Burn marks discovered on the 50,000-year-old eggshell fragments several years ago suggested the first Australians cooked and ate large eggs from extinct birds, leading to fierce debate over the species that laid them. According to a new analysis of ancient protein sequences from the eggshell, the ancient eggs came from Genyornis, a giant flightless ‘mihirung’ that became extinct between 30,000 and 5,000 years ago.
Fossil records show that Genyornis stood over 2 m tall, weighed between 220-240 kg, and laid melon-sized eggs of around 1.5 kg.
It was among the Australian megafauna to vanish a few thousand years after humans arrived, suggesting people played a role in its extinction.
The earliest robust date for the arrival of humans to Australia is some 65,000 years ago.
“There is no evidence of Genyornis butchery in the archaeological record,” said Professor Gifford Miller, a researcher in the Institute of Arctic and Alpine Research and the Department of Geological Sciences at the University of Colorado, Boulder.
“However, eggshell fragments with unique burn patterns consistent with human activity have been found at different places across the continent.”
“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.”
While Genyornis was always a contender for the mystery egg-layer, some scientists argued that a more likely candidate was Progura, another extinct bird, much smaller, weighing around 5-7 kg and akin to a large turkey.
The initial ambition was to put the debate to bed by pulling ancient DNA from pieces of shell, but genetic material had not sufficiently survived the hot Australian climate.
Professor Miller and colleagues were able to compare the sequences in ancient proteins to those of living species using a vast new database of biological material: the Bird 10,000 Genomes (B10K) project.
“Progura was related to today’s megapodes, a group of birds in the galliform lineage, which also contains ground-feeders such as chickens and turkeys,” said Professor Beatrice Demarchi, a researcher in the Department of Life Sciences and Systems Biology at the University of Turin.
“We found that the bird responsible for the mystery eggs emerged prior to the galliform lineage, enabling us to rule out the Progura hypothesis.”
“This supports the implication that the eggs eaten by early Australians were laid by Genyornis.”
The researchers point out that the Genyornis egg exploitation behavior of the first Australians likely mirrors that of early humans with ostrich eggs, the shells of which have been unearthed at archaeological sites across Africa dating back at least 100,000 years.
“While ostriches and humans have co-existed throughout prehistory, the levels of exploitation of Genyornis eggs by early Australians may have ultimately proved more than the reproductive strategies of these extraordinary birds could bear,” said Professor Matthew Collins, a researcher in the Department of Archaeology at the University of Cambridge.
The findings appear in the Proceedings of the National Academy of Sciences.
Beatrice Demarchi et al. Ancient proteins resolve controversy over the identity of Genyornis eggshell. PNAS, in press; doi: 10.1073/pnas.2109326119
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