Alan N. Williams

A new population curve for prehistoric Australia

This paper presents a new reconstruction of prehistoric population of Australia for the last 50 ka, using the most comprehensive radiocarbon database currently available for the continent. The application of new techniques to manipulate radiocarbon data (including correction for taphonomic bias), gives greater reliability to the reconstructed population curve. This shows low populations through the Late Pleistocene, before a slow stepwise increase in population beginning during the Holocene transition (approx. 12 ka) and continuing in pulses (approx. 8.3–6.6, 4.4–3.7 and 1.6–0.4 ka) through the Holocene. These data give no support for an early saturation of the continent, although the estimated population following initial landfall was probably greater than previously allowed (comparable with the Early Holocene). The greatest increase in population occurred in the Late Holocene, but in contrast to existing intensification models, changes in demography and diversification of economic activities began much earlier. Some demographic changes appear to be in response to major climatic events, most notably during the last glacial maximum, where the curve suggests that population fell by about 60 per cent between 21 and 18 ka. An application of statistical demographic methods to Australian ethnographic and genetic data suggests that a founding group of 1000–2000 at 50 ka would result in a population high of approximately 1.2 million at approximately 0.5 ka. Data suggests an 8 per cent decline to approximately 770 000–1.1 million at the time of European contact, giving a figure consistent with ethnographic estimates and with historical observations of the impact of smallpox, and other diseases introduced by Macassans and Europeans during and after AD 1788.

Human—environment interactions in Australian drylands: exploratory time-series analysis of archaeological records

Exploratory time-series analysis of radiocarbon data from archaeological contexts is used to reconstruct the population history of arid Australia, allowing this to be read in concert with records of climatic variability over the last 20 000 years. Probability distribution plots of 971 radiocarbon ages from 286 sites in five dryland regions (the arid west coast, Pilbara and Murchison, Nullarbor, arid interior and the southeastern arid zone) provide a proxy record of prehistoric population fluctuations in these areas. There is regional variation, but the radiocarbon density plots suggest a step-wise pattern of population growth and expansion, with significant thresholds at 19, 8 and 1.5 cal. kyr BP. Within this, the plots suggest a saw-tooth pattern of rapid population growth and decline on a 1—3 kyr frequency, with a marked collapse of dryland hunter-gatherer populations around 3—2.5 cal. kyr BP affecting most regions. Comparison with climate data shows broad correlations with past temperature and rainfall variability, sea-level change and ENSO activity, but the interaction of prehistoric populations and these environmental changes is not well resolved. High amplitude environmental changes appear to have triggered stadial changes in population, rather than smooth transitions. Dryland populations may also have become more sensitive to small environmental changes in the late Holocene, as population density increased. A large increase in population around 1.5 cal. kyr BP is associated with small changes in regional palaeoecology, which are not otherwise represented in palaeoclimatic data sets. Spectral analysis identifies two cyclical periodicities of 1340 and 175 years within the population histories, also suggesting responses to millennial and submillennial climatic variability, a pattern most marked in the late Holocene.

THE IMPACT OF ENSO IN THE ATACAMA DESERT AND AUSTRALIAN ARID ZONE: EXPLORATORY TIME-SERIES ANALYSIS OF ARCHAEOLOGICAL RECORDS

La comparacion de datos arqueologicos del desierto de Atacama y de la zona arida de Australia muestra el impacto de El Nino-Oscilacion del Sur en los ultimos 5.000 anos. Con base en un listado de > 1.400 dataciones radiocarbonicas de ambas regiones, utilizadas como fuente indirecta de fluctuaciones de la poblacion, se realizaron graficos de densidad de las dataciones para explorar las respuestas de las poblaciones prehistoricas a las variaciones climaticas provocadas por ENSO. Bajo un regimen ENSO las precipitaciones se encuentran en antefase entre Australia y la costa del norte de Chile. Dado que ENSO impacta en la productividad de los recursos marinos y suprime el ingreso de humedad de la cuenca del Amazonas, su efecto en las economias de subsistencia de ambos lados del Pacifico Tropical deberia correlacionarse positivamente. Esto se confirma a traves de analisis cruzados de espectros de graficos de densidad de radiocarbonos, lo que muestra fluctuaciones sincronicas de la poblacion en ambos lados del Pacifico Tropical (r = > 0,82). Las bases de datos de Australia y del desierto de Atacama muestran un aumento gradual de la poblacion desde los 13 mil cal anos a.p., y un incremento importante durante el optimo climatico del Holoceno medio. La intensificacion de ENSO a partir de los 3,7 cal anos a.p. se correlaciona con ciclos de florecimiento y declinacion de la ocupacion humana en ambos lados del Pacifico, incluyendo el colapso del sistema economico y cultural en la costa del desierto de Atacama alrededor de 3 mil anos cal a.p. y la declinacion de la poblacion en las zonas interiores aridas del Atacama y del centro de Australia, entre 3-2 mil anos cal a.p. Posterior a 2 mil anos cal a.p. las respuestas adaptativas varian entre ambas regiones, aunque se produce una recuperacion general de las poblaciones en sus zonas aridas interiores.

Excavations at Parnkupirti, Lake Gregory, Great Sandy Desert: OSL Ages for Occupation Before the Last Glacial Maximum

Abstract We report on early occupation from the Parnkupirti site on Salt Pan Creek at Lake Gregory, on the edge of the Great Sandy Desert of northwest Australia. OSL ages from excavations, and stratigraphic correlations between dated exposures along Salt Pan Creek, show some stone artefacts in situ in sediments dating from greater than 37ka and most probably on stratigraphic grounds in the range of ~50–45ka. The deep stratigraphic section at Parnkupirti also provides a long record of the Quaternary history of Lake Gregory, which remained a freshwater system during the Late Quaternary.

Holocene Demographic Changes and the Emergence of Complex Societies in Prehistoric Australia

A continental-scale model of Holocene Australian hunter-gatherer demography and mobility is generated using radiocarbon data and geospatial techniques. Results show a delayed expansion and settlement of much of Australia following the termination of the late Pleistocene until after 9,000 years ago (or 9ka). The onset of the Holocene climatic optimum (9-6ka) coincides with rapid expansion, growth and establishment of regional populations across ~75% of Australia, including much of the arid zone. This diffusion from isolated Pleistocene refugia provides a mechanism for the synchronous spread of pan-continental archaeological and linguistic attributes at this time (e.g. Pama-Nyungan language, Panaramitee art style, backed artefacts). We argue longer patch residence times were possible at the end of the optimum, resulting in a shift to more sedentary lifestyles and establishment of low-level food production in some parts of the continent. The onset of El Niño - Southern Oscillation (ENSO; 4.5-2ka) restricted low-level food production, and resulted in population fragmentation, abandonment of marginal areas, and reduction in ranging territory of ~26%. Importantly, climate amelioration brought about by more pervasive La Niña conditions (post-2ka), resulted in an intensification of the mobility strategies and technological innovations that were developed in the early- to mid-Holocene. These changes resulted in population expansion and utilization of the entire continent. We propose that it was under these demographically packed conditions that the complex social and religious societies observed at colonial contact were formed.

Are tulas and enso linked in Australia

Abstract The distinctive tool called ‘tula’ is an endemic adaptation, which was adopted by Aboriginal people across central and western Australia, encompassing some two-thirds of the continent. The tula is a hafted tool used for working hardwoods as well as other tasks including butchery and plant-processing. The geographic spread of tulas appears to have been rapid and no antecedent form has been identified. The sudden appearance of tulas was coincident with the onset of El Niño Southern Oscillation (ENSO) conditions. While we do not yet have the data to establish an unequivocal causal link, in this paper we hypothesise that the appearance of this new and specialised tool at c.3700 BP was very likely a human response to the intensification of ENSO. This intensification resulted in increased aridity and climatic variability lasting almost 2000 years. We posit that this technological adaptation, an element of a risk minimisation toolkit, was part of a wider economic and social strategy adopted by Aboriginal people to cope with increasing climatic uncertainty. This possibility has implications for the diversity of innovation processes operating in Australia during the Holocene, which is further explored in this paper with concluding suggestions for future research. We offer this discussion as a platform for these future, and what we believe, are very necessary critical studies.

Aboriginal mitogenomes reveal 50,000 years of regionalism in Australia

Aboriginal Australians represent one of the longest continuous cultural complexes known. Archaeological evidence indicates that Australia and New Guinea were initially settled approximately 50 thousand years ago (ka); however, little is known about the processes underlying the enormous linguistic and phenotypic diversity within Australia. Here we report 111 mitochondrial genomes (mitogenomes) from historical Aboriginal Australian hair samples, whose origins enable us to reconstruct Australian phylogeographic history before European settlement. Marked geographic patterns and deep splits across the major mitochondrial haplogroups imply that the settlement of Australia comprised a single, rapid migration along the east and west coasts that reached southern Australia by 49–45 ka. After continent-wide colonization, strong regional patterns developed and these have survived despite substantial climatic and cultural change during the late Pleistocene and Holocene epochs. Remarkably, we find evidence for the continuous presence of populations in discrete geographic areas dating back to around 50 ka, in agreement with the notable Aboriginal Australian cultural attachment to their country.

Holocene environmental changes in the Lower Thames Valley, London, UK: Implications for understanding the history of Taxus woodland

A radiocarbon-dated multiproxy palaeoenvironmental record from the Lower Thames Valley at Hornchurch Marshes has provided a reconstruction of the timing and nature of vegetation succession against a background of Holocene climate change, relative sea level movement and human activities. The investigation recorded widespread peat formation between c. 6300 and 3900 cal. yr BP (marine ‘regression’), succeeded by evidence for marine incursion. The multiproxy analyses of these sediments, comprising pollen, Coleoptera, diatoms, and plant and wood macrofossils, have indicated significant changes in both the wetland and dryland environment, including the establishment of Alnus (Alder) carr woodland, and the decline of both Ulmus (Elm; c. 5740 cal. yr BP) and Tilia (Lime; c. 5600 cal. yr BP, and 4160–3710 cal. yr BP). The beetle faunas from the peat also suggest a thermal climate similar to that of the present day. At c. 4900 cal. yr BP, Taxus (L.; Yew) woodland colonised the peatland forming a plant community that has no known modern analogue in the UK. The precise reason, or reasons, for this event remain unclear, although changes in peatland hydrology seem most likely. The growth of Taxus on peatland not only has considerable importance for our knowledge of the vegetation history of southeast England, and NW Europe generally, but also has wider implications for the interpretation of Holocene palaeobotanical records. At c. 3900 cal. yr BP, Taxus declined on the peatland surface during a period of major hydrological change (marine incursion), an event also strongly associated with the decline of dryland woodland taxa, including Tilia and Quercus, and the appearance of anthropogenic indicators.

A terminal pleistocene open site on the Hawkesbury River, Pitt town, New South Wales

Abstract Salvage excavations of 25 m2 on a levee adjacent to the Hawkesbury River near Pitt Town, New South Wales, identified a 1.5 m deep sand body containing three discrete artefact assemblages, collectively designated as site PT12. Six optically stimulated luminescence (OSL) ages provide a chronology for the sand body, which began forming >50 ka. Peak artefact numbers for the two lowest assemblages were centred on ca 15 ka and ca 11 ka, and had Capertian (pre-Bondaian) characteristics. These included amorphous pebble tools and manuports of locally-derived river cobbles, which were probably exposed through entrenchment of the river during lower sea-levels. Comparisons with the KII rockshelter, approximately 20 km upstream, show a similar assemblage dated to ca 13 ka. The uppermost assemblage at PT12 was dominated by backed artefacts and composed primarily of silcrete. Reliable OSL ages indicate this assemblage may have been deposited in the early Holocene, with a proliferation of backed blades occurring ca 5 ka, although typological comparisons with other local assemblages suggest an age of < 4.5 ka is more likely. Along with other studies, the site indicates the systematic exploitation of resources along the Hawkesbury River from ca 15 ka before an apparent abandonment of the region in the early/mid-Holocene. Late Holocene artefact numbers suggest a subdued reoccupation of the area following this hiatus.

Puntutjarpa rockshelter revisited: a chronological and stratigraphic reappraisal of a key archaeological sequence for the Western Desert, Australia

Abstract Puntutjarpa Rockshelter was the first archaeological site excavated in the Australian desert. Dug between 1967 and 1970, the archaeological sequence was originally interpreted as a continuous record spanning the last 10,000 years BP. With a new series of radiocarbon and OSL dates we show that Puntutjarpa primarily contains a mid-Holocene deposit with a veneer of last millennium material and a thin underlay of terminal Pleistocene evidence. We show that over the last 12.0 kyr, there were three discrete phases of site-use at Puntutjarpa – 12.0–9.7 kyr, 8.3–6.2 kyr and ∼1.1–0 kyr – each with differences in the nature and intensity of occupation. This removes key field evidence for the ‘Australian Desert Culture’, a concept that has increasingly become an anomaly since the 1980s.