Abstract
Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. Here we present a continuous 150,000-year record offshore south-western Australia and identify the timing of two critical late Pleistocene events: wide-scale ecosystem change and regional megafaunal population collapse. We establish that substantial changes in vegetation and fire regime occurred ∼70,000 years ago under a climate much drier than today. We record high levels of the dung fungus Sporormiella, a proxy for herbivore biomass, from 150,000 to 45,000 years ago, then a marked decline indicating megafaunal population collapse, from 45,000 to 43,100 years ago, placing the extinctions within 4,000 years of human dispersal across Australia. These findings rule out climate change, and implicate humans, as the primary extinction cause.
Highlights
Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago
Nowhere is the issue more acute than in Australia, where 85% of the continent’s large mammal species went extinct sometime shortly after 50 kyr ago[9,10,14,15], approximately the same time that humans established their first firm presence around the continent[14,16]. Dating both human colonisation and megafaunal extinction in Australia has been hampered by the occurrence of both events at or beyond the reliable limits of radiocarbon dating[15,17,18,19]
The region has some of the earliest evidence for human arrival on the continent[19,24] and is a candidate refugium for large mammals during past periods of aridity[25], making it an ideal location to explore the response of megafauna to climate changes and human activity
Summary
Environmental histories that span the last full glacial cycle and are representative of regional change in Australia are scarce, hampering assessment of environmental change preceding and concurrent with human dispersal on the continent ca. 47,000 years ago. We present a continuous, stratigraphically well-constrained 150,000-year multi-proxy record from a sediment core recovered B100 km offshore south-western Australia, in which we identify the timing and sequence of events of the most widespread and sustained regional ecosystem changes over the past 150,000 years and precisely date regional megafaunal extinction.
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