Tuesday, 23 October 2012

Ancient Aussie Mega-Fauna Wiped Out by Early Settlers

Giant Wombats and Kangaroos Wiped out by First Settlers
The debate over the impact of human migration as humans encounter indigenous species has been fuelled once more with the publication of a new paper speculating on the demise of the mega-fauna that once lived on the island of Tasmania.
The research, carried out by a joint Australian and British team, has been published in the prestigious American scientific journal - Proceedings of the National Academy of Sciences. The research team have concluded it was the impact of human settlement and hunting that led to the extinction of many of the large animals on Tasmania, not climate change as had been previously argued.
It was the chance discovery of the remains of a giant prehistoric kangaroo that proved to be the catalyst for the study. The researchers postulate that it was the human settlers who hunted to death this slow-breeding animal and other very large mammals that lived on Tasmania at the time.
Hunting and Settlement Did for the Indigenous Prehistoric Fauna
For a long time the fauna and flora of Tasmania had been isolated from the rest of Australia but as sea levels fell a land bridge formed between this island and mainland Australia, permitting people to settle in this area. The arrival of such a proficient and capable predator such as man, would have had a major impact on the local ecosystem.
The debate regarding the significance of human settlement on the island's mega-fauna centres on the skull of a giant kangaroo found in a cave in the thick rain-forest of the rugged northwest of Tasmania eight years ago.
Scientists dated the find at 41,000 years old, some 2,000 years after humans first began to live in the area. A spokesperson for the research team commented that up until this recent research, scientists had thought that the Tasmanian mega-fauna had become extinct before modern humans arrived, but that does not seem to be the case.
Professor Roberts who led this research and his team, considering the date of the skull, had concluded that it was likely that hunting not climate change and resulted in so many extinctions. Large animals that perished around this time included the giant kangaroo, a wombat (another marsupial), the size of a cow and the fierce marsupial lions that were the top predators on the island prior to the arrival of man.
The Marsupial Lion
The marsupial lion or Thylacoleo was perhaps the largest mammalian predator of the Australian Pleistocene, it terrorised Australia until extinction approximately 40,000 years ago. Tasmania may have been one of the last places that a size-able population of these carnivores existed - although some people believe that marsupial lions still exist. There have been a number of mysterious sightings and reports of large, four-footed animals across Australia, could the Thylacoleo still exist?
Discussing the potential influence of climate change on the Tasmanian ecosystem of 40,000 years ago, Professor Roberts, acting as spokesperson for the research group stated that the idea relating sudden climate change to the extinction of many of the large animals was disputed by the fact the area had a very stable climate over this critical time period. Climatic studies had shown that the climate around Tasmania was very stable, yet many prehistoric animals become extinct. The scientists postulate that if climate change was not significant then the extinctions could have been caused due to the influence of early settlers.
Large Mammals Slow To Reproduce
Roberts said because the large animals were slow to reproduce it would not have required an aggressive campaign to see them quickly die out, however, frequent predation over a sustained period would eventually put pressure on a species to survive. The large herbivores of Tasmanian would have not encountered humans before and would not have had any natural defences or instinctive responses towards them. Animals rapidly declining in the face of a new threat is quite common amongst isolated, island populations. The Dodo for example, was wiped out in just a few years following the first human visitors to the island, there was some hunting, but rodents and dogs that arrived with the settlers were perhaps the main cause of this huge bird's demise. It was not a case of mass hunting and mass slaughter of the indigenous species. With slow-breeding animals occasional hunting with a few animals each season being killed could have been enough to set a species into terminal decline.
Man Responsible for the Demise of Mega-Fauna
Professor Roberts said the Tasmanian results back up the theory that man was responsible for the death of the mega-fauna on mainland Australia, estimated by some to have occurred shortly after human occupation about 46,000 years ago.
The reasons behind the mass extinction of giant animals, which took place around the world towards the end of the last Ice Age, has been hotly contested with theories ranging from climate change to human and extraterrestrial impacts.
The finding of the latest study has already been contested, with Judith Field of the University of Sydney saying the idea that humans killed the giant creatures was "in the realms of speculative fantasy".
Some other palaeontologists contest the findings, stating that humans had not reached Tasmania in enough numbers to significantly affect the mega-fauna.
Debate is Set to Continue
It is likely that the debate over the impact of human arrival and settlement on other species will continue. H. sapiens
in various parts of the world and at various times, may have had a significant impact on habitats and ecosystems. Whether it is the debate over the effect of Clovis man in North America, or the influence of the Cro-Magnons over European fauna, scientists will continue to theorise over the actual significance of a human population over the rest of the ecosystem. Certainly, there is no doubt that today, humans are having an enormous impact on the planet's other inhabitants. At 6.7 billion we are the most common large mammal on Earth and our exploitation of resources and demands for food and living space are having a serious impact on virtually ever other species. Indeed, some scientists have claimed that this is the period of the "sixth great mass extinction" of the Phanerozoic (visible life), with an estimated 50 species a day becoming extinct.
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