Amazonian archaeology has made major advances in recent decades, particularly in understanding coupled human environmental systems. Like other tropical forest regions, prehistoric social formations were long portrayed as small-scale, dispersed communities that differed little in organization from recent indigenous societies and had negligible impacts on the essentially pristine forest. Archaeology documents substantial variation that, while showing similarities to other world regions , presents novel pathways of early foraging and domestication, semi-intensive resource management, and domesticated landscapes associated with diverse small-and medium-sized complex societies. Late prehistoric regional polities were articulated in broad regional political economies, which collapsed in the aftermath of European contact. Field methods have also changed dramatically through in-depth local and regional studies, interdisciplinary approaches, and multicul-tural collaborations, notably with indigenous peoples. Contemporary research highlights questions of scale, perspective, and agency, including concerns for representation, public archaeology, indigenous cultural heritage, and conservation of the region's remarkable cultural and ecological resources. 251

The use of Niche Construction Theory in archaeological research demands that we establish empirically how human-constructed niches acted as legacies that shaped the selection pressures affecting past human populations. One potential approach is to examine whether human demography changed as a result of the continued use of landscapes enduringly transformed by past societies. This paper presents proxies for Amazonian population growth during the late Holocene and discusses their significance within the broader context of landscape legacies resulting from cumulative anthropic environmental alteration during pre-Columbian times.

Traditional views of Amazonian habitation in the deep past revolve around environmental limitations on cultural development. This thesis challenges traditional perceptions of Amazonian societies as environmentally determined and adds to our understanding of ancient human occupation and modification of Amazonian landscapes. Anthropogenic landscapes are the product of complex human-environment processes that form distinct features in the landscape, which materially preserve and reflect human behavior. Anthropogenic landscapes in Amazonia likely date back to human colonization of the region around 16,000 BP. Since colonization, humans have been marking, modifying, managing, and engineering the landscape resulting in a mosaic of anthropogenic landscape features across Amazonia. The diversity of ancient landscapes documented in Amazonia reflects the cultural heterogeneity that existed in the past. This research explores the complex human-environmental processes that form distinct, identifiable, lasting features on the landscape and what these features can illuminate about past human behavior and human-environment interaction in Amazonia. Data for this research was collected by the Tupinambarana Project at the pre-Columbian site, Macurany, located along the Middle Amazon River in Parintins, Brazil. Survey and topography revealed four distinct classes of anthropogenic landscape features at the site, including ports, middens, terra preta, and cultural forests. These features are clearly the result of anthropogenesis and represent a range of subsistence, settlement, and infrastructure-building activities pointing to a society that was actively engaged with modifying the surrounding landscape. Geospatial analysis of the patterning of landscape features evidenced at Macurany suggest social organization was decentralized. The notion of a permanent, extensive, continuously settled, and decentralized society practicing intensive landscape engineering in pre-Columbian Amazonia challenges traditional perceptions of habitation density and early urbanization in Amazonia. This research contributes towards an understanding of human-environment interaction, landscape formation processes and urbanization in pre-Columbian Amazonia.

Amazonian earthworks have a variety of forms and sizes, and are found in different geographical and ecological locations, indicating separate time periods, distinct cultural affiliations, and diverse functions. Because research on pre-Columbian earthworks has only recently begun, a number of basic questions concerning the function and chronology of these structures, and the ethno-cultural and socio-political relationships of the societies who created them still remain unanswered. The main aim of this dissertation, consisting of four peer-reviewed articles and a synthesis paper, is to build new knowledge and expand on the existing, but still noticeably sparse, data on the region's pre-Columbian earthworking cultures. It proposes a hypothesis of the existence of relatively early sedentary interfluvial populations with rather organized and peculiar societal and ideological systems in southwestern Amazonia. This suggestion challenges the conventional view of ancient Amazonian peoples being non-sedentary, with an egalitarian social organization and an inability to alter and manage the environment in which they lived. This dissertation presents and discusses the results of archaeological fieldwork undertaken at earthwork sites in two neighboring frontier regions in southwestern Amazonia: the region of Riberalta in Bolivia and the eastern state of Acre in Brasil. The Bolivian sites are interpreted as permanent settlements, while the Acrean earthworks were constructed principally for ceremonial purposes. The earthworks documented in the Riberalta region are structurally simpler than the ones studied in Acre and are found in slightly different locations, e.g., on high river bluffs or inland only a few kilometers from the main rivers. In Acre, the sites are located on high interfluvial plateaus near minor watercourses. The earthwork building practice prevailed in the Riberalta region from around 200 B.C. until the period of European contact, whereas the geometric earthwork tradition began earlier in Acre, around 1200 B.C., if not before. By the tenth century A.D., the regional confederation that created the geometric enclosures was already disintegrating. Even so, some sites apparently remained in use until the fourteenth century A.D. Chronologically and culturally, these earthworking peoples were formative-stage societies demonstrating emerging sedentism and evolving socio-organizational structures, and in Acre in particular, a society united by a highly developed ideological system materialized in the geometric enclosure architecture.

The emergence of sedentism and agriculture in Amazonia continues to sit uncomfortably within accounts of South American pre-Columbian history. This is partially because deep-seated models were formulated when only ceramic evidence was known, partly because newer data continue to defy simple explanations, and partially because many discussions continue to ignore evidence of pre-Columbian anthropogenic landscape transformations. This paper presents the results of recent geoarchaeological research on Amazonian anthropogenic soils. It advances the argument that properties of two different types of soils, terras pretas and terras mulatas, support their interpretation as correlates of, respectively, past settlement areas and fields where spatially-intensive, organic amendment-reliant cultivation took place. This assessment identifies anthropogenic soil formation as a hallmark of the Amazonian Formative and prompts questions about when similar forms of enrichment first appear in the Amazon basin. The paper reviews evidence for embryonic anthrosol formation to highlight its significance for understanding the domestication of a key Amazonian crop: manioc (Manihot esculenta ssp. esculenta). A model for manioc domestication that incorporates anthropogenic soils outlines some scenarios which link the distribution of its two broader varieties—sweet and bitter manioc—with the widespread appearance of Amazonian anthropogenic dark earths during the first millennium AD.