Megafauna Extinctions in Ancient Australia
In an effort to discover the connections in Australia’s past between climate change, the vanishing of the large Ice Age animals (megafauna) there, and the arrival of humans, Gifford Miller turned to fossil eggshells he found in dune deposits along the ancient shoreline of a now vanished lake. The eggshells had been left by emus, ostrich- like flightless birds that still walk Australia’s savannas and woodlands, and by Genyornis newtoni , an extinct bird species whose massive bones suggest each individual would have weighed about 550 pounds. Australia’s acid soils and severe climate quickly leach all organic matter out of bone. But because eggshells have a different mineral structure than bone, the ancient shells retained traces of protein. This made it possible to date them using a technique called amino acid racemization. Results from a large set of samples- -1,200 dates collected from three different sites- -showed that the emu and Genyornis had coexisted for millennia. Then, about 45,000 50,000 years ago, Genyornis vanished.
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