Some prehistoric animals included a bird three times the size of an ostrich and a burrowing animal as big as an elephant. Others included a kangaroo three metres tall. Such creatures were all Australian megafauna, alive during the Pleistocene. (A period 2.6 million-10,000 years ago)

Fifteen million years ago, 55 species of megafauna were widespread in Australia, the largest of which was the marsupial diprotodon, weighing around 2700 kilograms (5952 lb). Giant snakes, crocodiles, and birds were also common. Wombats and kangaroos reached more than 200 kg (440 lb), and even koalas weighed 16 kg (35 lb). Then, rather suddenly, around 46 thousand years ago (46 kyr), all these animals became extinct. Some scientists claim this was due to environmental pressures, like climate change or fire; others favour predation.

At the end of the Pleistocene, humans reached Australia via Indonesia, and, according to the archaeological record, by 45 kyr their settlement was widespread. One hundred and sixty archaeological sites in Australia and New Guinea have been studied in detail. There is some disagreement about the dates of these sites, and one group of researchers aims to push human settlement back before 45 kyr. Dating the rare bones of megafauna was highly controversial until 20 years ago, when a technique called optically stimulated luminescence (OSL) was developed. With OSL, the age of minerals up to 200 kyr can be established with +/- 10% accuracy.

The largest OSL dating of megafauna was carried out in 2001 by Roberts, who placed the extinction date for megafauna at around 46 kyr, very early in the period of human habitation.