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Pre-Columbian Amazon-Scale Transformations

Final Report Summary - PAST (Pre-Columbian Amazon-Scale Transformations)

The PAST project investigated the influence of late pre-Columbian (1000-1492 A.D.) land use on Amazonian landscapes and the impact and modern legacy of the 1492 Columbian Encounter (CE) through the comparative study of pre-Columbian land uses in different regions of Amazonia. Our unique interdisciplinary approach combining archaeology, archaeobotany, palaeoecology, paleoclimate, botany, soil science and remote sensing has allowed us to explore human environmental interactions with unprecedented detailed while being able to connect the past with the present and allowing us to explore the modern legacy of pre-Columbian land use in the Amazon.
Our investigations in the Lower Amazon showed that modern forest vegetation is the legacy of 4,500 years of polyculture agroforestry in the eastern Amazon characterized by an abrupt enrichment of edible forest species combined with the cultivation of multiple annual crops (maize, manioc, sweet potato and squash). These millennial-scale pre-Columbian polyculture agroforestry systems have left an enduring legacy on the modern enrichment of edible plants, demonstrating the important role of past indigenous land management in shaping modern forest ecosystems in the eastern Amazon with implications for modern hyperdominance of useful species in the Amazon. Our work in the southern rim of the Amazon showed that an 1800 km stretch of southern Amazonia was continually occupied by earth-building cultures living in fortified villages ~Cal AD 1250–1500. By modelling the distribution of earthworks in this broad region utilising existing and newly discovered sites along with environmental, terrain, and ethnographic parameters, we predicted that earthworks will be found over ~400,000 km2 of southern Amazonia and conclude that the interfluves and minor tributaries of southern Amazonia sustained high population densities (between 1-5 million people). Our work has changed the view of this largely unexplored region that was traditionally supposed to be occupied by small groups. In the westernmost section of the southern rim of the Amazon (Upper Purus River), our remote sensing, survey and excavation work revealed well-planned regional systems of mounded circular villages regularly spaced at about 2.5 km connected by radiating roads.
We also documented the domestication of Oryza sp. wild rice by the mid-Holocene residents of the Monte Castelo shell mound (SW Amazonia) starting at approximately 4,000 cal. yr bp, evidenced by increasingly larger rice husk phytoliths. We provided evidence for the domestication of wild rice in a region of the Amazon that was also probably the cradle of domestication of other major crops such as cassava (Manihot esculenta), peanut (Arachis hypogaea) and chilli pepper (Capsicum sp.). These results underline the role of wetlands as prime habitats for plant domestication worldwide.
The compilation and integration, for the first time, of a large Amazonian database, has allowed us to explore questions that were not possible before given the dispersed nature and lack of integration of extant data. For example, we synthesised the most significant transformations observed in the archaeological record across six regions of the Amazon during the Late Holocene, where research has been more intensive, chronologies are robust, and pre-Columbian land use patterns are better understood and compare them with regional-scale climate change. The results show that archaeological cultures with high population densities, hierarchy of settlements, ruling elite and intensive land use systems had become increasingly more vulnerable to external factors, such as increased climate variability, causing their overall cultural reorganisation and/or collapse when faced with climate perturbations.