Reconstructing the dynamics of ancient human populations from radiocarbon dates: 10 000 years of population growth in Australia

Abstract

Measuring trends in the size of prehistoric populations is fundamental to our understanding of the demography of ancient people and their responses to environmental change. Archaeologists commonly use the temporal distribution of radiocarbon dates to reconstruct population trends, but this can give a false picture of population growth because of the loss of evidence from older sites. We demonstrate a method for quantifying this bias, and we use it to test for population growth through the Holocene of Australia. We used model simulations to show how turnover of site occupation across an archaeological landscape, interacting with erasure of evidence at abandoned sites, can create an increase in apparent site occupation towards the present when occupation density is actually constant. By estimating the probabilities of abandonment and erasure from archaeological data, we then used the model to show that this effect does not account for the observed increase in occupation through the Holocene in Australia. This is best explained by population growth, which was low for the first part of the Holocene but accelerated about 5000 years ago. Our results provide new evidence for the dynamism of non-agricultural populations through the Holocene.

Agriculture, population growth, and statistical analysis of the radiocarbon record

“…Fig. 3 shows measurements of the annual growth rate calculated from SPDs for North America (26), Australia (27), and Europe (28). The SPD comparison is restricted to studies that report measurements of the long-term growth rate.…”

“…The growth rate calculated from these data are significant because the methodology used to estimate the population size is completely independent from our analysis and therefore provides an important cross-check on the systematic uncertainties of the SPD approach. Many studies have indicated that SPDs are valid demographic proxies (25)(26)(27)(28)(29)(30)33). Fig.…”

“…Radiocarbon dates provide a direct record of prehistoric human activity, and large samples have been used for quantitative demographic analysis (25)(26)(27)(28)(29)(30). Larger populations produce more datable material; thus, the temporal frequency of the radiocarbon record reflects the size of the population.…”

A new population curve for prehistoric Australia

“…Time-series radiocarbon data is widely used as a proxy for human activity or prehistoric population [13,17,25,[31][32][33][34]. Analysis and interpretation of this form of data is complex and has several limitations ([24]; see the electronic supplementary material).…”

Dating the Anthropocene: Towards an empirical global history of human transformation of the terrestrial biosphere

“…Observations from the field Archaeological and paleoecological evidence already confirm that humans have a long history of altering ecosystems at sites around the world beginning in the late Pleistocene (Smith and Zeder, 2013;Braje and Erlandson, 2013;Ellis et al, 2013). Site data are also being used to reconstruct population and land use histories at increasingly larger scales and levels of detail Johnson and Brook, 2011;Gaillard et al, 2010;Dincauze, 2000;Shennan et al, 2013). Nevertheless, it is clear that land-use histories and impacts of regional environments varied greatly across contemporaneous regions, which calls for more detailed local and regional studies and methods of integrating them across global scales.…”