Groundbreaking genetic research reveals Aboriginal Australians and New Guineans descend from two distinct groups who settled the ancient supercontinent of Sahul 60,000 years ago.

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There is no relationship between the demographic susceptibility to extinction and the estimated extinction chronology among Sahul’s megafauna, suggesting that human choices, a species’ ecological requirements, and/or random climate variation instead determined the extinction chronology.

There is no relationship between the demographic susceptibility to extinction and the estimated extinction chronology among Sahul’s megafauna, suggesting that human choices, a species’ ecological requirements, and/or random climate variation instead determined the extinction chronology.

There is no relationship between the demographic susceptibility to extinction and the estimated extinction chronology among Sahul’s megafauna, suggesting that human choices, a species’ ecological requirements, and/or random climate variation instead determined the extinction chronology.

Extinctions stemming from environmental change often trigger trophic cascades and coextinctions. However, it remains unclear whether trophic cascades were a large contributor to the megafauna extinctions that swept across several continents in the Late Pleistocene. The pathways to megafauna extinctions are particularly unclear for Sahul (landmass comprising Australia and New Guinea), where extinctions happened earlier than on other continents. We investigated the role of bottom-up trophic cascades in Late Pleistocene Sahul by constructing pre-extinction (~ 80 ka) trophic network models of the vertebrate community of Naracoorte, south-eastern Australia. These models allowed us to predict vertebrate species’ vulnerability to cascading extinctions based on their position in the network. We tested whether the observed extinctions could be explained by bottom-up cascades, or if they should be attributed to other external causes. Species that disappeared from the community were more vulnerable, overall, to bottom-up cascades than were species that survived. The position of extinct species in the network – having few or no predators – also suggests they might have been particularly vulnerable to a new predator. These results provide quantitative evidence that trophic cascades and naivety to predators could have contributed to the megafauna extinction event in Sahul. ### Competing Interest Statement The authors have declared no competing interest.

Design Type(s) data integration objective • species comparison design Measurement Type(s) Vertebrate Taxonomy • fossil age • geographic location Technology Type(s) data item extraction from journal article Factor Type(s) Sample Characteristic(s) megafauna • Australasian Region Machine-accessible metadata file describing the reported data (ISA-Tab format)

Design Type(s) data integration objective • species comparison design Measurement Type(s) Vertebrate Taxonomy • fossil age • geographic location Technology Type(s) data item extraction from journal article Factor Type(s) Sample Characteristic(s) megafauna • Australasian Region Machine-accessible metadata file describing the reported data (ISA-Tab format)