Gigantic Australian bird Genyornis became extinct because of humans
A gigantic 7-foot tall Australian bird called Genyornis that existed about 50,000 years ago, most probably became extinct because of humans, who hunted its eggs and cooked them, a team of scientists led by the University of Colorado Boulder found.
Genyornis newtoni was a massive 500-pound (227 kg) flightless bird and used to inhabit most of Australia before humans started settling on the continent approximately fifty thousand years ago, according to Gifford Miller, Professor of Geological Sciences at CU-Boulder.
Genyornis newtoni was huge bird. An adult male ostrich, for example, weighs 264 pounds (120 kg).
Genyornis newtoni startled by a 25-foot-long, 1-ton lizard (Megalania prisca). The 6-foot-tall man is in the picture to show how large the bird was. Fifty thousand years ago, there were many huge animals in Australia. (Image: colorado.edu)
Details of the study and its findings were published in the academic journal Nature Communications.
Humans cooked Genyornis eggs
The researchers found burn patterns on Genyornis eggshell fragments, suggesting that the giant birds’ eggs were being gathered and cooked – a practice that probably undermined its reproductive success.
Prof. Miller, who is associate director of CU-Boulder’s Institute of Arctic and Alpine Research, added:
“We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian *megafauna. We have documented these characteristically burned Genyornis eggshells at more than 200 sites across the continent.”
* Megafauna refers to large animals of a particular region, habitat, or geological period.
Prof. Miller and colleagues analysed several unburned Genyornis eggs from over 2,000 locations across Australia. Most of the specimens were found in sand dunes, the ancient bird’s favourite nesting site.
Eggs were at least 45,000 years old
Several dating methods were used, which helped the scientists determine that they were all at least 45,000 years old.
Genyornis eggshell fragment blackened only at one end. (Image: Nature)
The authors said burned eggshell fragments found in more than 200 of those sites, suggested that the eggs were exposed to a wide range of temperatures.
Optically stimulated luminescence dating, a method they used to determine when the quartz grains within the eggshells were last exposed to sunlight, suggests that the eggshells come from between 54,000 and 44,000 years ago, while radiocarbon dating indicates that the burnt eggshells are at least 47,000 years old.
The darkened fragments were probably burned in transient, human fires – presumably to cook the eggs – rather than wildfires, the authors said.
Amino acids, which proteins are made of, decompose in a predictable fashion over time inside eggshells.
An artist’s impression of a the mega-large kangaroo (Procoptodon Goliah) – compared to a modern kangaroo (middle) and an adult male human – that used to exist in Australia a long time ago. Australia used to have some huge animals. (Image: kawek.com.br)
Eggs were not burnt by wildfires
In eggshell fragments where one end is burnt but not the other, there is a tell-tale ‘gradient’ from total to minimal amino acid decomposition, Prof. Miller explained.
Such a gradient is only possible if there had been a localized heat source, such as an ember, and not from the sustained high heat that one would get from wildfires, which have been common in Australia since prehistory.
The researchers also found several of the burnt eggshell fragments in tight clusters within a 10-foot diameter, with no other eggshell fragments nearby.
Some eggshell fragments from the same clusters had heat gradient differences of almost 1,000 °F (538 °C) – such conditions are virtually impossible to reproduce with natural wildfires, Prof. Miller commented.
Australian postage stamp (2008) of Genyornis. (Image: paleophilatelie.eu)
Prof. Miller said:
“We can’t come up with a scenario that a wildfire could produce those tremendous gradients in heat. We instead argue that the conditions are consistent with early humans harvesting Genyornis eggs, cooking them over fires, and then randomly discarding the eggshell fragments in and around their cooking fires.”
Emu eggs were also cooked
Another line of evidence of ancient humans preying on Genyornis eggs is the presence of prehistoric, burned eggshells of emus – much lighter flightless birds (100 lbs) and which still exist today in Australia – in the sand dunes.
Emu eggshells that had been burned in a similar way to Genyornis eggshells first appeared on the Australian landscape about 50,000 years ago, suggesting they probably were scorched after humans arrived in Australia, and are found fairly consistent to modern times, the authors wrote.
The Genyornis eggs are thought to have weighed about 3.5 pounds (1.59 kg) and were approximately the size of a cantaloupe melon, Prof. Miller said.
When Genyornis existed, so did many other now-extinct huge creatures, including:
– a giant 1,000-pound (454 kg) kangaroo,
– a wombat weighing two tons,
– a 300-pound (136 kg) marsupial lion,
– a tortoise the size of a Volkswagen beetle, and,
– a 25-foot-long lizard.
Much megafauna died off after humans arrived
Not long after the first humans arrived, over 85% of Australia’s mammals, birds and reptiles weighing in excess of 100 pounds (45 kg) went extinct.
Scientists have long argued about the demise of ancient megafauna in Australia, North America and other continents. Some say human predation was the cause, others point to climate change, and a significant number believe it could have been due to a combination of both.
While some scientists are convinced that climate change was the cause – specifically the continental drying in Australia from about 60,000 to 40,000 years ago – neither the rate nor scale of that change was as severe as the earlier climate shifts in the region during the Pleistocene epoch, which had no significant impact on the fate of the megafauna.
Prof. Miller and colleagues believe Australia’s first human inhabitants arrived at the northern coast of the continent on rafts from Indonesian islands several hundred miles away.
Prof. Miller said:
“We will never know the exact time window humans arrived on the continent. But there is reliable evidence they were widely dispersed across the continent before 47,000 years ago.”
Finding evidence of megafauna hunting in Australia is much harder than in the New World. Partly because of the chemistry of Australian soils, which destroys them, and also because the megafauna in Australia is much older.
Prof. Miller said:
“In the Americas, early human predation on the giant animals in clear — stone spear heads are found embedded in mammoth bones, for example.”
“The lack of clear evidence regarding human predation on the Australia megafauna had, until now, been used to suggest no human-megafauna interactions occurred, despite evidence that most of the giant animals still roamed Australia when humans colonized the continent.”
Study co-authors include doctoral student Christopher Florian, Research Professor Scott Lehman, and researcher DeVogel of CU-Boulder; Research Fellow John Magee of ANU (Australian National University); and scientists from seven other Australian institutions.
The study was funded in part by the Australian Research Council and the US National Science Foundation.
Citation: “Human predation contributed to the extinction of the Australian megafaunal bird Genyornis newtoni ~47 ka,” Gifford Miller, Harvey Johnston, Doug Williams, John Magee, Mike Smith, Nigel Spooner, Alexander Baynes, Stephen DeVogel, Scott Lehman, Marilyn Fogel, Peter Clark, Richard Holst & Christopher Florian. Nature Communications 7, Article number: 10496. Published 29 January 2016. DOI: 10.1038/ncomms10496.
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