In a corner of the Amazon, to the east of Acre, near the border with Bolivia, there was a time when the gods seem to have been geometric; and this period probably began long before scientists had previously thought. Twelve radiocarbon date checks carried out in different sectors of three archaeological sites in this region indicate that the construction of the so-called geoglyphs – large designs excavated in the forest soil by an as yet indeterminate pre-Columbian culture, which admired the straight lines of squares and rectangles and the round features of circles and ovals – started at least two thousand years ago. Coordinated by archaeologist Denise Schaan, from the Federal University of Pará (UFPA), the new study, whose article is being finished for submission to be published in a scientific journal, extends the chronology of the Amazon culture of geoglyphs. Until now there has only been data from one date check, conducted in 2003 in Acre by Finnish researchers on one of these archaeological sites. This placed the designs as having been produced sometime in the thirteenth or fourteenth centuries.
Made from the remains of burned charcoal found in a geological layer that is rich in pieces of pottery, an indication that there was some human presence in that area, the new series of date checks also suggests that the unknown authors of the geoglyphs may have disappeared before the arrival of the Europeans in the Americas. None of the three sites studied (Fazenda Colorada, Jacó Sá and Severino Calazas), located in a radius of 20 kilometers on a plateau of firm ground that does not flood, among the valleys of the Acre and Iquiri Rivers, has so far supplied elements to indicate that they were inhabited by tribes more than 500 years ago. “The result of the date checks was a surprise,” says Denise, who has been leading the archaeological work on geoglyphs since 2005 with funds from the CNPq (National Council for Scientific and Technological Development), from the Finnish Academy of Science and Letters and from the State of Acre.
The age of the geometric designs, molded in the soil of the Amazon by means of the removal of a large amount of earth, is not the only controversial point under review. The primary function of these sites, which may present more than one type of geoglyph and traces of ancient highways, is also open to debate. Since the 1970’s, when parts of Acre began being cleared for crop and livestock farming activities and the first geoglyphs were sighted at points until then covered by the forest, researchers have questioned why the ancient inhabitants of the region sculpted low relief circles and squares in the soil. The initial hypothesis, that the constructions, whose outlines are formed by continuous ditches dug out of the ground, could have had defensive functions similar to a fort, seems to make less and less sense. Recent excavations, carried out at almost a dozen sites in Acre where these designs have been found , indicate that these places were not primarily used as dwellings by ancient peoples. Like a type of tribal square, the inner area of the geoglyphs must have been used for ceremonies. “The archaeological evidence suggests that these sites were used for special meetings, religious ceremonies and only occasionally as a village,” says Denise.
When the field investigations began, the researchers were working on the idea that sites with geoglyphs would be able to supply some type of evidence of large scale human occupation for a long period in the surrounding area. After all, it is more than reasonable to suppose that the people responsible for making large and accurate designs in the soil were numerous and had a complex social structure. “The builders of the geoglyphs had no stones in that region, but did great work on the land that required power and organizational skills similar to those of other ancient civilizations,” says archaeologist Martti Pärssinen, from the Ibero-American Institute of Finland, based in Madrid, who is collaborating with the Brazilian team and is also one of the authors of the study giving the new date checks of the Acrean geoglyphs.
On average, the inner area of a geoglyph varies from 1 to 3 hectares. The smaller figures generally have rounded lines while the largest can be either circles or squares. On the sites studied, the depth of the holes in the soil that form the outlines of the designs varied from 35 centimeters to 5 meters and the width of the trenches varied from 1.75 m. to 20 m. The earth removed to make the trenches was used by the architects of the geoglyphs to make small walls as much as 1.5 m. high, which followed the outlines of the figures. To carry out all this work, thousands of people must have lived at some stage in the areas surrounding the geoglyphs and worked in a coordinated way to build them. However, the archaeological findings on the sites investigated in detail yet again do not ratify the initial assumption of the researchers.
Preserved human bones have not been found anywhere. Neither are there marks of the so-called black earth, a type of black soil that is very common in other parts of the Amazon Region and that is formed from the organic remains produced by the prolonged human occupation of an area. The few artifacts associated with a material culture, generally pieces of pottery, were retrieved from the top or bottom of the trenches that form the geometric lines, or in small mounds of earth, probably the remains of pre-historic dwellings that are located right alongside the outlines of the geoglyphs. Nothing really relevant was retrieved from within the flat area marked out by the mysterious circles and squares excavated in the ground. “We still need to find the places where the dwellings and cemeteries of the people who constructed the geoglyphs were located,” says paleontologist Alceu Ranzi, today a retired professor from the Federal University of Acre (Ufac), who (re)discovered the designs in the soil over the last two decades. “They must have lived somewhere not too far from the sites.”
Aerospace technology has been an ally of the archaeologists in their task of locating and studying the Amazon Region sites with geoglyphs. Being somewhat far away and above the designs in an airplane, or using the lenses of a satellite for eyes, facilitates the work of looking for large geometric figures in the midst of deforested areas (if there is still a forest this does not work). The scientists initially used free images from the Google Earth service to look for new occurrences of the designs. As from 2007, with the support of the government of Acre, they have also obtained images from the Taiwanese satellite Formosat-2, which provides a broader cover. By using these remote prospection tools the number of known sites with geoglyphs soared: from 32 in 2005, to 150 two years later; at present, the number stands at around 300. These are figures only for Acre, which seems to have been the region where the designs are concentrated. They may spread out over a part of this state, that has an area of 25,000 sq.km., 16 times the size of the city of São Paulo. In the neighboring states of Amazonas and Rondônia and also in Bolivia, areas with geoglyphs have been identified using this methodology. “It’s no longer that easy to find new sites, because we’ve already done several systematic sweeps,” explains geographer Antonia Barbosa, from Ufac, a member of the Brazilian team that studied the geoglyphs. “When we started working with satellite images we found some ten sites in one sweep. Today, if we’re lucky, we might find one or two.”
There is no hard evidence about who built the geoglyphs or how long this task took them. The construction of trenches and walls for surrounding houses and villages was already happening in Europe approximately 10,000 years ago, with the beginnings of agriculture. However, in the Amazon Region, this type of construction is much rarer. Since there are no indications so far that the frontier of Acre with Bolivia was the dwelling place of a unique and great lost civilization, where no one has managed to find the remains of any houses or villages, the archaeologists started working with an intermediary scenario. It is unlikely that there was an enormous lost empire that worshipped geometric gods in this corner of the Amazon, but perhaps there were two or three still semi-nomadic peoples, spread out in small villages (today more difficult to find), who shared some common cultural features, such as making geoglyphs. “The geoglyph society was in one way complex, but it was in a formative stage, one of transition,” says archaeologist Sanna Saunaluoma, from the University of Helsinki, who is studying the designs both in Bolivia and in Acre, on the Brazilian side of the border.
Members of the Tacana and Aruaque tribes, who today live on the Bolivian and Brazilian side, respectively, of this bi-national frontier, might be the descendants of the people who traditionally built enormous circles and squares in the ground. However, if they were once the practitioners of this common tradition, they no longer engage in it. To make the picture more unclear, there is no evidence that the two tribes were actually in this area at the time when the geoglyphs were made, nor is it known what territorial boundary separated them. A clue, albeit a tenuous one, that at least one of these races, the Tacana, may have constructed geoglyphs comes from a text from the late nineteenth century. The writing concerns a meeting on the border with Bolivia between a Brazilian colonel and 200 Indians who lived in a very well-organized village and worshipped geometric gods, carvedRepublish