The changing abundance of backed artefacts in south-eastern Australia: a response to Holocene climate change?

The timing of the introduction, proliferation and decline of backed artefacts in Australia has been much debated. In south-eastern Australia, after initially appearing at least 8500 years ago, backed artefacts greatly increased in number between 4000 and 3500 years ago to the extent that they are found in numerous sites and are recorded in large numbers in individual sites from that time. From about 1500 years ago they declined markedly in number and had seemingly disappeared by the time of British colonization. Models explaining their proliferation advance the proposition that increased backed artefact production was triggered by heightened foraging risk and/or social re-organisation brought about by a change in climate to a regime which was cooler and drier than any other time during the Holocene combined with intensified ENSO climatic conditions. Our study develops this hypothesis by inferring the use of backed artefacts at Mussel Shelter in the Sydney Basin through an integrated use-wear and residue analysis. These inferences provide new insights into the nature of the evolutionary changes in tool production and use in response to the period of altered climatic conditions.