New York: US researchers have found the first reliable evidence that humans played a substantial role in the extinction of Australian mega fauna -- large animal species in Australia with body mass estimates of more than 45 kilograms.
Studies have shown that more than 85 percent of Australia's mammals, birds and reptiles weighing over 100 pounds went extinct shortly after the arrival of the first humans.
Researchers from the University of Colorado Boulder in the US discovered the first direct evidence that humans were preying on the now extinct huge, wondrous beasts -- in this case a 500-pound bird.
The flightless bird, known as Genyornis newtoni, was nearly 7 feet tall and appears to have lived in much of the continent prior to the advent of humans 50,000 years ago, the study revealed.
The evidence consists of diagnostic burn patterns on Genyornis eggshell fragments that indicated that humans were collecting and cooking its eggs, thereby reducing the birds' reproductive success, the researchers said.
"We consider this the first and only secure evidence that humans were directly preying on now extinct Australian mega fauna," said Gifford Miller, professor in the University of Colorado Boulder.
The Genyornis eggs are thought to have been roughly the size of a cantaloupe - a fruit also called muskmelon, and weighed about 3.5 pounds, Miller said.
In analysing unburned Genyornis eggshells from more than 2,000 localities across Australia, primarily from sand dunes where the ancient birds nested, several dating methods helped researchers determine that none were younger than 45,000 years old.
Burned eggshell fragments from more than 200 of those sites suggested that they were exposed to a wide range of temperatures, Miller said.
It was likely that the blackened fragments were burned in transient, human fires -- presumably to cook the eggs -- rather than in wild fires, Miller explained in the paper published online in Nature Communications.
The researchers also found many of the burnt Genyornis eggshell fragments in tight clusters less than 10 feet in diameter, with no other eggshell fragments nearby.
"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 noted.
Another line of evidence for early human predation on Genyornis eggs is the presence of ancient, burned eggshells of emus -- flightless birds weighing only about 100 pounds and which still exists in Australia -- in the sand dunes.
Emu eggshells exhibiting burn patterns similar to Genyornis eggshells signalled that they were most likely scorched after humans arrived in Australia, Miller said.
The extinct mega fauna included a 1,000-pound kangaroo, a two-ton wombat, a 25-feet-long lizard, a 300-pound marsupial lion and a Volkswagen-sized tortoise.