Giant kangaroos, two-metre tall wombats and large flightless birds that once roamed prehistoric Australia may have been hunted into extinction, according to the latest scientific research.
It was widely thought a drying climate was responsible for the demise of Australian megafauna, which began to disappear around 40,000 years ago.
However, a new Royal Society biology paper published this week proposes that first humans wiped them out.
"We looked at all the evidence available and the dates of when humans arrived and what the climate was doing," co-author and James Cook University Professor Michael Bird told AAP.
"We found the climate wasn't doing anything it hadn't done before ... and there was a close link between humans and megafauna extinction."
It is thought humans arrived on the Sahul landmass - an unbroken continent now Papua New Guinea, Australian mainland and Tasmania - 45 to 55,000 years ago.
Prof Bird says large vertebrates started to disappear quickly around the same time.
"We're not saying people came and started killing everything," he said.
"But when people get involved in population dynamics, through things like hunting, taking eggs and killing juveniles, it affects things over time."
A study published last year found evidence of charred animal eggs, indicating they were cooked for human consumption.
It remains difficult to pinpoint a precise time frame, with carbon dating and climate records sketchy.
But Prof Bird believes early inhabitants greatly shaped the landscape of current Australia.
"The modern environment could be a big legacy of what happened around 50,000 years ago," he said.
Megafauna - animals such as the 200cm tall, wombat-like diprotodon and giant kangaroo procoptodon - existed during the Pleistocene period, from around 1.8 million years ago until their extinction.
The research paper was published in biology journal 'Proceedings of the Royal Society B' on Wednesday.
Megafauna in Australia
The giant wombat-like creature was the largest marsupial to have lived. It grew two metres tall, weighing almost three tonnes.
A large flightless bird, Genyornis lived from 1.8 million to 40,000 years ago in dry grassland and woodlands.
The snub-faced kangaroo was more than two metres tall and weighed around 230kg.