Delayed demographic transition following the adoption of cultivated plants in the eastern La Plata Basin and Atlantic coast, South America.

Abstract

Understanding past population dynamics in lowland South America relative to changes in subsistence is crucial for drawing comparisons with global processes. Here, we use aggregated radiocarbon data as a palaeodemography proxy for in the eastern La Plata Basin and adjacent Atlantic coast, southeastern South America. Our results show that population dynamics in the study area are best explained by a three-phase model consisting of exponential growth ~6000-4000 cal BP, linear decrease ~4000-2000 cal BP and further exponential growth ~2000-500 cal BP. Local deviations from the regional trend show a heterogeneous landscape, with the first phase of exponential growth mainly driven by activity in the coast. Although the first adoption of domesticated plants occurs during that period, a causal relationship with population growth cannot be established, as plant cultivation may have been incorporated into the economy of already large and settled populations approaching carrying capacity. The second phase of exponential growth follows the arrival of new cultural traditions, bringing with them a more diverse package of cultivated plants and landscape management practises. Our results highlight the complexity of the relationships between population dynamics and changes in economy in South America, with a delayed transition attested in our study region.