There are thousands of Pleistocene sites in Australia where the fragments of giant eggshells have been found. These shells often have characteristic burn marks, indicating that they have been cooked rather than scorched in the bush to burn† Dating back to about 50,000 years ago, they are thought to have been a food source for the first Australians. However, scientists have not yet been able to identify the bird species to which the eggs belonged, because the shells have spent thousands of years in the Australian heat and the DNA has broken down beyond recognition.
There were always two contenders for the bird species responsible. The first, and most likely, was genyornis, an extinct flightless bird that was more than two meters long, weighed 220-240 kg and laid eggs the size of a melon with a mass of about 1.5 kg. But some scientists have argued that, due to the shape, size and thickness of the shell, the eggs may have been laid by the giant malleefowl, progura, instead of. This extinct bird was much smaller, comparable to a large turkey and only about 5-7 kg.
The distinction is important because: Genyornis is believed to have died out just a few thousand years after the arrival of the first Australians, some 65,000 years ago. While there is no fossil evidence of places where the birds were slaughtered, the thousands of places where eggs were boiled (and presumably eaten) support the idea that humans were involved in the demise of this megafaunal species.
If, on the other hand, the eggs belonged to progurawhat is a flying bird that laid its eggs in mounds on the ground then humans would in no way be involved in the extinction of the giant Genyornis. In fact, there would be no direct evidence of human-Genyornis interaction, and it may even be possible that this species was already extinct by the time humans arrived in Australia.
An international team led by the University of Cambridge has now performed multiple analysis to identify the mysterious egg layer. The experts used the highly fragmented ancient DNA, but also extracted ancient proteins from powdered eggshells and compared the protein sequences to those of living bird species using a massive new database of biological material known as the Bird 10,000 Genomes (B10K). project .
The results indicate that the eggs were indeed laid by the extinct giant bird, Genyornis. Also known as mihirung — or “Thunder Bird,” this huge bird with tiny wings and huge legs roamed prehistoric Australia, possibly in flocks.
“There is no evidence of Genyornis butcher shop in the archaeological archive. However, eggshell fragments with unique burning patterns consistent with human activity have been found in several places on the continent,” said senior co-author Professor Gifford Miller of the University of Colorado.
This implies that the first humans did not necessarily hunt these huge birds, but routinely raided nests and stole their giant eggs for food. Over-exploitation of the eggs by humans may have contributed to: Genyornis become extinct.”
The analysis and comparison of protein sequences allowed the researchers to definitively conclude that the eggshells did not belong to any species of the Magapodiidae, such as progura† The researchers were also able to construct an evolutionary tree using the protein sequences of other extinct and extant birds in closely related groups, and identify the position of the egg layer in relation to other bird taxa.
“The progura was related to today’s megapods, a group of birds in the galliform lineage, which also includes ground feeders such as chickens and turkeys,” said the study’s lead author, Professor Beatrice Demarchi of the University of Turin.
“We found that the bird responsible for the mysterious eggs emerged before the galliform lineage, giving us the… progura hypothesis. This supports the implication that the eggs eaten by early Australians were laid by Genyornis†
The study confirms that using the sequences of ancient proteins is a powerful tool to reconstruct the evolutionary history of ancient organisms and clarify their phylogenetic positions. Proteins from the ancient eggshells were a reliable source of information in a situation where DNA analysis did not yield conclusive results.
“Time, temperature and the chemistry of a fossil all determine how much information we can collect,” said study co-author Professor Matthew Collins of the Department of Archeology at the University of Cambridge. “Eggshells are made of mineral crystals that can tightly lock in some proteins, preserving this biological data in the harshest of environments — possibly for millions of years.”
The researchers point out that the Genyornis The egg-exploitation behavior of the early Australians likely mirrors that of early humans with ostrich eggs, whose shells have been unearthed at archaeological sites across Africa that are at least 100,000 years old.
“While ostriches and humans coexisted in prehistoric times, the extent of exploitation of Genyornis eggs from early Australians may have ultimately proved more than the reproductive strategies of these extraordinary birds could tolerate,” said Professor Collins.
The study is published in the journal Proceedings of the National Academy of Sciences†
Image credit: Peter Trusler
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