Ancient extinction of giant Australian bird points to humans

First reliable evidence humans were preying on now-extinct Australian Megafauna

Date:January 29, 2016

Source:University of Colorado at Boulder

The first direct evidence that humans played a substantial role in the extinction of the huge, wondrous beasts inhabiting Australia some 50,000 years ago -- in this case a 500-pound bird -- has been discovered by a University of Colorado Boulder-led team.

The flightless bird, known as Genyornis newtoni, was nearly 7 feet tall and appears to have lived in much of Australia prior to the establishment of humans on the continent 50,000 years ago, said CU-Boulder Professor Gifford Miller. The evidence consists of diagnostic burn patterns on Genyornis eggshell fragments that indicate humans were collecting and cooking its eggs, thereby reducing the birds' reproductive success.

"We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian megafauna," said Miller, associate director of CU-Boulder's Institute of Arctic and Alpine Research. "We have documented these characteristically burned Genyornis eggshells at more than 200 sites across the continent."

A paper on the subject appears online Jan. 29, in Nature Communications.

In analyzing unburned Genyornis eggshells from more than 2,000 localities across Australia, primarily from sand dunes where the ancient birds nested, several dating methods helped researchers determine that none were younger than about 45,000 years old. Burned eggshell fragments from more than 200 of those sites, some only partially blackened, suggest pieces were exposed to a wide range of temperatures, said Miller, a professor in CU-Boulder's Department of Geological Sciences.

Optically stimulated luminescence dating, a method used to determine when quartz grains enclosing the eggshells were last exposed to sunlight, limits the time range of burned Genyorniseggshell to between 54,000 and 44,000 years ago. Radiocarbon dating indicated the burnt eggshell was no younger than about 47,000 years old.

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