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In broad usage, the Holocene extinction event includes the remarkable disappearance of large Mammal s, known as Megafauna , by the end of the Last Ice Age 9,000 to 13,000 years ago. Such disappearances have been considered as either a response to climate change, a result of the proliferation of Modern Human s, or both. These extinctions, occurring near the Pleistocene / Holocene boundary, are sometimes referred to as the Pleistocene extinction event or Ice Age extinction event. The observed rate of extinction has risen dramatically in the last 50 years, to a rate which appears to be similar to, or perhaps greater than, the rate seen during the Big Five. There is no general agreement on whether to consider more recent extinctions as a distinct event or merely part of a single escalating process. Only during these most recent parts of the extinction have Plant s also suffered large losses. Overall, the Holocene extinction event is most significantly characterised by the presence of man-made driving factors and its very short Geological Timescale (tens to thousands of years) compared to most other extinction events. THE PREHISTORIC EXTINCTION EVENTS The ongoing extinction event seems more outstanding if we follow tradition and separate the recent extinction (approximately since the Industrial Revolution ) from the Pleistocene extinction near the end of the last Ice Age . In Popular Imagination the latter is exemplified by the extinction of the woolly Mammoth and, incorrectly, the Neanderthal people. However, modern Climatology suggests the current Holocene epoch is no more than the latest in a series of Interglacial intervals between Glaciation events, perhaps one that will be artificially extended by Global Warming . Furthermore, there is a continuum of extinctions between 13,000 years ago and now. If only considering human impact, the vulnerability and extinction rate of species simply rises with the rise of technology, so there would be no need to separate the Pleistocene extinction from the recent one. Nevertheless, the Pleistocene extinction event is large enough and hasn't been resolved completely. The Pleistocene or Ice Age extinction event The Ice Age extinction event is characterised by the extinction of many large mammals weighing more than 40 kg. In North America around 33 of 45 Genera of large mammals went extinct, in South America 46 of 58, in Australia 15 of 16, in Europe 7 of 23, and in Subsaharan Africa only 2 of 44. The South American extinction witnessed the aftermath of the Great American Interchange . Only in South America and Australia did the extinction occur at family-levels or higher. There are two main hypotheses concerning this extinction:
The prehistoric overkill hypothesis is not universally applicable and is imperfectly confirmed. For instance, the timing of sudden extinctions of Marsupial Australian Megafauna and a giant Lizard , which followed the arrival of human beings in Australia by many thousands of years, need examining. Biologists note that comparable extinctions have not occurred in Africa , where the fauna evolved with hominids. Post-glacial megafaunal extinctions in Africa have been spaced over a longer interval. An alternative to the theory of human responsibility is Alexander Tollmann's Bolide Theory , a more controversial hypothesis which claims that the Holocene was initiated by an Extinction Event caused by Bolide impacts. Major megafaunal extinctions =Europe (circa 15,000 years ago) =Mediterranean Islands (by 9000 years ago)
=North America Circa 12,000-9000 years BP, 35 to 40 species of large mammals, while only about half a dozen small mammals, disappeared. Previous North American extinction pulses had occurred at the end of glaciations, but not with such an imbalance between large mammals and small ones. The megafaunal extinctions include twelve genera of edible grazers (G), and five large, dangerous carnivores ('''C'''). North American extinctions included
The survivors are as significant as the losses: Bison , Moose (recent immigrants through Beringia ), Wapiti ( Elk ), Caribou , Deer , Pronghorn, Muskox, Bighorn Sheep, Mountain Goat. All save the Pronghorns descended from Asian ancestors that had accommodated with human predators. This connection has recently been expanded upon and supported in detail by R. D. E. MacPhee, ''Extinctions in Neartime,'' 1999, an outgrowth of an American Museum Of Natural History conference on extinctions, 1997. The culture that has been connected with the wave of extinctions in North America is the paleo-Indian culture associated with the Clovis People (''q.v.''), who were thought to use Spear Thrower s to kill large animals. The chief opposition to the "prehistoric overkill hypothesis" has been that population of humans such as the Clovis culture were too small to be ecologically significant. Other generalized evocations of climate change fail under detailed scrutiny. According to Jared Diamond 's '' Guns, Germs, And Steel '', the lack of Tameable megafauna was one of the reasons why Amerindian Civilization s developed at a slower rate than Old World ones. Critics have disputed this by arguing that, with Llama , Vicuña , and Bison , there was no such lack. Reference : E. C. Pielou, ''After the Ice Age: the return of life to glaciated North America,'' 1991 =South America In South America, which had remained largely unglaciated except for increased mountain glaciation in the Andes , there was a contemporaneous but smaller wave of extinctions. =Australia (circa 26000-15000 BP) the sudden spate of extinctions came earlier than in the Americas, but lagged well after the first arrival of humans. The Australian extinctions included:
Some extinct megafauna, such as the Bunyip -like diprotodon, may be the sources of ancient Cryptozoological Legends . Younger prehistoric extinctions New Zealand c. 1500 AD, several species became extinct after Polynesia n settlers arrived, including:
Pacific, including Hawaii Recent research, based on Archaeological and Paleontological digs on 70 different islands, has shown the numerous species went extinct as people moved across the Pacific, starting 30,000 years ago in the Bismarck Archipelago and Solomon Islands (Steadman & Martin 2003 ). It is currently estimated that among the bird species of the Pacific some 2000 species have gone extinct since the arrivial of humans (Steadman 1995 ). Among the extinctions were:
Madagascar Starting with the arrival of humans c. 2000 years ago, nearly all of the island's megafauna became extinct, including:
Indian Ocean Islands Starting c. 500 years ago, a number of species became extinct upon human settlement of the islands, including:
THE ONGOING HOLOCENE EXTINCTION Megafaunal extinctions have continued to the present day. Modern extinctions are more directly attributable to human influences. Extinction rates are minimized in the popular imagination by the survival of captive trophy populations of animals that are merely "extinct in the wild," (Père David's Deer, etc) and by marginal survivals of highly-publicized megafauna that is "ecologically extinct" ( Giant Panda , Sumatran Rhinoceros , the North American Black-Footed Ferret , etc.) and by unregarded extinctions among Arthropod s. Some notable examples of modern extinctions of "charismatic" mammal fauna:
Many birds have become extinct as a result of human activity, especially birds Endemic to islands, including many flightless birds (''see a more complete list under '' Extinct Birds ). Notable extinct birds include:
Most biologists believe that we are at this moment at the beginning of a tremendously accelerated anthropogenic mass extinction. E.O. Wilson of Harvard, in ''The Future of Life'' (2002), estimates that at current rates of human destruction of the biosphere, one-half of all species of life will be extinct in 100 years. In 1998 the American Museum of Natural History conducted a poll of biologists that revealed that the vast majority of biologists believe that we are in the midst of an anthropogenic mass extinction. Numerous scientific studies since then—led by the 10,000 scientists who contribute to the IUCN 's annual Red List of threatened species—have only strengthened this consensus. Our evidence for all previous extinction events is geological evidence, and the shortest scales of geological time usually are in the order of several hundred thousand to several million years. Even those extinction events that were caused by instantaneous events — the Chicxulub Asteroid impact being currently the demonstrable example — unfold through the equivalent of many human lifetimes, due to the complex ecological interactions that are unleashed by the event. There still is debate as to the extent to which the disappearance of megafauna at the end of the last Ice Age can also be attributed to human activities, directly, by hunting, or indirectly, by decimation of prey populations. While Climate Change is still cited as another important factor, anthropogenic explanations have become predominant. Those who are skeptical about the impending mass extinction argue that even if the current rate of extinction is higher than the rate during a great Mass Extinction Event , as long as the current rate does not last more than a few thousand years, the overall effect will be small. There is still hope, argue some, that humanity can eventually slow the rate of extinction through proper ecological management. Current socio-political trends, others argue, indicate that this idea is overly optimistic. Most hopes are set on Sustainable Development and moderate forms of Primitivism . EXTERNAL LINKS
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