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Prehistoric Bird Eaten to Extinction By Early Humans

Jan 29, 2016 12:53 PM EST

A 500-pound, flightless Australian bird was hunted to extinction by humans 50,000 years ago, researchers from the University of Colorado Boulder reveal in a new study. This find represents the first direct evidence suggesting humans played a substantial role in the extinction of early Australian animals.

In this case, the victim was a flightless seven-foot-tall bird, scientifically known as Genyornis newtoni. Evidence of burn patterns were found on Genyornis eggshell fragments, indicating early humans were collecting and cooking its eggs -- each of which were about the size of a cantaloupe and weighed about 3.5 pounds, according to a news release.

"We consider this the first and only secure evidence that humans were directly preying on now-extinct Australian megafauna," Gifford Miller, the associate director of CU-Boulder's Institute of Arctic and Alpine Research, said in the release. "We have documented these characteristically burned Genyornis eggshells at more than 200 sites across the continent."

Many of the burnt Genyornis eggshell fragments were found in tight clusters less than 10 feet in diameter, with no other eggshell fragments nearby. While some of the fragments were only partially blackened, others had severe burns, suggesting the fragments were exposed to a wide range of temperatures.  For instance, the blackened fragments were likely burned in transient, human fires - perhaps to cook and eat them - while others had heat gradient differences of nearly 1,000 degrees Fahrenheit - conditions virtually impossible to reproduce with natural wildfires there.

Amino acids, the building blocks of proteins, decompose in a predictable fashion inside eggshells over time. Therefore, researchers were able to infer what heat source the egg was exposed to.

"In eggshell fragments burned at one end but not the other, there is a tell-tale 'gradient' from total amino acid decomposition to minimal amino acid decomposition," Miller added. "Such a gradient could only be produced by a localized heat source, likely an ember, and not from the sustained high heat produced regularly by wildfires on the continent both in the distant past and today."

Researchers, however, are unable to come up with a scenario if how ancient wildfires would have produced such tremendous gradients of 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," Miller continued.

Providing support to their theory is nearly identical fire-toasted emu eggshell fragments dating to the same period found at other Australian sites.

 Emus, also a flightless bird, can still be found in Australia today. However, they are much smaller than Genyornis was; they weigh only about 100 pounds.

In addition to emus and humans, Genyornis roamed the Australian outback with many other now-extinct megafauna. This included a 1,000-pound kangaroo, a two-ton wombat, a 25-foot-long-lizard, a 300-pound marsupial lion and a Volkswagen-sized tortoise.

However, all of these large animals were no match for humans - nearly 85 percent of Australia's mammals, birds and reptiles weighing over 100 pounds went extinct shortly after the arrival of the first humans.

It is believed that Australia's first inhabitants traveled to the northern coast of the continent on rafts launched from Indonesian islands several hundred miles away.

"We will never know the exact time window humans arrived on the continent," Miller said. "But there is reliable evidence they were widely dispersed across the continent before 47,000 years ago."

This find, recently published in the journal Nature Communications, is truly a remarkable one for Australia, as fossil evidence is easily destroyed by the chemistry of the continent's soils.

"In the Americas, early human predation on the giant animals in clear - stone spear heads are found embedded in mammoth bones, for example," Miller concluded in the release. "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."

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