At some point, about 60 large native vertebrate species died out on the continent, and until now, no one could confirm when or why this happened. A new study, by geologist Gifford Miller and colleagues, applies several dating techniques to pinpoint the extinction date of one large vertebrate from the continent. Genyornis newtoni was a large, emu- like bird. While the emu survived, the authors suggest that Genyornis's clumsy features may have contributed to its extinction. Miller and his coworkers analyzed fossilized Genyornis eggshells from several sites across Australia.
Eggshells store and preserve amino acids particularly well.
While alive, almost all creatures incorporate amino acids with a left- handed geometry into their tissues. In addition, they also used carbon-14 dating and a similar technique that relies on the radioactive decay of uranium atoms. Finally, a fourth analysis gauged the radioactivity of sand grains in which the eggshells were embedded, which gave another estimate for the fossils' ages. The combination of all these techniques points to an extinction date for Genyornis between 45,000 and 55,000 years ago. That timeframe matches the best estimate for when people arrived in Australia from Indonesia.