Pre-Columbian Geometric Earthworks in the Upper Purus: A Complex Society in Western Amazonia
Parssinen, Martti, Schaan, Denise, Ranzi, Alceu, Antiquity
According to mid-twentieth-century neo-evolutionist interpretations of cultural development in the South American lowlands, pre-European Amazonian societies were mainly considered to be primitive egalitarian tribes living in small, impermanent villages in a hostile environment, unable to develop complex socio-political institutions (Steward 1948; Meggers 1954). Although historical accounts mentioned that floodplain river banks and islands were heavily populated by chiefdoms with village leaders and superior lords, some students of Amazonian archaeology and ethnology emphasised important differences between floodplain (varzea) and upland (terra firme) ecosystems. According to Lathrap's model, for example, the varzea constantly attracted peoples due to its bountiful resources, especially aquatic fauna and good alluvial soils; but, as population pressure over limited land took its toll, they were forced to flee to the hinterland terra firme, where their cultural levei decreased (Lathrap 1968, 1970). In her own way, Meggers (1991, 1995) also acknowledged higher levels of cultural complexity for varzea peoples, where some level of social hierarchy and elaborate material culture could develop, thanks to better soils. In her account, terra firme peoples remained demographically smaller and less complex, and were forced to live as hunters, collectors and semi-sedentary slash-and-burn cultivators.
Taking a different avenue to explain the differences between varzea and terra firme, Carneiro (1970) proposed that ecological pressure, caused by too many people desiring limited productive land, was responsible for dragging people into war and eventually gave rise to social stratification. But Carneiro (1960) did not dismiss the terra firme as a place suitable for supporting dense populations, demonstrating, in his upper Xingu example, that a manioc subsistence economy could provide the necessary caloric intake to support large and sedentary populations. Roosevelt (1980), for her part, also had an important role in defending the varzeal terra firme dichotomy, emphasising the fact that the alluvial soils of the varzea were critical for supporting the indigenous development of chiefdoms, an idea not backed up by neo-evolutionist determinism, which always gave priority to outside cultural developments. However, in her 1991 work, she already recognised that some of the terra firme soils were geologically different, citing the ceremonial earthwork monuments of Ecuadorian Amazon (Porras 1987), as an example of social complexity back in the hinterland (Roosevelt 1991).
As we can see, although scholars had different ideas on how to account for the differences between the two main Amazonian environments, the basic dichotomy between varzea (floodplain) and terra firme (interfluvial hinterland) remained valid for some time. In fact, given the scarcity of archaeological data for hinterland areas, researchers concentrated their efforts in trying to figure out how social complexity arose among floodplain societies (Carneiro 1970, 1987; Roosevelt 1993), accepting, even if not explicitly, that terra firme peoples had remained smaller and simpler.
In the flooded areas of the Amazon periphery--the Baures region of Bolivia, and on Marajo island, located at the estuary of the Amazon river (Figure 1)--Steward and Meggers supposed the undeniable signs of social complexity to have resulted from migration from the Andean highlands. Subsequent research has shown rather that social complexity developed indigenously, with the use of sophisticated landscape management techniques such as elevated terraces for agriculture and living, as well as dams and fishponds to manage aquatic fauna in order to guarantee the necessary protein intake (Denevan 1966; Erickson 1980, 2000; Roosevelt 1991; Schaan 2004, 2008). Since the late 1980s, researchers have found evidence of complex pre-European societies in Amazonian upland areas, such as in the Ecuadorian Amazon, where Porras (1987) and Salazar (1998) have found earthworks such as mounds and sunken plazas, and in the upper Xingu, where Heckenberger and his colleagues have described regional integrated systems, identified by villages with central plazas, as well as extensive landscape modifications with moats, roads and bridges (Heckenberger et al. …