A long-running Australian detective story. Beginning in the 1980s, researchers found fragments of eggshells, and rarely whole eggs, in the eroding sand dunes of the country’s arid region (which covers most of Australia’s landmass).
Some of the shells matched ostrich-laying eggs, but the rest belonged to a mysterious species. Researchers initially determined that the eggshells belonged to an extinct giant bird. genyornis. More recently, however, a group of scientists has challenged this view.
With the help of AI software, our team has now resolved this scientific debate, showing that: genyornis indeed, it was the bird that laid the eggs. Together with our colleagues around the world, we have published the findings in Proceedings of the National Academy of Sciences.
genyornis was a flightless bird between two meters and 2.5 meters long that once roamed the Australian landmass. Eggshell fragments are an important set of evidence about this extinct creature, so it’s vital to be sure of the identity of the bird that laid them.
Some of the shell fragments are 400,000 years old, with the youngest about 50,000 years old. Previous work showed that some of the youngest eggshells burned, but not in the way a wildfire would. Instead, scientific tests show that people cook eggs for food.
The time period genyornis The disappearance of the shells (50,000 years ago) coincides with what is thought to be the first arrival of humans in Australia. The discovery therefore raises the possibility that it contributed to the extinction of our species.
Narrowing the candidates
Eggshell fragments were first noticed in 1981 by Dom Williams, a geologist and vertebrate paleontologist at Flinders University in Adelaide. genyornisbelonged to a group of extinct creatures known as thunderbirds.
In the 1990s, a team including John Magee of the Australian National University and one of the authors of this paper, Gifford Miller, gave precise dates for similar shell fragments collected at thousands of dryland areas. genyornis It was one of many large animals known as “megafauna” that once roamed Australia and disappeared around the same time. The study by Miller, Magee and others pinpointed this extinction event 50,000 years ago.
Relationship with eggshell genyornis It was widely accepted from the 1980s until recently, when a team of scientists from Flinders University in Australia objected. Based on the size and structure of their eggshells, they argued for a different parent. He was their favorite candidate programAn extinct 10 kg relative of modern birds such as the bush turkey and the malleefowl.
Living birds belonging to this group, known as megapods, build earthen mounds to incubate their eggs. Scientific debate was held in academic journals and neither side agreed.
in pursuit of a solution
Thinking that the eggs belonged to Genyornis, scientists turned to DNA to find a solution. Despite the successful extraction of genetic information from eggs of New Zealand’s extinct Moa, the latest DNA sequencing technology has left a loophole. The molecules deteriorated a lot after 50,000 years under the hot Australian sun.
However, proteins, the molecular building blocks of cells, can provide similar information and outlast DNA. In our study, we used a technique called amino acid racemization to identify shell fragments with the best conserved proteins.
As part of the study, our team was able to obtain partial protein sequences from Australian eggshells. We then used software called AlphaFold from DeepMind, the AI lab owned by Google, to create predicted structures for molecules – this is the first time it’s been done for ancient proteins.
The two of us, Matthew Collins and Beatrice Demarchi, contacted the Bird 10,000 Genomes (B10K) Project. This set the ambitious goal of sequencing the genomes of all bird species.
B10K project member Josefin Stiller took the reconstructed protein sequences and placed them in a “family tree” showing how proteins differ between bird species. The proteins were complete enough to unravel the location of the mysterious eggs within the deep branches of this protein sequence tree, but not diagnostic enough to uniquely identify what the parent bird was.
However, as detailed in our recent article, protein sequences were able to definitively rule out that the parent was a megapod. Since there were no other candidate birds, we concluded that the eggshells were avian, as Williams first suggested in the 1980s. genyornis.
This means we can safely interpret other evidence locked in shells with inferences about how to do it. genyornis became extinct, and why did the ostrich that lived next to it survive?
Isotopes are different forms of chemical elements that can record information about factors such as diet and climate. The carbon isotopes in the eggshell fragments inform and indicate the diet of the birds. genyornis He was a more picky eater than an emu. Oxygen isotopes can be used to monitor drought and show that conditions are getting progressively drier over time. genyornis egg shells disappear.
In previous work, Miller and colleagues analyzed the same isotopes in emu eggshells. Genyornis’ extinction and found that summertime grasses were suddenly disappearing from the birds’ diets. This is consistent with the dramatic reduction in monsoon rains.
These findings show that genyornis it was already somewhat vulnerable to a changing environment, but another factor may have proven to be important to its eventual fate.
coupled with the lack of evidence genyornis Skeletons for direct predation, burnt eggshells, as is so common elsewhere in the world, suggest that human pressure may have been a factor driving these impressive birds finally to extinction.
This article has been republished under a Creative Commons license from The Conversation. Read the original article.
Matthew James Collins receives funding from the Danish National Research Foundation. It is affiliated with the University of Copenhagen.
Beatrice Demarchi receives funding from the Italian Ministry of University and Research
Gifford Miller receives funding from the US National Science Foundation.