Multidisciplinary investigations at the Los Ajos archaeological mound complex in the wetlands of southeastern Uruguay challenge the traditional view that the La Plata basin was inhabited by simple groups of hunters and gatherers for much of the pre-Hispanic era. Here we report new archaeological, palaeoecological and botanical data indicating that during an increasingly drier mid-Holocene, at around 4,190 radiocarbon (14C) years before present (bp), Los Ajos became a permanent circular plaza village, and its inhabitants adopted the earliest cultivars known in southern South America. The architectural plan of Los Ajos during the following Ceramic Mound Period (around 3,000-500 14C yr bp) is similar to, but earlier than, settlement patterns demonstrated in Amazonia, revealing a new and independent architectural tradition for South America.

While large-scale pre-Columbian human occupation and ecological disturbance have been demonstrated close to major Amazonian waterways, less is known of sites in terra firme settings. Palaeoecological analyses of two lake districts in central and western Amazonia reveal long histories of occupation and land use. At both locations, human activity was centred on one of the lakes, while the others were either lightly used or unused. These analyses indicate that the scale of human impacts in these terra firme settings is localized and probably strongly influenced by the presence of a permanent open-water body. Evidence is found of forest clearance and cultivation of maize and manioc. These data are directly relevant to the resilience of Amazonian conservation, as they do not support the contention that all of Amazonia is a 'built landscape' and therefore a product of past human land use.

Aim  To investigate the influence of Holocene climatic and human‐induced changes on a region of high biodiversity in southern Peruvian Amazonia. Location  Four palaeoecological records from separate lakes within a lake district close to the modern city of Puerto Maldonado, Peru. Results  The lakes provide a palaeoecological record spanning the last 8200 years. A mid‐Holocene dry event is documented in all of the records that extend back > 6000 years. The dry event appears to have lasted from c. 7200 yr bp until c. 3300 yr bp. The onset of wetter conditions coincides with the formation of the youngest of the four lakes. The earliest occupation of these sites is inferred from the presence of charcoal at 7200 yr bp, and the first crop pollen is found at 3630 yr bp. Lakes that were regularly occupied were colonized soon after they formed. A reduction in charcoal concentration and the absence of crop pollen after c. 500 bp in all lakes is consistent with site abandonment following conquest. Main conclusions  The mid‐Holocene dry event is suggested to be part of a time‐transgressive drying that tracked from north to south in both the Andes and the Amazon lowlands. The last millennium may represent the period of highest sustained lake levels within the Holocene. The proximity of the four lakes allows a landscape‐scale analysis of the spatial extent of human disturbance centred on a known site of human occupation and reveals the highly localized nature of pre‐Columbian anthropogenic disturbance in Amazonian landscapes. Inferences regarding widespread pre‐Columbian landscape modification by indigenous peoples must take into account key site attributes, such as seasonality and proximity to rivers.

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