COEXISTENCE OF HUMANS AND MEGAFAUNA IN AUSTRALIA

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COEXISTENCE OF HUMANS AND MEGAFAUNA IN AUSTRALIA



Troublesome Questions
In 1830 Mr. Rankin tied a rope around a projection out of a rock face in order to lower himself into Wellington Cave (Horton, 1980). The projection turned out to be the bone of a giant extinct marsupial. It was to be the first discovery of a great range of giant marsupials. Were these animals extinct?? Horton (1980), describes how Leichhart believed that on his journeys to northern Australia he would find Diprotodon still roaming over the land. We now know that he was probably only about 20,000 years to late (Flood, 1995). In general, all the animals greater than 40 kg in body weight became extinct at the end of the last Ice Age. By the mid 19th century scientists had already begun to postulate about the disappearance of these animals, and today it remains one of the most controversial subjects presented to man, (Horton, 1980).
Australia was not the only country to experience extinctions of large animals, (Martin, 1984). At the end of the last glacial period nearly every continent experienced extinctions of large animals. Animals like the Mammoth, giant ground sloths, and mastodons were roaming the Americas. Northern Eurasia featured woolly mammoths, giant deer, hippopotamus and straight tusked elephants. Of all the continents, it could be argued that Australia lost some of the most distinctly unique fauna in the world. The popular opinion for the cause of extinction is the 'blitzkrieg' hypothesis, which is held by such researches as Paul Martin in his controversial article "Prehistoric Overkill: The Global Model". This states that humans are directly responsible for these extinctions world wide. The Problem with this model for Australia is that humans may have arrived on this continent well before the extinctions took place (Flood, 1995). On other continents the extinctions coincided almost exactly with the arrival of man (Martin, 1984).
European man was not the first member of the genus Homo to set foot on the Australian continent. There is evidence to suggest that Aboriginal people have been walking on Australian soil for many tens of thousands of years (Flood, 1995). Whether or not Aboriginal people interacted with the large now extinct beasts is hard to determine. Did an overlap in time exist between humans and these large beasts? Is there any evidence that humans actively hunted them, and if they did, is it possible that they drove them to extinction?

Land of the Giants
During the late Pleistocene, the last glacial period spanning roughly 100,000 years, the faunas were completely different to those that are represented today. The most pronounced difference is body size. The term 'megafauna', meaning 'large animals' has been used to describe late Pleistocene animals throughout the world. We know that most species of mammals greater than 60 kg in bodyweight became extinct at the end of the Pleistocene. 'Megafauna' is not a taxonomic group nor is there a standard definition. Generally, the term megafauna describes an animal that weighs 40 kg or more, but in Australia that would result in including four species of living kangaroos (the grey, red, antilopine and wallaroo) and probably excluding the extinct carnivore Thylacoleo and the smaller Sthenurus (short faced kangaroo) (Murray, 1991 in Vickers-Rich et al., 1991). Horton, (1984) came up with a tedious but more precise definition for the Australian megafauna: 'Animals that became extinct before the Holocene and are large, either in an absolute sense or relative to other members of some taxonomic rank, or are part of a taxonomic category all of whose members became extinct and some of whose members are large.'
Fifteen genera and roughly forty-one species of mammalian megafauna became extinct in Australia at the end of the Pleistocene (Flannery, 1990). It should be noted that this essay is not going to consider the many large birds (e.g. Genyornis) and reptiles (e.g. Megalania prisca) which also became extinct during the Late Pleistocene. If these non-mammals are added to the tally of extinctions, the number of megafaunal genera extinct goes up to nineteen (Flood, 1990).
A typical mammalian megafaunal community consisted of a variety of forms, such as: Zaglossus; Marsupial Lion Thylacoleo; giant wombats Phascolonus; long-beaked echidnas; the Marsupial Tapir (Palorchestidae); Diprotodon (Diprotodontidae); and some especially large morphs of the living Macropus (Macropodidae), (Murray, 1991 in Vickers-Rich et al., 1991). The most deserving of the term 'megafauna', was Diprotodon, which probably looked like a wombat 'gone wrong'. Weighing in at 2000 kg, Diprotodon was a browser which preferred the drier open expanses of the interior of Australia. The majority of the megafauna was herbivorous, such as the cow sized Zygomaturus trilobus, the stumpy giant wombat Phascolonus gigas, and the large macropods Procoptodon, and Protemnodon. A trend seen in the megafaunal assemblage, that still exists with the extant fauna today, is the distinct lack of carnivores (Flood, 1990). The Pleistocene carnivores were limited to just three species: Thylacoleo carnifex, known as the 'Marsupial lion' or the 'giant killer possum'; the carnivorous lizard Megalania; and the Tasmanian 'tiger', Thylacines. Thus, the large herbivores of Australia did not co-evolve with a fleet of carnivores, like hyenas and canids and felids of Africa. Flannery, (1994) believes it is the lack of carnivores that led to faunas dominated by lumbering beasts that weren't fast long distance runners like those found in Africa. Flannery also suggested that being slow and naive to predators, was a factor that led to their demise.
One of the most frustrating aspects of palaeontology is trying to place a fossil bearing rock into the geological record. It wasn't until 1945 when radiocarbon dating was first applied in Australia, that the pieces of the megafaunal puzzle started to fit together (Horton, 1980). Since then, dating techniques have improved. However, there are still problems with dating bone so palaeontologists have had to rely on stratigraphic association using more reliable, datable materials such as charcoal and shell (Flood, 1990). Bone samples lose their collagen with time, and are also susceptible to contamination, especially by younger calcium carbonate carried down by groundwater. It is for these reasons that the exact timing of the extinction of the megafauna is controversial.
There are many Late Pleistocene fossil sites found within Australia (Fig Martin last of the aus meg). Of these sites, there a few that have narrowed down the timing of the extinction event to somewhere around 20,000 years ago. (Fig Flood page 183). These sites, in general, are all open sites situated in south-eastern Australia (Flannery, 1990). Gilespie et al. (1978) describes a bone bed that contains up to '10,000 giant marsupials' at Lancefield Swamp in Victoria. The megafauna has been dated fairly reliably, from charcoal in sediments directly below the fossil bed, at 25,000 800 BP and 26,000 650 (Fig flood). There are other, less reliable date, which may nevertheless support late existing Pleistocene megafauna. Amongst these: Spring Creek, first dated on plant matter at 19,000 390 BP (Flannery and Gott 1985), later revised to 35,000 BP (Flood, 1994); Beginners Luck Cave, dated from bone collagen dates at 10,100 200 BP, and 1,450 210 BP (Murray and Goede, 1977, in Flannery 1990); and finally Lime Springs, NSW bone fragments have been dated at around 19,000 to 6000 BP (Flannery, 1990). If we take these dates as correct then we could have had megafauna roaming around Australia as early as 6,000 BP or even 1,450 BP. Unfortunately these are thought of as suspect. The bone from Beginners Luck Cave has been interpreted as being an example contamination, and the bone from Lime Springs is thought of by some as being reworked. The good news is that after all the controversy surrounding dates of various sites, Cuddie Springs in semi-arid New South Wales has provided sound information about the timing of extinction. Cuddie Springs provides a secure stratigraphic succession which contains abundant bones (Fig. Cuddie springs). A series of dates have been done on charcoal that range from 30,280 450 BP for the base of the succession to 19,270 320 BP for the top. This means that Megafauna definitely existed in Australia until 20,000 years ago.

Unwanted Guests
Much of the field of human palaeontology is of little relevance to understanding the history of Australia evolution (Flannery, 1994). This is because much of the evolution of man occurred on other continents such as Africa and Asia. Until this year, it was known from archaeological evidence in the Northern Territory that Aboriginal people first arrived in Australia at least 60,000 years before present (Flood, 1994). Recent evidence suggests that we may have to re-write the text books when it comes to human evolution. In mid-September of this year scientists discovered in the Kimberly region of Western Australia, several enormous sculptured boulders that had detailed circular engravings on them, (Woodford, 1996). This rock art, which has been dated at up to 75,000 years old, may be the oldest rock art in the world - more than twice the age of the French rock paintings at Chauvet and Cosquer. While excavating the sediments below the art, ochre was found dating up to 116,000 years, (Fig Sydney Morning Herald). Artefacts (stone tools) were also found in a layer of sediment between 116,000 and 176,000 years old.
During the Pleistocene there were two major drops in sea level due to huge amounts of water frozen in ice sheets. These glacial maximums occurred around 18,000 years ago, and 140,00 years ago (Flannery, 1994). This drop i

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