50,000 years ago, a 500-pound flightless bird, Genyornis newtoni, roamed the Australian outback. According to a report from the Washington Post, scientists from the University of Colorado at Boulder have made a strong case that humans may have been responsible for the eventual extinction of the massive birds.

Megafauna once ruled the world, and scientists believe that it wasn’t until humans showed up that things started to change. According to CU-Boulder professor Gifford Miller, early human ancestors played a key role in the extinction of Genyornis newtoni. Evidence shows that our ancestors had a taste for eggs by the time they inhabited Australia.

“We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian megafauna,” said Miller. “We have documented these characteristically burned Genyornis newtoni eggshells at more than 200 sites across the continent.”

So how did Miller and his research team pin the disappearance of Genyornis newtoni on human beings? The scientists analyzed unburned eggshells from over 2,000 sites across the continent. Most of the samples were discovered in the dunes where the birds made their nests.

They then used multiple dating methods to try and determine the age of the eggshell samples. They were surprised to learn that none of the Genyornis newtoni eggshells discovered in Australia were younger than 45,000 years old. In addition, a number of the samples examined did have burn marks, suggesting that the eggs were exposed to higher than normal temperatures.

So have humans been making omelets since the hunter-gatherer days? The evidence suggests that this is the most likely explanation for the disappearance of Genyornis newtoni. Scientists analyzed the remaining amino acids in the eggshell fragments, which decompose at a predictable rate over time. From a burned edge of a fragment to an unburned edge, an amino acid gradient suggested that the burn marks were produced by a localized heat source, and not a wildfire.

A press release from the University of Colorado at Boulder describing the recent study’s details can be found here.