SYDNEY, March 23 (UPI) -- Human hunting caused the extinction of ancient giant animals, or "megafauna," in Australia about 40,000 years ago, scientists say.

A study has put the blame for the extinction of 600-pound kangaroos and birds twice the size of modern emus on humans rather than on climate change as was once thought, Britain's The Daily Telegraph reported Friday.


"The debate really should be over now," John Alroy, from Macquarie University in Sydney, said. "Hunting did it, end of story."

The researchers studied fungi found in the dung of large herbivores in cores of sediment from a fossilized swamp in Queensland dating back 130,000 years.

"When there was lots of fungus, there was lots of dung and lots of big animals making it," Chris Johnson from the University of Tasmania said. "When they disappeared, their dung fungus went too."

The study shows numbers of megafauna species were stable until 40,000 years ago despite two periods of climate change, the researchers said, suggesting newly arrived humans hunted the animals to extinction.

Still, some scientists say they're not convinced and that the presence of the ancient spores does not reflect an abundance of the giant animals.

"The only evidence we have from Queensland for megafauna indicates that they were gone before humans arrived," Judith Field, from the University of New South Wales, said.

"The interpretations drawn from [the new study] are unsubstantiated and can be explained by other mechanisms."