It was made of pollen, dust, and spores from a fungus that used to grow on the dung of some of the herbivore megafauna - all organised in chronological layers.
Miller, who helped at developing the study led by Sander van der Kaars of Monash University, stated that the primary sediment helped scientists travel back in time, being able to analyze data about ancient animals.
Researchers analysed a precisely dated sediment core collected offshore in southwest Australia, which provided evidence for the last 150,000 years, Science News said. He also argued that these spores' abundance represents evidence of the fact that many large species of mammals on the southwestern Australian area have lived up until 45,000 years ago. There were also 25-foot-long lizards that looked right out of a sci-fi movie, and marsupial lions and tortoises the size of a auto were also decimated in just a few hundred years. These terrifyingly impressive megafauna roamed the Australasian continent for thousands of years before swiftly disappearing.
UC Boulder Prof. Gifford Miller said in a statement, "Because of the density of trees and shrubs, it could have been one of their last holdouts some 45,000 years ago".
A study in Proceedings of the National Academy of Sciences in 2013 said Australia's giant animals were already mostly extinct by the time humans arrived - and pointed the finger at climate change.
But researchers have found that shortly after humans arrived in Australia, more than 85 per cent of these megafauna went extinct.
Around 45,000 years ago, numerous unique megafauna species that thrived in Australia disappeared.
In fact, earlier studies have pinned the extinction of the huge animals on climate change, with one theory suggesting that weather events that started 70,000 years ago transformed southwestern Australia's landscape from a wooded environment rich with eucalyptus trees to a dry landscape with little vegetation. The majority of experts claim the animals died because of climate changes. So humans, and their relentless march across the world, were the most likely cause.
In North America they stretched over Greenland and Canada and parts of the northern United States.
There was a lot of movement over time, and there were about 20 cycles when the glaciers would advance and retreat as they thawed and refroze.
The name Pleistocene is the combination of two Greek words: pleistos (meaning "most") and kainos (meaning "new" or "recent").
A 2006 study by Australian researchers indicates that even low-intensity hunting of Australian megafauna - like the killing of one juvenile mammal per person per decade - could have resulted in the extinction of a species in just a few hundred years. A 2015 study looked at the drying lakes in central Australia as evidence that the loss of water resources contributed to the disappearance of the megafauna.
A study published this week in Nature Communications suggests Australia's giant animals went extinct over just a few thousand years-which is fast for well-established species like this.