Abstract
The mechanisms leading to megafauna (>44 kg) extinctions in Late Pleistocene (126,000—12,000 years ago) Australia are highly contested because standard chronological analyses rely on scarce data of varying quality and ignore spatial complexity. Relevant archaeological and palaeontological records are most often also biased by differential preservation resulting in under-representated older events. Chronological analyses have attributed megafaunal extinctions to climate change, humans, or a combination of the two, but rarely consider spatial variation in extinction patterns, initial human appearance trajectories, and palaeoclimate change together. Here we develop a statistical approach to infer spatio-temporal trajectories of megafauna extirpations (local extinctions) and initial human appearance in south-eastern Australia. We identify a combined climate-human effect on regional extirpation patterns suggesting that small, mobile Aboriginal populations potentially needed access to drinkable water to survive arid ecosystems, but were simultaneously constrained by climate-dependent net landscape primary productivity. Thus, the co-drivers of megafauna extirpations were themselves constrained by the spatial distribution of climate-dependent water sources.
Highlights
The mechanisms leading to megafauna (>44 kg) extinctions in Late Pleistocene (126,000— 12,000 years ago) Australia are highly contested because standard chronological analyses rely on scarce data of varying quality and ignore spatial complexity
We overcome these methodological limitations by developing and applying a statistical approach to the available data describing megafauna extirpations and patterns of human appearance in south-eastern Australia over the last 120,000 years to test three explicit hypotheses: (1) megafauna extirpations followed changing climate conditions, (2) megafauna extirpations followed the arrival of Aboriginal populations in the region, or (3) megafauna extirpations followed a combination of both climate change and human arrival
We show that (i) >80% of south-eastern Australia had a period of humanmegafauna coexistence lasting from 1000 to >15,000 years, and (ii) the pattern of megafauna extirpation in these areas is best explained by an additive effect of the patterns of human spread and freshwater availability across the region
Summary
The mechanisms leading to megafauna (>44 kg) extinctions in Late Pleistocene (126,000— 12,000 years ago) Australia are highly contested because standard chronological analyses rely on scarce data of varying quality and ignore spatial complexity. 14) are either not spatially explicit and disregard spatial variation in extinction patterns, initial human appearance trajectories, and palaeoclimate change[7,15], or they generate new spatial biases via arbitrary geographic binning[8,9,10] or spatially continuous estimation[16] that do not account for the uncertainty arising from sampling and taphonomic biases[17], inherent dating errors[18], or spatial biases generated when interpolating a linear chronology from unevenly spaced age estimates We overcome these methodological limitations by developing and applying a statistical approach to the available data describing megafauna extirpations and patterns of human appearance in south-eastern Australia over the last 120,000 years to test three explicit hypotheses: (1) megafauna extirpations followed changing climate conditions, (2) megafauna extirpations followed the arrival of Aboriginal populations in the region, or (3) megafauna extirpations followed a combination of both climate change and human arrival. These findings suggest that only by adding spatial complexity into standard chronological analyses can we explicitly identify both humans and climate change as the most likely drivers of these extinctions
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