Abstract
It has recently been argued that pre-Columbian societies in the greater Amazon basin during the Late Holocene were subject to “adaptive cycling”. In this model, cultures practicing “intensive” land use practices, such as raised field agriculture, were vulnerable to perturbations in hydroclimate, whereas “extensive” land use patterns, such as polyculture agroforestry, are viewed as more resilient to climate change. On the basis of radiocarbon data, the relative rise and fall of late pre-Columbian cultures and their inferred patterns of land use in six regions are highlighted to exemplify this model. This paper re-examines the radiocarbon evidence marshalled in favour of adaptive cycling, demonstrating that alleged temporal patterning in these data are overwhelmingly likely due to a combination of sampling effects, lack of statistical controls, and unacknowledged uncertainties that are inherent to radiocarbon dating. The outcome of this combination of factors seriously limits the possibility of cross-referencing archaeological data with palaeo-ecological and -climatological data without controlling for these effects, undermining the central archaeological pillar in support of adaptive cycling in Amazonia. This paper illustrates examples of such mitigation measures and provides the code to replicate them. Suggestions for how to overcome the serious limitations identified in the Late Holocene radiocarbon record of Amazonia are presented in the context of ongoing debates on inferring climatic causation in archaeological and historical datasets.
Highlights
A recent perspective paper in Nature Ecology and Evolution [1] proposes that late pre-Columbian societies in Amazonia that possessed intensive systems of land use were vulnerable to changes in hydroclimate
(14 C) data, which underpin the archaeological component of this model, are calibrated and aggregated into summed probability distributions (SPDs) [2] to illustrate the relative rise and fall of different land use systems over time
A closer integration of palaeo-ecology and -climatology with archaeology is timely [4]. If such a synthesis is to be achieved in future research, archaeology must hold up its side of the bargain and make allied disciplines fully aware of the uncertainties that affect much of our data [5]
Summary
A recent perspective paper in Nature Ecology and Evolution [1] proposes that late pre-Columbian societies in Amazonia that possessed intensive systems of land use were vulnerable to changes in hydroclimate. (ii) absent sensitivity analysis, and (iii) inherent imprecision combined with uncertainty are largely responsible for the patterns of archaeological activity reported in the paper [1] These problems are mutually dependent and reinforcing, which together greatly undermine the terms on which the adaptive cycles model is advanced. Methods for identifying and handling the issues outlined above are readily available in the statistical packages already employed by De Souza et al (notably rcarbon), which is applied extensively here [6]. These analyses are fully documented and reproducible with the accompanying R code and data tables adapted from [1], and are straightforward to execute on the average desktop computer. The paper primarily presents a revision of the 14 C analysis itself and the decisions implicit therein, the reanalysis leads to the epistemological basis on which archaeological 14 C is interpreted in Amazonia to be questioned
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