A new study involving ancient poop revealed that the arrival of human, and not climate change, is most likely the primary cause of the sharp dive in the population of the Australian Megafauna some 45,000 years ago.

The study, published in the journal Nature Communications, showed that the Australian Megafauna is abundant some 150,000 years ago to about 45,000 years ago. However, their population went extinct shortly after the arrival of first humans.

"The results of this study are of significant interest across the archaeological and Earth science communities and to the general public who remain fascinated by the menagerie of now extinct giant animals that roamed the planet -- and the cause of their extinction - as our own species began its persistent colonization of Earth," said lead author Sander van der Kaars, of Monash University, in a press release.

For the study, search for the presence of spores from a fungus called Sporormiella, which thrived on the dung of plant-eating mammals, in the sediment core drilled off the coast of southwest Australia. Aside from fungal spores, the researchers also analyzed the dust, pollen and ash in the sediment core to chronologically reconstruct the past climate and ecosystems of the continent.

The researchers found that the fungal spores were abundant in the sediment core layers from 150,000 years ago. However, the amount of fungal spores starts to dwindle starting from 45,000 years ago. The earliest immigrants of Australia are believed to colonized most of the continent by 50,000 years ago.

As the humans continue to grow, they began to hunt the large animals to their extinction. A previous study showed that even a low-intensity hunting, or killing one juvenile animal per person per decade, could lead to the extinction of a species in just a few hundred years.

The Australian Megafauna is known for its collection of large and unusual animals. These include 1,000-pound kangaroos, 2-ton wombats, 25-foot-long lizards, 400-pound flightless birds, 300-pound marsupial lions and Volkswagen-sized tortoises.