Prehistory of Australia - Advent of Fire Farming and Megafauna Extinctions

Advent of Fire Farming and Megafauna Extinctions

Archaeological evidence (in the form of charcoal) indicates that fire, already a growing part of the Australian landscape, became much more frequent as hunter-gatherers used it as a tool to drive game, to produce a green flush of new growth to attract animals, and to open up impenetrable forest. Densely grown areas became more open sclerophyll forest, open forest became grassland. Fire-tolerant species became predominant: in particular, eucalyptus, acacia, and grasses.

The changes to the fauna were even more dramatic: the megafauna, species significantly larger than humans, disappeared, and many of the smaller species were wiped out too. All told, about 60 different vertebrates became extinct, including the Diprotodon family (very large marsupial herbivores that looked rather like hippos), several large flightless birds, carnivorous kangaroos, a five metre lizard and Meiolania, a tortoise the size of a small car.

The direct cause of the mass extinctions is uncertain: it may have been fire, hunting, climate change or a combination of all or any of these factors, although the rapid decline of many species means the once popular climate change explanation is no longer favoured. With no large herbivores to keep the understorey vegetation down and rapidly recycle soil nutrients with their dung, fuel build-up became more rapid and fires burned hotter, further changing the landscape.

The period from 18,000 to 15,000 years ago saw increased aridity of the continent with lower temperatures and less rainfall than currently prevails. Between 16,000 and 14,000 years BP the rate of sea level rise was most rapid rising about 50 feet in 300 years according to Peter D. Ward. At the end of the Pleistocene, roughly 13,000 years ago, the Torres Strait connection, the Bassian Plain between modern-day Victoria and Tasmania, and the link from Kangaroo Island began disappearing under the rising sea.

From that time on, the Tasmanian Aborigines were geographically isolated. By 9,000 years ago small islands in Bass Strait, as well as Kangaroo Island were no longer inhabited.

Linguistic and genetic evidence shows that there has been long-term contact between Australians in the far north and the Austronesian people of modern-day New Guinea and the islands, but that this appears to have been mostly trade with a little intermarriage, as opposed to direct colonisation. Macassan praus are also recorded in the Aboriginal stories from Broome to the Gulf of Carpentaria, and there were some semi-permanent settlements established, and cases of Aboriginal settlers finding a home in Indonesia.