Thylacine Read Online Free PDF Page B

Charles Darwin’s 1859 The Origin of Species . The thylacine belongs in a third category, of human-induced extinctions, and so joins vast numbers of terrestrial, arboreal, aerial and aquatic species which have become extinct in just that way. However, it would be dangerous in the extreme to ascribe positive Darwinian notions of survival of the fittest (that humans need to eat) to justify extinction of, say, the dodo or the passenger pigeon.
    The statistics of human-induced extinctions can be mind-boggling. During the course of the nineteenth century something like 5 billion passenger pigeons were shot in the United States, along with up to 50 million Great Plains bison killed, and almost that many pronghorn antelope. Human ingenuity and cunning aside, many lost species simply lacked defence mechanisms against humans as predator. Dodos were not stupid: they simply had no inbuilt fear of people. This is a common trait among creatures endemic to remote islands where Europeans settled, such as Hawaii, New Zealand and Madagascar. Conversely, many creatures are naturally wary of man: an instinct developed over long periods of time.
    Extinction is tricky: ‘We have only the haziest idea about how many species currently exist on earth, how many there may have been in the past, and how many are going extinct at any one time’. 3
    The devastation of Australia’s Ice Age megafauna was swift and severe. Thirteen genera of large marsupial mammals—about 45 megafaunal species—perished. This had occurred by about 20 000 years ago, when humans were well-established on the continent. Were they hunted to extinction? If they were, perhaps the thylacine survived because it was comparatively small and also mostly nocturnal. The thylacine in fact belongs in a rare subcategory of human-agency extinction, since it was exterminated not as a food (nor in the name of sport) but because it was supposedly destroying an economic asset, namely, sheep.
    Can random or background extinction explain the thylacine’s disappearance from mainland Australia? This natural extinction process inevitably operates over a very long period of time and, equally inevitably, climate plays a role of some sort in it. Climate change alters growing conditions, which affect herbivores; in turn, carnivores are affected. It may be that the harshness resulting from continental Australia’s aridification, and the sheer size of the continent, dispersed the thylacine gene pool to the point where introduced packs of hunting, scavenging dingoes more effectively took over the vast ‘niche’.
    Dingoes came to Australia with the Aborigines, from regions to the north, not more than 12 000 years ago (when dingo-free Tasmania was cut off) and probably much more recently—about 6000 years ago. 4 Fossil evidence indicates that mainland thylacines were then widespread; the same evidence shows them to be extinct by about 3000 years ago. This rapid decline is of interest in itself, but is all the more intriguing for the fact that it parallels the decline of the Tasmanian devil on the mainland. Why did that strictly nocturnal, scavenging predator suffer a similar fate?
    What is certain is that there have been two quite distinct thylacine extinctions, first on mainland Australia and New Guinea, and subsequently in Tasmania. There is no evidence that wild dogs competed successfully with thylacines in Tasmania after 1803—except in a cruelly oblique way, where thylacines were incorrectly blamed for dog-kills of sheep. More questionable is whether a competitor species, introduced through human agency, constitutes a ‘natural’ form of competition. Given the thousands of years over which the dingo–thylacine struggle apparently took place, one could say that struggle was natural. But the later introduction to Australia by settlers of many animals, which soon became feral, was not, setting in motion as it did endemic extinctions, destabilising