other forest islands.

NARRATOR: And the strange striped patterns? These were also prehistoric earthworks, fields deliberately raised up a few feet above the savannah floor. Erickson believes that this was how crops were grown, where agriculture is so difficult today. Raised fields would have stayed dry in the wet season and in the dry season they were surrounded by shallow canals, a source of year-round irrigation.

CLARK ERICKSON: Raised fields are an ingenious way of cultivating areas that have generally poor soils and also very deep water during the rainy season.

NARRATOR: Erickson has found that the remains of the raised fields stretch for thousands of square kilometres. They could have sustained a huge population. Hundreds of thousands, perhaps even a million people could have lived in this remote corner of the Amazon Basin.

CLARK ERICKSON: There are times when I've been flying over this landscape and you look down and we see the beginnings of some of the raised fields. We're going to fly for sometimes 15-20 minutes, continuous engineered landscape, literally from horizon to horizon in some areas. It's truly spectacular the scale and immensity of this transformation.

NARRATOR: Finally it was clear to Erickson just what he was looking at: a society that had totally mastered its environment, a civilisation of builders and engineers as sophisticated as any in the Ancient World.

CLARK ERICKSON: When you look at the amount of labour that went into building these earthworks, the amount of earth moved, person hours involved with altering rivers' courses, building these channels connecting rivers, raising the roadways it's on par with anything the Egyptians did in terms of their pyramids or cities.

NARRATOR: These discoveries in the Bolivian Amazon raised an obvious question: if people here could overcome the limitations of their environment perhaps Orellana's claims were not so outlandish after all. Perhaps there had been an El Dorado all those hundreds of miles away in the Central Amazon and sure enough when scientists began to look more closely at the Indian tribes of the Amazon they found evidence that didn't fit with the idea that these were people who had always been stuck in the Stone Age. A few years ago anthropologist Mike Heckenberger came to work with the Kuikuru, a classic small Amazonian tribe of just 300 people. He assumed he would be dealing with a simple society, but what he found was altogether more puzzling.

MICHAEL HECKENBERGER: There are several aspects of their social structure that are very, very similar to complex or hierarchical societies elsewhere, for instance the existence of chiefly individuals who are fundamentally different at birth than non-chiefly individuals.

NARRATOR: To Heckenberger's surprise, he found that this tiny tribe had a fully-fledged aristocracy. The differences in status were expressed mainly through ritual.

MICHAEL HECKENBERGER: Some of the flutes, for instance, are only used for the commemoration of chiefly individuals.

NARRATOR: It seemed strange. Why should such a tiny group have such a complex hierarchy, but then Heckenberger found signs that the Kuikuru had once been very different. Near to the present-day village he unearthed the remains of a prehistoric settlement.

MICHAEL HECKENBERGER: How's it going guys?

NARRATOR: What was significant was its size.

MICHAEL HECKENBERGER: The plaza was more or less the size of a contemporary village, but the residential areas surrounding it were significantly larger, well over ten times the size of a contemporary village.

NARRATOR: The prehistoric village would have dwarfed the present-day one and what's more, just as in the Bolivian Amazon, this large village was one of many.

MICHAEL HECKENBERGER: Where today there's one village, in the past in prehistoric times this village was integrated with other villages as close as three or four kilometres away.

NARRATOR: It all suggests that the prehistoric Kuikuru were not a tribe of Stone Age semi-nomads caught at the dawn of time. Instead they, and perhaps other Central Amazonian tribes, had once lived in large, settled societies, exactly the sort of societies described by Orellana. So archaeologists have recently begun again to explore the rainforest Orellana travelled searching for his lost civilisation and as he explored Brazil's Tapajos river, Bill Woods identified a subtle but important clue.

PROF WILLIAM WOODS (Southern Illinois University): It's, it's somewhat difficult to see, but near the top of this low bluff along the Tapajos we have very dark soil. This is just a very good example of what covers tens of thousands of hectares in the local region.

NARRATOR: This black soil, or terra preta as the Brazilians call it, is dotted all over the Amazon jungle, but what intrigued archaeologists is what it contains.

JAMES PETERSEN: You'll see all kinds of things scattered over the ground here. Many of them look like rocks or stones, but in fact they're all artefacts, mostly pottery sherds, busted up jars made by the Indians one to two thousand years ago. It's a, it's a, it's a very dense concentration, rather remarkable in all senses. After just a minute or two I was able to pick up several handfuls of really dramatic pottery sherds. if we can imagine what the whole jars would look like we'd be rather surprised by these fine works of art.

NARRATOR: The pottery they have found is exquisite and much of it dates from the time of Christ, long before the coming of the Europeans. It was the first hard proof that there had once been an advanced culture in the heart of the rainforest and when they dug down into the terra preta scientists made the most revealing discovery of all. Not only was the black soil full of pottery, but it was almost exactly the same composition as the yellow jungle soil around it, except it had been mixed with organic waste. That meant the terra preta had to be man-made.

DR EDUARDO NEVES (University of Sã';o Paulo): We know that, that this terra preta here formed with the soil, so they look very different and they are very different in a way, but that's the matrix for that. We have to have human action interfering in the yellow soil in order to create the terra preta.

NARRATOR: It was the key revelation. It meant that wherever you find terra preta there people had once lived, so scientists have started mapping the black soil and wherever Orellana reported seeing settlements there they have found it. All along the banks of the Amazon, up the Rio Negro and down the Tapajos they are finding the terra preta. In all, a massive area, twice the size of Britain.

JAMES PETERSEN: Some have estimated perhaps that as much as 10% of Amazonia's covered with this Amazonian dark earth or terra preta. Its widespread distribution if linked to culture, which the vast majority of contemporary scientists believe, suggests that native cultures are not only widespread but in some cases phenomenally numerous.

NARRATOR: But to convince everyone that there really had been a large prehistoric population in the Central Amazon the archaeologists still had to explain how these people had achieved what we cannot. How had they fed themselves on the poor Amazonian soil? The answer again seems to lie in the terra preta.

ADILSON De S SANTOS: The soil is easy to work and very fertile. We plant papaya, we plant banana, corn, beans and manioc in terra preta. Whatever you plant in terra preta does exceptionally well.

NARRATOR: Terra preta is so fertile that it's been prized by Brazilian farmers for centuries. Somehow the prehistoric Amazonians had transformed the world's worst soil into some of the best.

JAMES PETERSEN: Unintentionally perhaps, maybe intentionally, the native people enriched the soil in and around where they lived and this turn enabled them to intensify their agriculture which then, in turn, enabled their numbers to grow and become complex and Orellana and the things he described become more than plausible, very likely in this scenario.

NARRATOR: So here is the truth behind the myth of El Dorado. The prehistoric people of the central Amazon transformed the very earth beneath their feet. From their black soil sprang a civilisation that lasted for over one thousand years. They fashioned works of art to rival those of the Mayas and Incas. They built towns and even cities that spread across the jungle. Eventually they settled the Amazon Basin with millions and millions of people. It seems Orellana was telling the truth after all, but if there really had been a great society here, what had become of it? How could it have disappeared so suddenly and so completely? The most likely answer is tragically simple.

DR CHARLES CLEMENT (Institute for the Study of the Amazon): When the Europeans arrived here they found a population with a lot of susceptibility to disease and so disease took off like a wildfire in dry straw and over two hundred years the population just crashed.

NARRATOR: Smallpox, influenza, measles - these were the agents of the rapid and complete destruction of Amazonian civilisation. Orellana was both the first and last European to set eyes on it. The disease which followed in his wake destroyed in a few decades what had taken centuries to create and so a people who once dominated this landscape disappeared almost without leaving a trace. Today the jungle has reclaimed the places where there used to be towns and cities, but that is not the end of their story. There is one final twist to this tale and it's to do with the Indians' mysterious black earth. Today the Amazon rainforest is under threat as never before. Millions of acres have been wiped out every year as farmers slash and burn their way across the jungle in a largely futile attempt to turn it into farmland. The problem is once the forest has been cleared the rain just washes all the goodness out of the soil. Often, after just a few years, the farmers have to move on leaving only wasteland behind. It's one of the great environmental disasters, but now scientists have started to wonder. If millions of prehistoric Indians once lived sustainably in the Amazon then perhaps we can learn from them. What is the secret of the terra preta? Why is it so fertile year after year? There may be a clue in Orellana's account of that first journey down the Amazon.

READER: We entered the dominion of Aparia on St John's Day and already the Indians were beginning to burn over their fields.

NARRATOR: If Orellana's observation is accurate then the Indians were using fire, but clearly not in our slash and burn fashion. Detailed analysis of the terra preta has shown it to be full of burnt plant material, but in a special form: charcoal.

DR JOHANNES LEHMANN (Cornell University): charcoal is in the area here made largely with earthen kilns where organic material, like these logs, are piled up and earth mounds are built around them and under partial exclusion of oxygen you get this charcoal.

NARRATOR: Charcoal is made when you only partially burn the trees and plants. This makes it different to slash and burn where the plant life and all the nutrients it contains are completely reduced to ash. This can be swiftly washed away by the rain, but charcoal can last in the soil for hundreds of years.

JOHANNES LEHMANN: So one of the hypothesis is that the Amerindian populations actually used some sort of slash and char technique as a soil fertility enhancer.

NARRATOR: Inspired by the Ancient Amazonians, Johannes Lehmann's student, Christoph Steiner, decided to find out exactly what effect ancient slash and char methods could have, so he has planted a series of experimental plots, some with added charcoal, some without. The experiment is still not finished, but already the results have been amazing.

CHRISTOPH STEINER (University of Bayreuth): On this plot we see what happens if we follow the traditional slash and burn technique. After the first harvest already there's nothing growing anymore and we have here now the third harvest. Here on this plot we applied mineral fertiliser, but that is not very satisfying. If you look on this there's almost no yield, almost no grain: a family couldn't live on this. That is not satisfying yield. In comparison though a plot where we, where we applied additional charcoal. Here we can see that the yield is much bigger, so there is corn and this is a plot where we applied charcoal and mineral fertiliser and this combination last harvest we had an increase in crop production of 880% in comparison to mineral fertiliser without charcoal.

NARRATOR: An 880% increase in yield is almost miraculous. Charcoal seems to hold the nutrients in the soil preventing them from being washed away by the trains. It's a simple trick, but one that Steiner believes could be the key to breaking the destructive cycle of slash and burn and so reduce the pressure on the rain forest.

CHRISTOPH STEINER: Increased soil fertility means bigger crop production and people can use the same piece of land for more time for more crop production, don't, are not forced to clear a new piece of primary intact tropical rainforest.

NARRATOR: And scientists now believe that terra preta holds yet one more secret. It seems to have another unique property, something that may once have helped it to spread across the Amazon and could now help it to spread across the world. The discovery has been made by Bill Woods. A few years ago he came across a place where terra preta was being mined and then sold on to local gardeners.

WILLIAM WOODS: What we have here is a material that is so valuable that, that people are coming in trucks and buying it. Absolutely unexpected.

NARRATOR: With decent soil so scarce in the Amazon, selling the terra preta seems an odd thing for a farmer to do, but here they've been doing it for 20 years because it appears that the black earth just keeps growing back.

FARMER: After digging the soil that's left will grow deeper. It's because it's being fed by the leaves that fall on it. You can see it happening over there and in there now.

WILLIAM WOODS: The situation is he mines it, he leaves 20cm, he allows it to rest. Then after a 20 year period the depth of this dark soil is the same as it was before the mining operation. This is extremely important in that it strongly suggests that the material is alive and that the biology of this material is the important thing that we're looking at.

NARRATOR: If Woods is right the terra preta can, in some mysterious way, reproduce itself just like a living thing. Scientists are now working to find out how it does it. There are literally tens of thousands of species of bacteria and fungi in the soil and they suspect that somewhere among them must be unique micro-organisms that allow the terra preta to grow. The hope is that if they can unlock its secrets we could reproduce terra preta anywhere. Then we

could boost food production throughout the developing world. We could bring a halt to slash and burn. It sounds too good to be true, but the Indians' black earth could one day help to feed the world and save the rainforest.

WILLIAM WOODS: Here now we have, we have people that, that really have problems feeding themselves and so if then we can understand the legacy of, of the terra preta I think really that, that's our El Dorado. This would be important for the world.

NARRATOR: So there is a true irony to the story of the hunt for El Dorado. There was once a great civilisation in the Amazon, one the Europeans destroyed even as they discovered it, but the Amazonians may have left us a legacy far more precious than the gold the Conquistadors were seeking. That black earth, the terra preta, may mean a better future for us all.

AGRICULTURE:The Real Dirt on Rainforest Fertility

Ancient Amazonians left behind widespread deposits of rich, dark soil, say archaeologists. Reviving their techniques could help today's rainforest farmers better manage their land

IRANDUBA, AMAZÔNAS STATE, BRAZIL--Above a pit dug by a team of archaeologists here is a papaya orchard filled with unusually vigorous trees bearing great clusters of plump green fruit. Below the surface lies a different sort of bounty: hundreds, perhaps thousands, of burial urns and millions of pieces of broken ceramics, all from an almost unknown people who flourished here before the conquistadors. But surprisingly, what might be most important about this central Amazonian site is not the vibrant orchard or the extraordinary outpouring of ceramics but the dirt under the trees and around the ceramics. A rich, black soil known locally as terra preta do Indio (Indian dark earth), it sustained large settlements on these lands for 2 millennia, according to the Brazilian-American archaeological team working here (see sidebar).

Throughout Amazonia, farmers prize terra preta for its great productivity--some farmers have worked it for years with minimal fertilization. Such long-lasting fertility is an anomaly in the tropics. Despite the exuberant growth of rainforests, their red and yellow soils are notoriously poor: weathered, highly acidic, and low in organic matter and essential nutrients. In these oxisols, as they are known, most carbon and nutrients are stored not in the soil, as in temperate regions, but in the vegetation that covers it. When loggers, ranchers, or farmers clear the vegetation, the intense sun and rain quickly decompose the remaining organic matter in the soil, making the land almost incapable of sustaining life--one reason ecologists frequently refer to the tropical forest as a "wet desert."

Because terra preta is subject to the same punishing conditions as the surrounding oxisols, "its existence is very surprising," says Bruno Glaser, a chemist at the Institute of Soil Science and Soil Geography at the University of Bayreuth, Germany. "If you read the textbooks, it shouldn't be there." Yet according to William I. Woods, a geographer at Southern Illinois University, Edwardsville, terra preta might cover as much as 10% of Amazonia, an area the size of France. More remarkable still, terra preta appears to be the product of intensive habitation by precontact Amerindian populations. "They practiced agriculture here for centuries," Glaser says. "But instead of destroying the soil, they improved it--and that is something we don't know how to do today."

In the past few years, a small but growing group of rsearchers--geographers, archaeologists, soil scientists, ecologists, and anthropologists--has been investigating this "gift from the past," as terra preta is called by one member of the Iranduba team, James B. Petersen of the University of Vermont, Burlington. By understanding how indigenous groups created Amazonian dark earths, these researchers hope, today's scientists might be able to transform some of the region's oxisols into new terra preta. Indeed, experimental programs to produce "terra preta nova" have already begun.

The research is still in an early stage, but last month attendees at the first large-scale scientific congress* devoted to terra preta argued that its consequences could be enormous, both for Amazonia and for the world's hot regions in general. Population pressure and government policies are causing rapid deforestation in the tropics, and poor tropical soils make much of the clearing as economically nonviable in the long run as it is ecologically damaging. The existence of terra preta, says Wim Sombroek, former director of the International Soil Reference and Information Center in Wageningen, the Netherlands, suggests "that some kind of sustainable, intensive agriculture is possible in the Amazon, after all. If we can learn the principles behind it, we may be able to make a substantial contribution to human welfare and the environment."

The good earth

Terra preta is scattered throughout Amazonia, but it is most frequently found on low hills overlooking rivers--the kind of terrain on which indigenous groups preferred to live. According to Eduardo Neves, an archaeologist at the University of São Paulo who is part of the Iranduba team, the oldest deposits date back more than 2000 years and occur in the lower and central Amazon; terra preta then appeared to spread to cultures upriver. By A.D. 500 to 1000, he says, "it appeared in almost every part of the Amazon Basin."

Typically, black-soil regions cover 1 to 5 ha, but some encompass 300 ha or more. The black soils are generally 40 to 60 cm deep but can reach more than 2 m. Almost always they are full of broken ceramics. Although they were created centuries ago--probably for agriculture, researchers such as Woods believe--patches of terra preta are still among the most desirable land in the Amazon. Indeed, terra preta is valuable enough that locals sell it as potting soil. To the consternation of archaeologists, long planters full of terra preta, complete with pieces of pre-Columbian pottery, greet visitors to the airport in the lower Amazon town of Santarém.

As a rule, terra preta has more "plant-available" phosphorus, calcium, sulfur, and nitrogen than surrounding oxisols; it also has much more organic matter, retains moisture and nutrients better, and is not rapidly exhausted by agricultural use when managed well.

The key to terra preta's long-term fertility, Glaser says, is charcoal: Terra preta contains up to 70 times as much as adjacent oxisols. "The charcoal prevents organic matter from being rapidly mineralized," Glaser says. "Over time, it partly oxidizes, which keeps providing sites for nutrients to bind to." But simply mixing charcoal into the ground is not enough to create terra preta. Because charcoal contains few nutrients, Glaser says, "high nutrient inputs via excrement and waste such as turtle, fish, and animal bones were necessary." Special soil microorganisms are also likely to play a role in its persistent fertility, in the view of Janice Thies, a soil ecologist who is part of a Cornell University team studying terra preta. "There are indications that microbial biomass is higher in terra preta," she says, which raises the possibility that scientists might be able to create a "package" of charcoal, nutrients, and microfauna that could be used to transform oxisols into terra preta.

Slash-and-char

Surprisingly, terra preta seems not to have been created by the "slash-and-burn" agriculture famously practiced in the tropics. In slash-and-burn, farmers clear and then burn their fields, using the ash to flush enough nutrients into the soil to support crops for a few years; when productivity declines, they move on to the next patch of forest. But Glaser, Woods, and other researchers believe that the long-ago Amazonians created terra preta by a process that Christoph Steiner, a University of Bayreuth soil scientist, has dubbed "slash-and-char." Instead of completely burning organic matter to ash, in this view, ancient farmers burned it only incompletely, creating charcoal, then stirred the charcoal directly into the soil. Later they added nutrients and, in a process analogous to adding sourdough starter to bread, possibly soil previously enriched with microorganisms. (In addition to its potential benefits to the soil, slash-and-char releases much less carbon into the air than slash-and-burn, which has potential implications for climate change.)

In a preliminary test run at creating terra preta, Steiner, Wenceslau Teixeira of the Brazilian Agricultural Research Enterprise, and Wolfang Zech of the University of Bayreuth applied a variety of treatments involving charcoal and fertilizers to test plots of highly weathered soil at a site outside the central Amazonian city of Manaus. They then planted rice and sorghum in each plot for 3 years. In the first year, there was little difference among the treatments (except for the control plots, in which almost nothing grew). But by the second year, Steiner says, "the charcoal was really making a difference." Plots with charcoal alone grew little, but those treated with a combination of charcoal and fertilizer yielded as much as 880% more than plots with fertilizer alone.

The "Bambi syndrome"

Researchers believe the best use of the newly revived technique will be in a kind of updated version of precontact indigenous agriculture, which used methods very different from slash-and-burn. According to a pathbreaking 1992 analysis by William Denevan, a geographer emeritus at the University of Wisconsin, Madison, the slash-and-burn agriculture practiced until recently by most Amazonian cultures is probably a recent invention. In contemporary slash-and-burn, farmers shift from plot to plot every 2 to 4 years. But field experiments by archaeologists in Amazonia indicated that clearing the forest with stone tools was so difficult that rapid movement among areas would have been impractical, if not impossible. "What they found was that for a single moderate to big hardwood tree it can take more than 30 times longer to cut down that tree with a stone ax than with a steel ax," Denevan says. "I

argued that this meant that Indians had to stay with a piece of land in precontact times for much longer than they do now and had substantially different agricultural regimes."

Rather than planting annual crops, the precontact inhabitants of the Amazon mostly practiced a type of agroforestry, argues Charles R. Clement, a plant geneticist at the Brazilian National Institute for Amazonian Research in Manaus. Initial paleoecological analyses of charred plant remains from the Iranduba archaeological site show, in addition to annual crops such as manioc and maize, the wood from at least 30 species of useful trees. "They put down annuals until the orchards grew," suggests Clement. "We'll have to find some modern equivalent to Indian agroforestry. Otherwise creating new terra preta"--if scientists learn how to do it--"will simply lead to the same kind of clearing we have now, except the land will last longer." Indeed, research in Amazonia by Laura German of the International Center for Research in Agroforestry in Nairobi, Kenya, has shown that over time the nutrients in terra preta, when poorly managed, can decline to near-oxisol levels.

New terra preta farms, researchers acknowledge, will be subject to novel problems, especially weeds. In small central Amazon plots, German says, weeds grow so fiercely on terra preta that they overwhelm crops--they are a principal reason that farmers on ancient terra preta sites move their fields. New techniques to control tropical weeds will have to be developed, says Cornell weed scientist Antonio DiTommaso, much as scientists have created methods to manage temperate-zone weeds.

Some researchers hope that the more intensive agroforestry possible on terra preta would allow landowners to spare more tropical forest, especially near cities like Manaus, where the organic waste now overflowing dumps could be burned to provide charcoal. It might even be possible to reclaim cleared land. But because the benefit of increased yields depends on quickly transporting produce and fruit to large markets, the increased costs of terra preta may not be economically viable in remote parts of Amazonia. In addition, Clement argues that any success with terra preta will simply lure more people to work with it and that those people will end up clearing forest in the process. "Terra preta is about making the current process of development more rational and sustainable, not about conservation," he says. "It's about creating the conditions for the forest to return more quickly after it's cleared, not about preserving it from development."

Even if Clement's view is correct, examining terra preta is still worthwhile, according to Susanna Hecht, a geographer at the University of California, Los Angeles. "We have to get over this Bambi syndrome of seeing all development in the tropics as necessarily catastrophic," she says. "People have been farming there--farming hard--for thousands of years. We just have to learn how to do it as well as they did."

Archaeologist helps bring old techniques to life

Esaúl Sánchez, Compass reporter

"The most dramatic thing about this land is its seasonal changes," says Dr. Clark Erickson, referring to Llanos de Mojos, the impoverished region in Bolivia where he leads his archaeological digs. "For four or five months a year, the land is flooded. Then it dries out."

The research that Erickson, associate professor of anthropology at Penn, has conducted in the region has scholarly value - but he hopes that it will have practical results as well.

During the wet season, he says, Llanos de Mojos "is almost an aquatic world, similar to the Everglades in Florida. It has green grass, swamps, and patches of green trees popping up here and there. Many roadways are closed, so people get around by canoes or airplanes. Then comes the dry season. As the land dries, the grassland turns into shades of brown and yellow."

Llanos de Mojos is a flat landscape in the lower Andes. The unvarying flatness is interrupted by small, dense jungles near the riverbanks. The indigenous people of these forests hunt and practice "slash-and-burn" agriculture for their subsistence. Cattle ranchers live in the flat savannas.

Llanos de Mojos, says Erickson, has been a poor region for centuries. Yet there was a time when it was not. By studying aerial and satellite photographs and the results of archaeological digs, researchers like Erickson have discovered thousands of rectangular "islands" built about twenty centuries ago by the ancestors of today's Mojos

Indians. The farmers grew root vegetables, a strong caffeine-based tea plant, achiote (used as a red paint), and perhaps corn on these islands, which produced enough crops to feed a large population.

According to William Denevan, who first found these pre-Columbian earthworks, this region was sustaining at least 200,000 inhabitants five centuries ago. Now, most of the people in the region live in cities, not on the land.

Making use of the region's climateFor 15 centuries, the Mojos Indians cultivated these plains by using a farming technique that exploited the region's climate. During the dry season, they would divide the land into rectangles 10 feet wide and ranging from 100 feet to one-quarter of a mile long. Rectangles were laid out 10 feet apart from each other. Then the Indians would excavate the area between the fields some three or four feet deep. The soil that was removed was deposited on top of the rectangular fields. When the rainy season came, the depressions would become canals and the raised fields would be about one foot above the water level, allowing for normal agriculture in spite of the flooding.

To maintain the best level of water, the Indians built dikes and flood gates, which allowed them to extend the growing season by conserving moisture. Next to the fields, they built larger canals for transporting goods in canoes. The arrival of the Spanish and with them diseases previously unknown in the Americas put an end to these gardens that were spread over an area the size of Pennsylvania. The diseases killed most of the region's Indians-and their farming techniques perished with them.

Until now. Erickson and other archaeologists working in the raised fields began to wonder whether this old farming technique could be used to help develop the economy of this impoverished region.

Erickson, who teaches "Fundamentals of Archaeology," "Andean Archaeology," and "Archaeology of Complex Societies" at Penn, spends his summers in Bolivia (its dry season). He has published and delivered several papers about the region, including one earlier this spring at the meeting of the Latin American Studies Association in Atlanta.

Through projects that attempt to duplicate what the Mojos Indians used to do, he has concluded that, even by modern standards, the ancient agricultural technique is impressive. During the rainy season, the canals drain excess water, while dikes and dams store water for the dry season. Algae and aquatic plants in the canals and the organic matter deposited at the bottom can be used to fertilize the fields. In addition, the canals can be used to collect and harvest fish.

"It would be very naive to think that these technologies can be put back into use very easily and everyone will be happy," says Erickson. "There have been major climatic, social, and economic changes since these systems were last used. Rehabilitating ancient technologies requires intensive study followed by small-scale pilot experimentation."

Rewriting an "instruction manual"Nevertheless, from simply studying the distant past, Erickson now has accepted the challenge of rewriting a kind of lost instruction manual for agricultural practices. In 1990, Erickson and associates from the local Bolivian university built about a dozen small raised fields in an acre of flooded savanna. This experimental plot eventually produced more corn than traditional fields of comparable size in the forests. The station also produced cassava, a starchy root crop not cultivated in the savannas.

After the success of that small experiment, Erickson and colleagues started taking his results to local communities. At a typical meeting, he explains, "We discuss raised fields for two hours. They are usually very interested, and they have all sorts of concerns about the labor and time involved, where the raised fields could be built, what they are going to get out of it." Since the project is experimental, he adds, "we use incentives. We spend a lot of time discussing what an experiment is, that it might fail or it might not, and in the end it is theirs to run." The arrangement is for the diggers and the data-collectors to receive a daily salary and meals. "In the end," says Erickson, "they get the harvest and we get the data."

There is not much labor available in Llanos de Mojos to build the fields. Many of the communities are small and dispersed. Erickson keeps looking for further ties with local people, organizations, universities, and development organizations to expand the use and testing of this rediscovered way of making the region productive.

From his perspective, using ancient knowledge to develop a region's economy is the most exciting part of his archaeological work. He says he is committed to work in Bolivia for a long time - "maybe," he adds, "for the rest of my life."

Erickson has written a chapter on his current research for Archaeology in the American Tropics: Current Analytical Methods and Applications, to be published later this year by Cambridge University Press.

Reconstructing the past of Llanos de Mojos"Most of my colleagues believe that tropical forests are bad places to do archaeology because nothing is preserved," says Dr. Clark Erickson.

To help fill the gaps in the archaeological record of Llanos de Mojos, Erickson uses data from the experimental plots he is helping to build on the Bolivian savanna. The participating farmers receive technical orientation, salaries, and meals - and the harvest is theirs to keep. In return, the farmers and Erickson keep track of the agricultural yields of each plot and how much labor was required to make the system work.

Erickson then makes informed guesses about the number of people that might have lived in Llanos de Mojos before the arrival of the Spanish. He is trying to determine the number of people that were needed to work the fields, how they were organized, and how self-sufficient the system was - how, in effect, the people lived. In the meantime, Erickson keeps an eye open for any pottery and other hard clues that may shed light on the culture and beliefs of the Mojos Indians.

Although the neighbors to the west of the Mojos Indians were the powerful Incas, the Mojos remained independent of them. According to Erickson, "The Mojos were a separate, parallel culture."

Another question archaeologists like Erickson would like to answer is how the Mojos Indians learned the farming technique of the raised fields. Ancient raised fields have been found in Africa, China, New Guinea, Mexico, and Belize-as well as in South Florida, Michigan, and Wisconsin. -Esaúl Sánchez

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Ari Siiriäinen & Martti Pärssinen

Eighty years after Erland Nordenskiöld: The question of the eastern frontier of the Inca Empire in Bolivia

This article is based on a paper presented in the conference "Past and Present in Andean Prehistory and Early History" in Gothenburg, Sweden, 16-17. September 1996. It will be published in the forthcoming conference proceedings.

The Swedish archaeologist and anthropologist Erland Nordenskiöld (1877-1932), son of the famous polar explorer Adolf Erik Nordenskiöld, dedicated his whole career to the investigations of South American prehistory and ethnography. He was working in both the highlands and lowlands of northern Argentina, Bolivia and southern Peru. Thus, one of his main explicite interests was to study the relationships of the highland and lowland cultures in a historical perspective and the marginal cultures of the highland sphere in general.

In the late winter months of 1913 Nordenskiöld was leading his small exploration party, consisting of himself, his wife Olga, two Swedish companions and an Argentinian assistant, riding their mules towards the small town of Lagunillas in the eastern foothills of the Bolivian Andes. Before they arrived to Lagunillas, some 20 km or so still to ride, they heard from the local people that not far from the track there are forgotten ruins of an Inca fortress hidden behind thick vegetation. They eventually discovered the fortress, and within the few days the party spent there, Nordenskiöld, being a clever cartographer, had scetched an excellent map over the site and made limited test excavations there. (Nordenskiöld 1915)

The local people called the site Inkahuasi, the house of the Inca, which emphasized the historical importance of the fortress. Nordenskiöld concluded very soon that it could not be anything else than the fortress of Cuzcotuyo of the historical documents. This site was mentioned, among others, by Sarmiento de Gamboa in his well-known chronicle "Historia general llamada Indica" from 1572 and Bernabé Cobo in his "Historia del Nuevo Mundo" from 1653.

Since Nordenskiöld's visit to Inkahuasi and his idenfication of the fortress no-one has dedicated any scholary thoughts to this issue, only a few passing references have been made by historians - one of them is Thierry Saignes, who published a map in his history of the eastern Andes, "Los Andes orientales: historia de un olvido" from 1985. On this map (Saignes 1985: 30) he marks Cuzcotuyo, or Cuscotoro, as it was also mentioned in the historical documents, west of Nordenskiöld's Inkahuasi. Unfortunately, Saignes does not touch the question in his text and thus it remains unknown from where he got the idea of deviating from Nordenskiöld's identification by making a clear difference between Cuzcotuyo and Inkahuasi. But confusingly, in a couple of pages earlier Saignes (1985: 26) explicitly states that Cuzcotoro is precisely the same fortress as Nordenskiöld's Inkahuasi.

There are also other propositions as to which one of the already known fortresses could be identified as Cuzcotoro. For example, John Hyslop (1990: 176) and Teresa Gisbert de Mesa (1988: 85) suggest that Inkallacta, a large fortress also first described by Erland Nordenskiöld during his Bolivia expedition in 1913-14 and situated c. 250 km northwest of Inkahuasi, could be Cuzcotoro; we consider this, however, unlikely (cf. Pärssinen 1992: 130). Recently Vincent Lee, an architect and amateur archaeologist, located a simple circular wall called Inkapirca on the top of a mountain c. 60 km NW of Inkahuasi suggesting for his part that this could be the Cuzcotoro of the chronicles (Lee 1992). - Thus, at least three different archaeologically known fortress sites have had the honour to be the candidate for this enigmatic fort of the historical sources.

This question in mind we journeyed to the area in August 1993, exactly 80 years after Nordenskiöld and his small party. After a few weeks' search we managed to locate a fortress on the top of Serranía Khosko Toro exactly 50 km to the northwest of Inkahuasi. The site had been visited also by Vincent Lee in 1991 (Lee 1992), but we had no information about this in our disposal when we were exploring the area. However, Lee, being a layman in archaeology, was not able to identify correctly the fortress he discovered (cf. above).

As a comprehensive primary description of the site will be published later together with all the evidence which led us to the top of Serranía Khosko Toro (Pärssinen & Siiriäinen, forthcoming), we only refer here to Figs. X and X in which the general layout of the site and the plan of the main building are given. The large rectangular buildings are obviously kallankas (soldiers' barracks) and the small circular stone settings foundations of kollkas (silos for crops).

We have substancial archaeological, historical and onomastic evidence, which will be discussed in detail in the above-mentioned article, to argue that the fortress on Serranía Khosko Toro is the real Cuzcotoro of the documents, not Nordenskiöld's Inkahuasi nor Inkallakta or Lee's Inkapirca. But if the fortress on Serranía Khosko Toro really is, as we now believe, Cuzcotoro, what is then the correct identification of the fortress found by Erland Nordenskiöld on Serranía Incahuasi? Now we have to turn to certain archive material. Tierry Saignes located, in the Archivo General de Indios in Seville, an inauguration letter to a certain don Francisco Aymoro for the governorship of the Yamparaes area of the Charcas province from 1586; in this letter it is stated that there are in Yamparaes three Inca fortresses, namely one in Dilava, one in Conyma and a third one in Cuzcotoro. Even some other similar documents speak of these same three garrisons (cf. Pärssinen 1992: 124). This means that Inkahuasi must be either Conyma or Dilava - but there should also be a third fortress somewhere on the same mountain ridges. While we were climbing on the slopes of Serranía Khosko Toro, our guide very casually mentioned that in fact he knew another Inca ruin on Serranía Iñao half-way between Khosko Toro and Inkahuasi. Next year, in summer 1994, one of us (MP) took a rough bearing from Khosko Toro to Inkahuasi and could indeed locate a fortress on Serranía Iñao with the help of local campesinos who knew the area well. At this site there were several quite small rectangular buildings plus one larger one, probably a kallanka, and in addition straight walls and three agricultural terraces, but no kollkas. Obviously this site represents a garrison for a smaller military contingent with more occasional or short term occupation than that in Cuzcotoro. Anyhow, even here the stone constructions and the overall plan of the site indicate Inca architecture, and a few potsherds sampled from the site resemble true Inca pottery although with less certainty than in Cuzcotoro, where we found Inca pottery from a testpit we excavated into one of the rooms of the main building.

Thus, we have a chain of three fortresses in our area roughly on a straight line perpendicular to the frontier zone. At this stage it is impossible to say if this is a repeating pattern or not, but this issue is certainly worth investigating even in other sections of the eastern frontier. For instance, west of Lake Titicaca the sites of Iskanwaya and Ixiamas, where the Bolivian archaeologist Juan Faldín (personal communication and a report in the archives of Instituto Nacional de Arqueología Boliviano, La Paz) has located a fortress, might have a third companion fortress somewhere in between. Of course these perpendicular chains of garrisons might consist of only two sites or even more than three. The chains could either reflect a defence system in depth against the plains Indians thus indicating the real breadth of the frontier zone, or they could equally well reflect a process of penetration of the Inca control into the territory of the plains Indians. In the former case the fortresses would have been occupied simultaneously, and in the latter case they would have been built successively as the Inca control extended farther and farther to the east.

The real function, or functions, of the sites is not either precisely known so far. That they were military posts and had a defence function, seems obvious (defensive walls and topographic locations, the presence of kallankas). But as the highlanders had also peaceful contacts with the plains Indians trading metal for coca, wood, wax, honey and exotic birds, these fortifications served probably as trading outposts and strongholds as well - this might explain the Chiriguano pottery we discovered in a testpit we excavated to the main building in Cuzcotoro. In any case, the fortresses were certainly multiethnic communities into which the Incas sent altiplano people as mitimaes and mercenary troops under the leadership of noble Cuzco Indians or "orejones".

Typical for the Inca policy was to continue penetrating as far east as possible for more trading contacts or in order to protect the highland communities behind a frontier zone as broad as possible. This also means that, because of the hostile attacks of the plains Indians and in Bolivia especially of the Chiriguanos and other Chaco tribes, the frontier zone was in a constant process of movement back and forth in an east-west direction.

One of us (MP; Pärssinen 1992) has gone through most of the historical documents in which the activities of the Incas towards the east are related, and he has also critically evaluated some of the conclusions made by historians on the basis of documents. Concerning the frontier zone in northern Bolivia, i.e. east of Lake Titicaca, he is of the opinion, although no direct confirmation in the Inca sources or written documents exists, that expeditions sent by Topa Inca reached the confluence of the Madre de Dios and Beni rivers (Pärssinen 1992: 112). A quipu based text of the descendants of Topa Inca, initially edited and published by John Rowe (Capac Ayllu [1596] 1985, Rowe 1985), tells about an expedition to the land of the Yscayssingas (Iscaycingas) via the province of Paucarmayo. One of us (MP), modifying Rowe's interpretation in certain points, concludes that the land of the Yscayssingas was the ultimate point reached by the expedition and that Paucarmayo is a tributary of the river Paitite. The Paitite (or Paititi), when it refers to a river, is according to the comprehensive document of José Alvarez Maldonado, published by Maurtua (1906), the present river Mamoré. Thus, the expedition sent by Topa Inca reached the Mamoré.

We can further refer to an information by the 17th century Guaranís, related by Vasco de Solís (1635) and also published by Victor Maurtua (1906), that the Incas had a settlement "at the point of the Cordilleras" near the confluence of the Madre de Dios, Beni and Mamoré rivers (Pärssinen 1992: 113). The "Cordilleras" mentioned in the text could well be the Serra dos Parecis range, the northwestern edge of which comes to the eastern vicinity of the confluence.

The expedition by Topa Inca, like other expeditions sent by the Inca, followed the course through Camata east of Lake Titicaca towards the upper Beni and thence along this river downstreams, and not a direct route along the Madre de Dios due to the difficult river stretches and fierce tribes there (Saignes 1985: 17, Pärssinen 1992: 111). This information, obtained from the historical sources, seems indeed to fit well to the scanty archaeological evidence we have so-far. William Denevan (1966: 22-23) reports possible Inca constructions on the Beni: ruins and mounds ca. 100 km north of Rurrenabaque on the east side of the river (cf. del Castillo 1929) and another ruin and earthworks in Las Piedras opposite Riberalta, i.e. on the west side of the river near the confluence of the Beni and Madre de Dios. Although attributing these sites to the Incas remains highly uncertain, they are nevertheless worth examining with this possibility in mind; in fact José Chávez Suárez, who has visited the Las Piedras site, reports about potsherds discovered there and says they resemble ceramics in Peru (Chávez Suárez 1944: 42).

Further south, not much is known about the Inca penetration onto the Mojos savannas. It is possible that the relatively dense population, which the extensive field systems of Llanos de Mojos bear witness to (Denevan 1966), and the difficult terrain with annual inundations did not encourage the Inca troops or traders to venture very far towards the lowlands. Possibly the trading and exchange activities which might have been going on within that section of the frontier zone took place closer to the Andean piedmont and the yungas. Perhaps the Mojos Indians did not form such a threat to the highlanders that any forts or garrisons would have been necessary to maintain peace and order - perhaps the Mojos inhabitants, living in an area with fairly reliable floods and secure crops, did not experience such economic catastrophes that would have forced them to attack the highland communities. Thus there was no need to protect the interests of the highlanders with a broad control zone as was the case further north.

However, to the south of the Llanos de Mojos the situation was different. There, in the northern parts of the Gran Chaco plains, lived the Chiriguanos, a fierce tribe of the Tupi-Guaraní cluster which posed a real and constant threat to the highland Indians (see Metraux 1948, Calzavarini 1980). There the Inca penetration was again more aggressive. The easternmost fortresses in this sector are Samaipata, possibly originally already from the pre-Inca period (cf. Boero Rojo and Rivera Sundt 1979), and Inkahuasi, established by Topa Inca towards the end of the 15th century or close to the year 1500 (Saignes 1985: 19); Topa Inca also conquered fortresses built earlier by the local señoríos such as Oroncota (Huruncuta) on the Pilcomayo. However, Guacane, a relative of Huayna Capac, ventured furhter east onto the lowlands of Llanos de Guapay (around the recent town of Santa Cruz de la Sierra) governed by

chief Grigotá and established fortrersses - trading posts? - there, one of them to Huanacopampa (Saignes 1985: 20). The sources clearly indicate that the Incas were in the lowlands not as real conquerors but basing their control on gifts and "flattering" rather than on direct force.

It is not known with certainty how far to the east the Incas penetrated or extended their control. After analysing several sources, one comes to the conclusion that the outermost limit of the Inca control was as far east as on the Brazilian side of the present border between Bolivia and Brazil (Pärssinen 1992: 134). A border document from 1638 by Joan de Lizarazu, published by Maurtua (1906), tells us that "orejones", most probably local Chicha chiefs from the western Chaco whom the Incas had incorporated into their vasallic allies, had villages ("pueblos de los orexones") near Itatin. This Itatin is marked on a map ("Mapa del Rio de la Plata") from ca. 1600 onto the western shore of Rio Paraguay south of the villages of "Xaray". Xaray, in turn, is a swampy region on the Brazilian side of Río Curiche Grande (in Pantanal of Mato Grosso), and even later maps confirm this location of the villages of the "orejones" (cf. Pärssinen 1992: 134).

These documents give us a fairly clear picture of the real breadth and complexity of the frontier region of the Inca Empire against its eastern lowland neighbours. The frontier region can be divided into three zones in a west-east direction:

- Zone I on the eastern foothills of the high Andes where the local chiefdoms (señoríos) and the Incas had common interests not only economically but also as regards security. The Incas established multiethnic mitimaes communities there and organized the defence against the threat from the lowlands; thus fortresses were built and garrisons maintained within this zone, either as a west-east series of simultaneous forts or successive ones built according to the need. There might have risen mutinies among the local communities but these were rapidly surpressed.

- Zone II on the lowlands near the Andes where tre tribes were "bought" with gifts and agreements to co-operate and trade with gifts and agreements. Some threat occurred from the east and southeast, and especially the Chiriguanos caused troubles by invading periodically the higlands of Zone I. It is possible that small fortresses or trading posts with military contingents were established here (e.g. Samaipata is mentioned in historical documents as being situated on Chiriguano territory), but the most fierce attacks brought Chiriguanos far onto the eastern mountains as the case of Cuzcotuyo graphically demonstrates. These aggressions continued during the colonial period against the Spaniards at least until the early 17th century (Combés & Saignes 1991: 37).

- Zone III extends to the eastern lowlands as far as the highlanders, either the Incas themselves or their allies, ventured to trade. These contacts were perhaps only casual and short-lived, and never based on agreements, but nevertheless local historical sources indicate the presence of highlanders as far as on the Brazilian side of the present border between Bolivia and Brazil. - It is a matter of opinion whether we regard this as conquest, control or just contacts.

The boundaries between the zones were never clear and static, the one between Zones I and II was perhaps the sharpest, but especially the boundary between Zones II and III was diffuse and it is impossible to draw it on the map.

This reconstruction of the border zone system remains of course highly conjectural and should be taken only as a working hypothesis for further research. Archaeological investigations are needed especially on the lowland zones in order to verify the possible Inca elements, either structures or ceramic influences, there. That Inca influences, perhaps even Inca presence, reached the lowlands also in the more northerly sections of the borderlands is hinted by certain traditions, supported by archaeological and ethnographical evidence, that the highlanders - in fact already well before the Late Horizon of Peru - had contacts with the lowlanders along the middle Ucayali river in the Peruvian selva (Lathrap 1973: 180, Lathrap et al. 1985), although at least deseases to which the highladers were not resistant made it difficult for them to settle permanently in the lowlands (Gade 1979).

Thus, our information about the Andean foreland fortresses, and especially their correlation with the written accounts, has somewhat improved since Erland Nordenskiöld's time. However, archaeological knowledge concerning the lowlands is still deplorably scanty and should accumulate considerably before we have a clear picture of the borderland of the Inca Empire and of the processes through which the interactions between the highlanders and lowlanders developed.

Prehispanic Earthworks of the Baures Region of the Bolivian Amazon

Summary

The environment of the Amazon region of tropical South America was long considered to be of limited potential. It was commonly believed that in the past, as in the present, the social and political organization of indigenous peoples was simple, that populations were nomadic or widely dispersed over the landscape, and that subsistence was based on hunting, gathering, and small scale agriculture. In the 1960s, the discovery of massive raised field systems, causeways, canals, occupation mounds and other earthworks challenged this perspective. The Llanos de Moxos of the eastern lowlands of Bolivia is one region where prehispanic peoples built a vast infrastructure of earthworks, enabling their culture to flourish over several thousand years. A joint international project of the University of Pennsylvania Museum of Archaeology and Anthropology and the National Institute of Archaeology of Bolivia has been investigating the precolombian land use strategies of the ancient peoples of the Bolivian Amazon region of Baures for two field seasons. The approach used in this project is that of "landscape archaeology."

The native people of Baures were considered to be the most "civilized" group encountered by the early Jesuit missionaries in the Bolivian Amazon. They lived in numerous large villages protected by moats and palisades and constructed large causeways and canals for transportation between settlements. The earthworks mentioned in the ethnohistorical literature were part of a tradition whose history can only be understood through the archaeological record.

We are investigating a large complex of prehispanic earthworks and associated settlements in this region. The project uses many standard archaeological techniques of survey, mapping, and excavation to locate, describe, and spatially record the earthworks and settlements. Computer mapping techniques and computer analysis of imagery recorded by satellite and low flying aircraft orient the daily work in the field and will serve as the basis for a regional Geographic Information System. The project team includes professional archaeologists and archaeology students from the University of Pennsylvania, the National Institute of Archaeology of Bolivia, Universidad T‚cnica del Beni, and the Universidad Mayor San Andres. The research from this project will also be used to help plan, establish, and manage a national park in the Baures region. This project is a feasibility study for a future large scale multidisciplinary investigation in the region.

Detailed Introduction

The discovery of the massive prehispanic earthworks over broad areas in the eastern lowlands of Bolivia in the early 1960s drastically challenged traditional perspectives regarding cultural development in the Amazonian drainage. A pre-1960s archaeological treatment of the Amazon would typically have stressed the environmental limitations to cultural development; predominance of simple societies (bands and tribes); and subsistence systems based on hunting, gathering, and fishing with some limited agriculture in the form of slash and burn (Meggers 1971; Steward and Faron 1959; Steward 1963). The documentation of the prehispanic raised field agriculture in the Beni region of Bolivia (Denevan 1966) and elsewhere in the humid tropical lowlands of South America (Lathrap 1970; Denevan 1966, 1970, 1983) demonstrated that intensive agriculture was possible and that large, dense populations were supported in these areas.

Our project members have been investigating the precolombian land use strategies of the ancient peoples of the Bolivian Amazon region since 1990 (Erickson 1995). Our recent research has focused on Baures located in the Province of It‚nez, Department of the Beni, in the northeast part of the Bolivia. The project conducted intensive exploratory research on the prehispanic earthworks of Baures with a focus on the moated occupation sites on forest islands and the causeway/canal networks of the savannas during two periods of fieldwork in 1995 (of 25 days and 14 days) and one month of fieldwork in 1996 (Erickson et al. 1995). The project includes archaeologists from the University of Pennsylvania, the National Institute of Archaeology of Bolivia, and students from the University of Pennsylvania, Universidad Mayor San Andres (La Paz), and the Universidad T‚cnica del Beni (Trinidad). Collaborating institutions include the University Museum, University of Wisconsin, CORDEBENI, Bolivian Ministry of Tourism, Ministry of the Environment and Sustainable Development, and the regional government of the Department of the Beni and the municipality of Baures.

A "landscape archaeology approach" can be useful for the study of regions and non-occupation site features such as earthworks. The archaeology of landscape focuses on the space between occupation sites, something rarely considered in traditional archaeology (Crumley and Marquardt 1987; Rossignol and Wandsnider 1992; Gleason and Miller 1994). These non-site or off-site cultural features include field walls and boundaries, roads and pathways, markers, alignments, sacred places, places of historical memory, or in the case of the Bolivian Amazon, massive and extensive earthworks (including raised fields, causeways, canals, reservoirs, and mounds). Landscape archaeology attempts to investigate both the environmental and cultural processes involved in the formation of historical landscapes without imposing an environmental determinism. In the Bolivian Amazon the ancient landscape was so dramatically modified that it can be called "anthropogenic" or "human-created" (Denevan 1966, Erickson 1980;

Erickson et al. 1991, 1993, 1994, 1995). In other parts of the world the archaeological study of cultural features in the landscape has provided a window into social organization, spatial order, native cosmology, calendrics, settlement systems, land tenure, and other important issues (Scarborough and Isaac 1993; Gleason and Miller 1994). Methodological advances including remote sensing, Geographic Information Systems, Global Positioning Systems, and computer generated topographic mapping have been effectively used in landscape archaeology. These methods are employed in this project.

The Environment and History of the Baures Region

Baures is the name of a region, a district, a town, a language, and a native ethnic group (Baure). The environment is diverse and characterized by a mix of gallery forests along rivers and lakes, forested islands in the savanna grasslands, vast open grasslands (pampa), extensive wetlands, several navigable rivers, and large shallow lakes. There is a marked wet and dry seasonality in the region, with extensive flooding of the flat landscape during 3-5 months of the year. Despite the presence of tropical laterite soils in many locations, the higher forested ground is considered by local informants to be highly productive. Swidden agriculture and gardening is practiced by the local inhabitants. Today much of the savanna near Baures is devoted to cattle ranching.

A number of early accounts of Baures written by the Jesuits (Altamirano 1891; Eder 1888; Anonymous 1743; Equiluz 1884) in the late 15th and 16th Centuries describe the native peoples, their customs, local landscapes, and colonial mission life. Unlike many areas of the Amazon, Baure apparently did not suffer an early demographic collapse. However, after the missionary Cipriano Barace was killed in 1703, the native peoples suffered greatly under Spanish reprisals, which included violent retaliation, warfare and enslavement. After 1708, the missionaries moved dispersed communities into several mission reduction towns, the central ones being Concepci¢n de Baures (the present town of Baures) and San Martin. The area was noted in the documents as being agriculturally rich, especially for the production of cacao and cotton.

The colonial descriptions provided by the Jesuits provide a rich, although incomplete, picture of the Baure culture. The Jesuits considered the Baure to be the most "civilized" of the ethnicities in the Llanos de Moxos region because they wore cotton clothing ("clean and tractable") and lived in large, well organized villages (Altamirano 1891; Eder 1888) . Hereditary chiefs (aramas) held considerable power over their subjects, especially in relation to agricultural production, mobilization of warriors and agricultural labor, and public order. The villages were large by Amazonian standards and were laid out in formal plans which included streets, spacious public plazas, rings of houses, and large central bebederos (communal men's houses). According to the Jesuits, many of these villages were defended through the construction of deep circular "moats" and wooden palisades enclosing the settlements. Settlements were connected by causeways and canals that enabled year round travel . The picture is one of a densely populated region filled with large, well- organized dispersed settlements taking advantage of the local natural resources.

We speculate that the Baure recorded in the ethnohistorical documents are the descendants of the people who constructed the earthworks found within the forested islands, wetlands, and the savannas. Although some of these earthworks were used during the historical period, it is not known if they were actively being constructed and maintained. The majority of these earthworks were probably constructed and used in the proto-historical or prehispanic period. The disruption caused by conquest, depopulation, resettlement, and missionization during the historical period probably caused the abandonment of these earthworks.

Archaeological Remains in the Baures Region

The first reports of the archaeological remains in Baures are from Nordenski”ld (1916, 1918) who mentions the remains of moated village sites and several large causeways and canals. This work was not followed up until Denevan (1966) described several causeways and canals still in use by the inhabitants of Baures and reported on the moated villages of Baures and Magdalena. In the late 1950s, the geologist Lee (1979, 1995; Pinto Parada 1987) discovered the vast remains of networks of causeways, canals, and settlements in the pampas between the Rio San Joaquin and the Rio San Martin (the "Baures Hydraulic Complex"). Lee and Botega made many flights over the region with scholars and journalists to view the earthwork complex, but the remains were never examined by archaeologists on the ground. The only archaeological research done in the Baures region was conducted by Dougherty and Calandra (1984-5) in the town of Baures and along the Rio Negro and the Rio Blanco. They conducted a series of small test excavations to recover pottery in an attempt to develop a chronology for the area.

In 1995, the Agro-Archaeological Project of the Beni (University of Pennsylvania and National Institute of Archaeology) had the opportunity to do a one week exploratory investigation of the region. The project members were invited by the Corporation of the Department of the Beni and the mayor of Baures to begin an investigation of the archaeological resources of the region, develop plans for a regional archaeological museum, and explore the

possibility establishing a national eco-tourism park and biological reserve within the "Baures Hydraulic Complex." During this short visit, the Project team conducted archaeological survey and mapping of several moated village sites and other earthworks, photographed archaeological pieces in private collections, and established professional contacts with local institutions for future research. A member of the team (Vranich) conducted two brief exploratory surveys (of 10 and 14 days) into the remote heartland of the causeway complexes (Erickson et al. 1995).

The principal archaeological earthwork features in the Baures Region include various forms of moated occupation sites (probably villages), moated forested islands (larger communities), causeways, canals, and reservoirs. To date, no raised fields have been located here. The total extent of these earthworks in Baures is unknown at the moment but the areal distribution has been estimated to be 12,000 km2 (Lee 1995) although the area of continuous distribution earthworks is probably much smaller (Erickson et al. 1995).

Prehispanic Moated Settlements

In 1995 and 1996, our surveys located and mapped 14 separate moated occupation complexes/sites on forested islands near Baures and Bella Vista. The enclosed areas of sites are estimated to range from 1 ha to 5 ha and up to 3 village sites occur on a single forest islands. The moats are impressive earthworks of up to 4 meters deep and 10 meters wide, sometimes with steep sidewalls, and have diameters of between 150 and 350 meters. A number of sites also have multiple concentric moat rings. The forested island site of Jasiaquiri has a series of linear an curvilinear canals that appear to delineate the isla from the savanna enclosing an area of nearly one square mile and those of Bella Vista are possibly even larger enclosures.

The moats surround what appear to be large circular, oval, and rectangular shaped settlements. Domestic pottery sherds were recovered from disturbed areas at the sites of Santiago and Irovy. Probe core sampling demonstrated that the occupation features are shallow. The moat features do not appear to hold water (or only for short periods of time). Their shape and form indicate that they are defensive or to restrict access to the settlements (also supported by the ethnohistorical documents). Other possible alternative functions include use of the sites as elite residences, cemeteries, ritual spaces, hunting traps, and garden sites. Larger, but similar moated village sites have been reported for the Upper Xing£ region of Brazil (Heckenberger 1996) and other regions of Amazonia (Nordenski”ld 1918).

Causeways and Canals

The most impressive landscape feature in Baures are the dense networks of long causeways and canals that cross the savannas, wetlands and forested islands. A (possibly prehispanic) 15 km long causeway and canal connected the towns of Baures and Guacaraje until the 1930s when it was abandoned. Some segments of old causeways between local settlements and ranches are still used today for communication and transportation during the rainy season. The "Baures Hydraulic Complex" located between the Rio San Joaquin and the Rio San Martin to the east of the town of Baures has the densest concentration of these features. There are thousands of linear kilometers of causeways and canals in this zone. Most are remarkably straight. Many cross over one another and some connect to other causeways. There are a number of cases where 2-4 causeways run parallel to each other. On the ground, these causeways are low structures of 0.25-1.0 m in elevation, 4-6 meters wide and often 2-5 km long. Most are badly eroded and many are covered with trees and bushes, a sharp contrast to the surrounding grass covered savanna. Foot traffic would have used the raised roadways and canoe traffic would have been possible in the adjacent canals. The most basic function of these features would have been for communication and transportation between settlements, rivers, and agricultural fields, but it is possible that some of these had a hydraulic function (Lee 1995, Erickson et al. 1995). The obsession with straightness over long distances, the "overengineering" of the designs and construction, and the sheer number of these features indicates that they may have also had a ritual function, possibly associated with astronomy, calendrics, or specific ceremonies.

Our exploratory research on the Baures earthworks attempts to 1) provide a detailed description of earthwork morphology and patterning, 2) document the geographical extent and distribution of the features, 3) determine the function(s) of the structures, and 4) to date the periods of construction, use and abandonment. Using the spatial distribution of forest island occupation sites and the association of occupation settlements connected by networks of causeway and canals (thus assumed to be contemporaneous), we can examine the prehispanic settlement system of the region. This would be extremely difficult in most humid tropical contexts and the Baures region provides some unique advantages of high archaeological visibility of site and earthworks and the actual physical connections between sites. This will help define the prehispanic demography, socio-political organization, and boundaries of the settlements to be further studied in future research.

Methodology

The investigation of the earthworks of Baures has been conducted using remote sensing techniques (digital processing, enhancement, and interpretation of images), ground survey, surface collections, topographic mapping , post-hole coring transects across sites and earthworks, small scale excavations of features, and the recording of artifacts from private collections in the region.

The Project relies heavily on the use of remote sensing, in particular aerial photography (purchased mapping photography and our own oblique photography taken from small aircraft converted to digital format) and satellite digital imagery (LANDSAT and SIR-C radar) of the region of Baures for documentation and interpretation of prehispanic earthworks. The programs Adobe PhotoShop and IDRISI are used to digitally process, enhance, and layer digital images for detection and mapping of earthworks and other cultural features, and to produce vegetation and landuse classifications. This work is being done in the Department of Anthropology Computer Laboratory and the GIS Laboratory of the Department of Landscape Architecture at the University of Pennsylvania. Ground truth from the field will provide information to further refine our interpretations and the digital signatures of specific features on the landscape.

The reconnaissance is conducted on foot and canoe and when available, we use small aircraft to photograph areas where fieldwork is being conducted. The prehispanic moated occupation sites only occur on island forests and gallery forests, thus are relatively easy to locate and study. Surface collections are made where subsurface disturbances have exposed archaeological materials (gardens, pathways, house clearings, and river cuts). All major sites are mapped with tape and compass. Many moated sites have been mapped with an EDM Total Station to produce detailed micro-topographic plans. We can produce computer generated contour maps that can be layered with the aerial photographs of the same site. Several sites have been examined using a 5" coring auger to sample soils (to a maximum depth of 1.25m) at 5m intervals along transects across sites (closer intervals are used in moats). If stratified middens are located, we plan to excavate 2 x 2 meter test trenches in them to recover material to date sites and begin chronology building. These strategies should be sufficient to determine site function and provide a means of dating the sites.

Causeways and canals are investigated using the same methodology that we used for the study of raised fields, causeways and canals in central Moxos (Erickson 1995). Causeways are located and defined on aerial photographs. These are verified and mapped on the ground during survey. Earthworks not visible on the images are added to the master maps. Orientations are determined and topographic transects across canals and causeways are drawn for each earthwork. Several areas are being selected for intensive topographic mapping using the EDM. This will be relatively easy because most of these earthworks are located in the open savanna. Calculations can be made to estimate the labor involved in construction.

Research Opportunities

The Project provides a wonderful opportunity for students at the University of Pennsylvania interested in Geographic Information Systems (GIS), computer graphics, landscape architecture, conservation, sustainable development, ecotourism, and the environment. This is a chance to become involved in a important project to investigate long term ancient land use in the Bolivian Amazon and to establish a national park/ecological reserve to protect and manage the archaeological and biological resources of the region might otherwise be destroyed through colonization by ranchers and agriculturalists. The park would provide research opportunities scholars and potential income from eco-tourism for local peoples.

A major goal of the Baures Archaeological Project is the creation of a Geographic Information System of the region of the "Prehispanic Hydraulic Complex of Baures". We are beginning to processing maps and images in the Computer Laboratory of the Department of Anthropology of the University of Pennsylvania. These will be valuable for precisely locating sites, determining the environmental context of a site (vegetation, soils, topography, hydrology), and eventually for establishing a Geographic Information System for the region. Much of the work done thus far has been limited to single layer remote sensing applications (vegetation classification, basic mapping, digital enhancement of images).

The project also has an applied component. The national and local governments have recently discussed plans with international funding agencies to create an "eco- tourism" park and biological reserve in the region of the "Prehispanic Hydraulic Complex of Baures" (Lee 1995). The region was heavily occupied by native peoples before the arrive of the Spanish in the 1600s, but quickly depopulated because of Jesuit policies of centralizing populations in mission towns, slaving, warfare, and introduced diseases from the Old World. The region would be an ideal place to study the processes of at least 500 years of environmental recovery in a tropical context that was totally transformed by the actions of its ancient inhabitants. At the moment, no one lives permanently in the area and it is not used for farming or ranching. There is a strong movement to formally establish the park before colonists move

into the area. The archaeological earthworks and sites would be protected, in addition to the fauna and flora of the zone. The plan includes hiring native peoples to serve as park rangers and to establish the necessary infrastructure to conduct research and tourism. Our preliminary study of the area in 1995 and 1996 provides important information to support the effort to establish the park but more detailed inventory of resources and spatial data are necessary.

Research Opportunities for Students Include:making a detailed accurate map of the region based on remote sensing delineate potential park boundaries based on cultural and natural criteria hydraulic mapping of the region using remote sensingestablishment of an inventory of particular resources within the park area (palms, grasslands, lakes, rivers)map the dynamics of seasonal inundation (map the area effected by flooding during the rainy season) based on remote sensing.produce a digital terrain map of the regionsimulate flood conditions with different rainfall regimes over time based on the digital terrain map.map the forest island and savanna boundariesdevelop predictive models for prehispanic settlement locationsmap the encroachment of ranches and communities of colonists on the area surrounding the proposed park. locate and map the ancient causeway networks, define their patterning and orientationsanalyze the spatial logic of ancient causeway networks to determine their potential functions (transportation and communication, astronomy and calendrics, ceremonial use, fish weirs, water management, etc.).development of pattern recognition algorithms for specific archaeological landscape features (earthworks, moated village sites, canals, and causeways) or human-caused environmental patterning.

Many of the above projects could be developed as "group projects" involving the collaboration of several students. Many of these projects could be developed into Masters Theses and PhD dissertations for graduate students.

Additional volunteers are needed for the preparation of ancient landscape renderings and computer graphics for research needs and scientific publication of the results of the archaeological project in the Bolivian Amazon. Academic credit can be arranged.

Please see the WWW home page VOLUNTEERS WANTED:ILLUSTRATION OF ARCHAEOLOGICAL LANDSCAPES:

Resources Available to the Baures Project:hundreds of low altitude, oblique aerial photographs in the form of color slides and black and white negatives taken from small aircraft in 1995 and 1996. a series of 9 x 9 inch black and white aerial photographs (1:40,000 scale) covering most of the regiona number of 1 x 1 meter enlargements of the above mentioned aerial photographs.two LANDSAT digital images of the region (available to the project in January 1997) topographic maps of 1:50,000 scale of most of the regiona geological map of the region at 1:150,000 scalesome ground truth information for selected sites

Global Positioning System reference points for numerous sites (suitable for georeferencing and determination of scales).

In addition, we may be able to obtain LANDSAT TM images of the region from the archives at Cornell University and a proposal has been submitted to obtain SPOT imagery of the region. Local and government officials, public and private institutions in Bolivia have offered to aid the project in many ways and have fully supported the idea of continued research in the region. A well-equipped remote sensing and GIS computer laboratory will be established in the regional capital Trinidad during this year and officials have promised help with purchase of imagery necessary to prepare a GIS of the region.

The Computer Laboratory of the Department of Anthropology has a powerful Pentium computer capable of running remote sensing applications, Geographic Information System software, and computer graphics software. The machine has a high resolution monitor, sufficient RAM, and ample harddisk drive space for storage of large digital images and is connected to Penn's ethernet system. The Department owns a flat bed, slide scanner, and several high quality laser printers

Broader Implications and Importance of the Research

This project will provide information on one of the more complex prehispanic societies in Amazonia. The elaborate construction of earthworks consisting of moated villages and vast networks of canals and causeways is unusual in the lowland tropics of South America. Until recently, little archaeological research had been conducted on earthworks in these regions. Big questions are still asked regarding these landscape features such as Who built these structures? When were they constructed, used and abandoned? What purpose did they serve? What sociopolitical organization and demographic system was associated with these works? The region of Baures, Department of the Beni, Bolivia, is an ideal place to begin to address these important issues. The density of large interconnected settlements indicates that these peoples were quite different from the traditional conception of "simple Amazonian societies." Because occupation sites are easily identified and often connected one to another by formal earthworks, it will be possible to establish a site settlement pattern and define which sites are interacting with each other. Even the small exploratory projects have provided insight into the social and political organization of the region.

The project also has an applied component. The national and local governments have recently discussed plans with international funding agencies to create an "eco- tourism" park and biological reserve in the region of the Baures Hydraulic Complex (Lee 1995). At the moment, no one lives permanently in the area and it is not used for farming or ranching. There is a movement to formally establish the park before colonists move into the area. The archaeological resources would be protected, in addition to the fauna and flora of the zone. The plan includes hiring native peoples to serve as park rangers. Our preliminary study of the area in 1995 and 1996 provides important information to support the effort to establish the park (inventory of archaeological resources, maps of vegetation and land use potential, physical boundaries of the park, etc.). The region would be an ideal place to study the processes of at least 500 years of environmental recovery in a tropical context that was totally transformed by the actions of its ancient inhabitants.

The Lost Art of the Waru Waru

Surrounding Lake Titicaca, on Peru's southern border with Bolivia, is the altiplano, a vast plain 12,500 feet above sea level. Much of the land is pasture, but scattered here and there, for as far as the eye can see, are patches of corrugated land. Each patch is divided into long narrow strips separated by furrows, some of which contain puddles of water. Closer inspection reveals that the tops of the strips are populated by dry, hardy grasses whereas the vegetation in the furrows is lush and green. The local farmers call these strange topographical features waru waru or camellones. Until 1981, however, the local farmers had no idea that these represented persisting evidence of the remarkable engineering and agricultural skills of their ancestors. The fact that waru waru cover some 205,000 acres of land around Lake Titicaca suggests that the ancient inhabitants of the altiplano had hit on a system that successfully tackled the considerable environmental constraints of farming the area.

Archaeologists are now convinced that the waru waru were built specifically to protect crops from frost damage and floods. In 1981, Clark Erickson, of the University of Illinois, recognized the archaeological significance of waru waru. But he also wondered whether they might not serve modern farmers as well as they did their ancestors. Erickson began to rebuild some of the raised fields. Using traditional Andean tools, local farmers planted an experimental field with potatoes, quinoa and canihua. Waru waru potato yields were more than 8 tons per hectare, compared with the average yield for the region of 2 to 3 tons per hectare. Today some 3,700 acres of raised fields have been reconstructed. The Peruvian Department of Agriculture is convinced of the value of waru waru in the region. The government now offers loans to farmers for rebuilding the fields.[NEW SCIENTIST, 5/12/88, VOL. 118 (1612;PP. 50-51) ]

Defining the Prehispanic Andean Community:An Application of the Archaeology of Landscapesby Dr. Clark L. EricksonAssociate ProfessorDepartment of AnthropologyUniversity of PennsylvaniaUniversity of Pennsylvania MuseumEmail: cerickso@sas.upenn.edu

The agrarian community in the central Andes (Peru and Bolivia) has been the subject of numerous studies by historians and ethnographers. Archaeologists employ these studies both as deductive models to test in the field and as inductive explanations of archaeological record. Others argue that, because of

the changes wrought by the European Conquest and modern world systems, historic and ethnographic communities bear little resemblance to the prehispanic predecessors. Archaeologists reduce the community to a single settlement, or cluster of small settlements, usually the sites on the lowest rung on a hierarchy of settlements. The inhabitants that made up agrarian communities are portrayed as faceless masses in the political economy models that frame prehistory in a top-down approach.

I argue that the Andean community is particularly amenable to archaeological study because its ethnographic and historical signature is so clearly grounded in fixed territories, residence, land tenure, and landscape capital (defined here as multigenerational infrastructure and knowledge systems pertaining to settlement, communication, transportation, farmland, and identity). Andean peoples, past and present, provide us with a range of definitions of community rooted in the physical landscape. In using Andean ethnography and history to develop a spatial model of social organization, I do not assume that Andean communities are homogeneous or static. The ethnographic and historical records provide evidence for both change and continuity in agrarian social organization. The archaeological record documents change and continuity as a complex palimpsest of cultural features on the landscape. Andean agrarian communities do not simply occupy land; they are physically embedded in it.

Historical and contemporary ethnographic studies provide a dynamic model of the Andean community in space and time. Participation in cooperative work ventures (primarily reciprocal labor relations) and common celebration of ritual events defines membership in community and sub-community groups (ayllus, parcialidades). This membership has material correlates in the landscape and structures the physical boundaries between communities. Instead of assuming change or continuity, these models of the community area tested and evaluated against the archaeological record. Anomalies and discontinuities between the models and the archaeological evidence provide insights about the origins of agrarian lifeways, state formation processes, responses to physical and social environmental change, and resistance to state authority.

In this presentation, I will examine the archaeological evidence for agrarian communities in the Lake Titicaca Basin of Peru and Bolivia using a landscape approach. Prehispanic farming communities completely transformed the physical environment into a cultural or anthropogenic landscape. In terms of labor, volume of materials, and formal design, much of this landscape transformation is monumental in scale (rivaling the traditionally recognized monuments of ceremonial and political centers associated with centralized state societies). Analysis of the formal patterning of landscape features provide powerful means to study the structures of everyday life, land tenure, local worldview and aesthetics, social interaction, and agency. The archaeology of landscapes seeks to people the past and focus attention on the people ignored in traditional approaches to prehistory.