Well Mr. H. Some of us know what happend to 'Megafauna'.
From your abc
abc.net.au/science
Why did they die out?
In the last 1.64 million years several ice ages swept the world which made the world very dry. Extremely so in fact, and the seas were very low. The driest period in Australia was about 20,000 years ago Australia - even drier than it is now. Animals from many groups of backboned animals became very large but then died out or became extinct. Aborigines came to Australia at least 40,000 years ago - many scientists believe it could be earlier. So they would have been here when the last of the Megabeasts were still plodding around.
Over many thousands of years, Australia as a land has completely changed. So has the climate and the weather.
The Early Cainozoic climate, beginning approximately 65 million years ago, was completely different than it is today.
During the Time of Dinosaurs
During the late Jurassic to mid-Cretaceous Period the Australian continent was covered with shallow seas. Probably because the high, humid temperatures (possibly as high as 10degrees Celsius higher than our own!) which existed when the dinosaurs ruled the world. The glaciers had melted and the seas had risen accordingly creating a hot humid existence. Perfect for cold-blooded reptiles. Plesiosaurs swam in the warm shallow seas of central Australia.
145.6 - 65 million years ago. During the Cretaceous period Australia was hot and basically separated up into a number of landmasses separated by great shallow seas. That is why many of Australia's dinosaurs were sea-living beasts like Plesiosaurs and Ichthyosaurs.
65 - 23.3 million years ago. The forests were more temperate and water still covered much of the country with lakes and rivers. Great lush forests fed and protected large numbers of animals that were dependent on it for food and shelter. Where desert and arid conditions exist now the country might have looked more like today's tropical Queensland rainforest.
About 23 million years ago Australia broke away from Antarctica and moved northwards. It was during this last 23 million years that Australia gained all its tropical plants and animals. During the last 5 million its arid centre developed. Rainfall giving way top Spinifex grasses.
12 -15 million years ago the Australian Plate collided with the Pacific plate near New Guinea causing a great deal of pushing, shoving and general mountain building in New Guinea.
Animals and plants were able to migrate from the north to Australia which had been isolated so long. By the end of the cretaceous the earth's climate was beginning to cool once again and Australia was once again closer to the Antarctic Circle. The Antarctic was a lot milder than it is today but soon all that was to change. Ice was beginning to form at the poles again. Water was taken from the seas and cold currents disrupted previously warm marine feeding grounds. The world was still warm but a lot drier than it had been before.
During the last 1.64 million years the lush forests gave way to the grasses, which opened out the now drier continent. Animals which thrived in the forests or only ate leaves were disadvantaged by those that took to eating grasses. Fish stocks in the seas probably dwindled as the seas cooled, and the large dominant birds declined. The polar icecaps grew, water decreased and the land began to look like it does now. The central Australian lakes dried up and at about 20,000 years ago the country was even drier and dustier than it is now.
