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7710 - Climate Change -- A valid alternative for Pleistocene megafauna extinctions.

Five major mass extinctions in history, the last one being the K/T boundary, have occurred. Among the minor mass extinction events, the most outstanding is the late Pleistocene extinctions where most of the megafaunal species became extinct, many of which were known to people. A standing controversy is present in the Americas in terms of the cause of the extinctions. One group supports a biological-geological explanation, and mostly drastic climate change. Others prefer an anthropological cause as the main extinction driving force, either direct (decimating animal populations) or indirect (damaging pristine habitats). Among the overall faunal components, the megafauna, those animals weighing above 100 kg, were the weight class that suffered major loss, with 72% from the total number in North America (28 extinct genera), and even a larger effect in South America with 48 extinct genera (83%). The direct cause for many species may be vegetation changes that were taking place that resulted in habitat loss or fragmentation. The existence of these huge animals depended upon an environment rich in nutritious plants, such as temperate grasses or tropical trees that disappeared or retracted to the north at the end of the Pleistocene. Mammoth and bison are examples of different responses to these changes. Mammoth appears to be an example of biomic specialization, a stenebiomic species restricted to a unique biome and one to a few vegetation types. They could not adapt to the changes and appear specialized to a particular type of grassland. Although bison is an obligate grazer, both its genome and grass type on which it fed are flexible enough to allow adaptation to the early Holocene short-grass prairie. The effect is a domino one in that extinction of the large herbivores resulted in loss of prey for the Pleistocene megacarnivores that lead to their extinction.

Co-Author: Eileen Johnson, Museum of Texas Tech University, Lubbock, Texas, USA.

Keywords: megafauna, extinction, habitat loss, vegetation change, climate change

Author: JOAQUIN, ARROYO-CABRALES (INSTITUTO NACIONAL DE ANTROPOLOGIA E HISTORIA, Mexico / Mexiko)
Co-Author: Johnson, Eileen (Museum of Texas Tech University, Lubbock, USA)

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