Did pre-Columbian populations of the Amazonian biome reach carrying capacity during the Late Holocene?

Abstract

The Late Holocene archaeological record of the South American tropical lowlands (the Amazon basin, the Orinoco basin, and the Guianas) provides evidence of major biome-scale cultural and technological transitions. Accompanying changes in population size and density however, are often estimated on the basis of unreliable assumptions and guesswork. Drawing on recent developments in the aggregate analysis of large radiocarbon databases, here we present and examine multiple proxies for relative population change between 1000 BC and AD 1500. With a robust model-testing approach, we investigate both biome-wide and local palaeodemographic parameters of interest. Our analysis a) documents overall adhesion to a logistical model of demographic growth over the 1,700 years prior to European colonisation, b) detects a possible demographic ceiling in pre-Columbian times and, c) observe considerable variability when this signal is projected geographically. Our results, therefore, provide important demographic insights to reframe current understandings of Late Holocene demic expansion, language diversification, and subsistence intensification in the Amazon biome. Our simulation-based palaeodemographic approach, employing the most complete database of 14C data, stands to scaffold future enquiry into links between demographic and palaeoclimatic patterns in South America.