Try 50,000:
"An international team of researchers, including a UK collaboration led by BBSRC- and MRC-funded researchers at Imperial College London, with colleagues at University College London, and University of Cambridge has for the first time sequenced the genome of a man who was an Aboriginal Australian. They have shown that modern day Aboriginal Australians are the direct descendents of the first people who arrived on the continent some 50,000 years ago and that those ancestors left Africa earlier than their European and Asian counterparts."
Aboriginal Australians descend from the first humans to leave Africa, DNA sequence reveals
It seems that you will make up any number you want.
Of course you won't.
The age of the origins of humans in Australia is hotly debated by the experts, but skeletal remains like those at Lake Mungo in New South Wales, by Jim Bowler in February 1974, have been dated between 15,000 and 50,000 years old.
Australia's fossil past | australia.gov.au
The marsupials were already in Australia for tens of millions of years before the Aboriginees got there. That is what the fossil record shows.
Any animals that were there before the flood were destroyed by the flood. That would include any marsupials that were there.
Also, there is no reason that they would not bring placental mammals with them, like placental rabbits. Also, what they would take with them is not determined by the millions of years of fossils already buried in Australia.
Why not?
Then why don't we see that on other continents?
In a series of new genetic investigations, experts demonstrate that kangaroos and other marsupials did not evolve in Antarctica, as previously thought. It would appear that the animals actually appeared in South America, and that they still exist there today. Marsupials stand out from other species through the fact that they feed and carry their youngsters around in special pouches on their bellies. With the new finding, experts are bound to gather even more data on the history of this family of creatures.
In order to make the research possible, scientists looked at the marsupial species that still live in South America today. The two recently sequenced marsupial genomes of the South American opossum (Monodelphis domestica) and a kangaroo, the Australian tammar wallaby (Macropus eugenii), provide a unique opportunity to apply a completely new approach to resolve marsupial relationships, explains researcher Maria A. Nilsson. She is based at the University of Munster, in Germany, LiveScience reports.
Nilsson is also the leader of an international group of experts that conducted the new investigation. The group published its findings in the July 27 issue of the esteemed open-access journal PLoS Biology, which is edited by the Public Library of Science. The group reveals that studies highlight a very interesting point all marsupials living today, in both South American and Australia share a common ancestor. The conclusion was derived from analysis of special genetic markers called retroposons, which are identical in marsupials on both continents.
However, determining the history of this animal group for a fact is very difficult, given that no hard evidence exist. Researchers would be ecstatic to find a fossil of an intermediary creature, but thus far such a finding has eluded them. The genetic data seems to indicate that the species currently in existence as well as some that have since gone extinct separate from a common ancestor around 80 million years ago. At that time, the landmass that contained Antarctica, Australia and South America broke apart, and the three new continents began drifting on Earth's mantle.
Kangaroos Come from South America
