There’s been a breakthrough in the 50,000-year-old Great Egg Controversy, as scientists have finally cracked the identity of a six-foot bird that laid eggs eaten by Australia’s first people. The extinct megafauna Genyornis was to thank for the ancient humans’ feast, from the group of birds called the dromornithids or mihirungs which – thanks to their relatedness to waterfowl and enormous size – are also known as the “demon ducks of doom.”

Genyornis, also going by the name “Thunder Bird,” stood at two meters (six feet) with long legs and surprisingly stubby wings. It’s thought these birds strutted around Australia in flocks – and though a six-foot demon duck is quite an intimidating prospect, they were probably vegetarians.

Instead, it was we humans who were doing the eating, as was suspected after burned fragments of ancient eggshells were discovered several years ago. However, the discovery of the shells sparked debate as to which bird laid the eggs our ancestors were eating.

Why did it matter? Because the answer could indicate whether humans had a guilty part to play in the extinction of one of the suspects: Genyornis, who in earlier research was suspected to be the egg layer.

A second extinct bird – Progura, or “giant malleefowl” – was also floated as a contender for the egg layer after research indicated that the burned shells’ shapes and thickness made it a more likely candidate than Genyornis. These birds were more comparable to a turkey, weighing around five to seven kilograms (11 to 15 pounds).

Fossilized egg shells were all the authors of a new paper published in Proceedings of the National Academy of Sciences had to work from in order to discern between the two, but fortunately, these ancient calcium carbonate chick cases have fared quite well over the past 50,000 years.

“Time, temperature and the chemistry of a fossil all dictate how much information we can glean,” said senior co-author Prof Matthew Collins from the University of Cambridge’s Department of Archaeology in a statement.

“Eggshells are made of mineral crystals that can tightly trap some proteins, preserving this biological data in the harshest of environments – potentially for millions of years.” 

While there was no genetic material on the shells to work with, the researchers were able to extract proteins from the ancient eggshells and compare them to those of living species. This comparison revealed that whoever laid the eggs evolved before Progura emerged, pointing to Genyornis instead.

 As for how our ancestors may have tipped the species over the edge and into extinction, it seems thievery rather than butchery was likely to blame.

“There is no evidence of Genyornis butchery in the archaeological record. However, eggshell fragments with unique burn patterns consistent with human activity have been found at different places across the continent,” said senior co-author Prof Gifford Miller from the University of Colorado.

“This implies that the first humans did not necessarily hunt these enormous birds, but did routinely raid nests and steal their giant eggs for food. Overexploitation of the eggs by humans may well have contributed to Genyornis extinction.”

Whoops.