What happened at 1500—1000 cal. BP in Central Australia? Timing,impact and archaeological signatures

This paper reviews the late Holocene archaeology of Central Australia. The last 1500 years saw significant changes in the archaeological record in this part of the Australian arid zone, with shifts in settlement pattern, site histories, resource use, tool inventories and rock art. Much of the evidence points to regional population growth, beginning 1500—1000 cal. BP and coinciding with expansion of summer-rainfall grassland and more frequent palaeoflood events. Hunter-gatherer groups appear to have increased their use of marginal or outlying areas as these became seasonally accessible. Responses to the demographic changes, especially in the better-watered ranges, include more extended occupation of existing sites, more processing of acacia and grass seeds, and an increase in territoriality reflected in the greater differentiation of rock art complexes after 1500 cal. BP. The archaeological changes are not scaled commensurately with the modest environmental shifts at this time, indicating that human—environment interactions were not linear. A human—environment threshold may have been breached 1500—1000 years ago, with existing socio-economic or historical factors acting to amplify the effects of small environmental changes. However, it remains difficult to fully characterize the nature of these human—environment interactions, despite the fine-grained archaeological record now available. An unresolved problem for this emerging picture of climatic amelioration and population growth is that Aboriginal settlement in Central Australia was expanding at a time when ENSO-driven variability appears to have been at its highest.