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Oct. 14, 2007 North American wildlife pales in comparison to the impressive variety of large mammals living in Africa today, but only 13,000 years ago the new world was more spectacular. Africa has one elephant species; North America had two kinds of mammoth (the Columbian and the wooly) and the mastodon. The American mammoths were closely related to Indian elephants but they had longer hair, a more domed forehead, and the trunks had a more flexible tip. Mastodons, which were common in the eastern half of the continent, looked like mammoths but were shorter, bulkier, and had a sloping forehead. We would recognize these beasts, but the giant ground sloths would astound most people unfamiliar with paleontology. Their closest living relatives are the tree sloths living in the tropical jungles of South America. They weigh about ten pounds. Eremotherium, one of about a dozen species of ground sloths, left fossils occasionally found in Georgia and Florida. It stood twenty feet tall and weighed three tons. The animal had huge claws and walked on its knuckles but despite its fearsome appearance, only ate plants. Big stratified sloth dung piles are found in several caves, giving solid evidence of their vegetarian diet. The glyptodont--a square-jawed giant, the size and shape of a Volkswagon--is difficult to imagine. Related to armadilloes, it had a shell almost like a turtle. Picture a mammal with a shell. It too ate plants, but its relative, the pampathere, was a giant armadillo the size of a bear that ate insects. Everyone's heard of Smilodon fatalis, the saber-toothed cat. They had powerfully built forequarters, like a Siberian tiger on steroids, and they used those big muscles to wrestle down juvenile mammoths, their fangs finishing the job with a bite to the neck. The American lion, a subspecies of the African lion and not to be confused with the extant cougar, lived in the open spaces of North America, and jaguars, the size of tigers, lived in the forested areas as far north as Pennsylvania. Along with several kinds of wolves and the long-legged and massive short faced bear, they preyed on the abundant buffalo, horses, camels, deer, peccaries, tapirs, giant beavers, and another giant rodent, the capybara. The resulting carrion was scavenged by the terratorn, a bird with a twelve foot wingspan; condors, and six kinds of eagles. What happened to all this wildlife? The answer is predictable: man, specifically the Clovis culture-a group of paleo-Indians who used throwing spears with rather large arrowheads that are commonly found in archaeological sites. Although many archaeologists and paleontologists still believe climate change caused the extinction of the megafauna, Paul Martin's overkill hypothesis makes far more sense and all recent studies tend to support his view. (Read his book: Twilight of the Mammoths) The previous history of the Pleistocene simply debunks climate change as a cause of extinction for near time megafauna. During the past two million years, there have been four major ice ages along with four corresponding warming periods or interglacials. Moreover, there have been dozens of minor yet dramatic surges between warm and cold periods. The scientists who think climate change caused the extinctions say the plant communities the large herbivores depended on became disturbed. However, almost no plant species became extinct. The species of plants found in the dung left by mammoths and sloths in caves still exist abundantly. In the previous shifts of climate there were no major across-the-board extinctions of genera during the Pleistocene. Only when man appears in the fossil record, do the animals disappear. If climate change caused extinctions of large mammals, it would have extirpated the small mammals too, but there were few recent extinctions among smaller species. Perhaps the best examples of anthropogenic-caused extinctions occured on islands. Humans appeared in Australia 45,000 years ago, exactly when large marsupials and the island's top predator, the thirty foot long lizard, megalania, vanished. Mammoths became extinct in North America about 12,500 years ago, yet survived on Pribiloff Island until 4,000 years ago when humans must have discovered the place. Ground sloths became extinct in North America the same time as the mammoths, but lived on in Cuba until humans discovered it, 6,000 years ago. The giant moa birds lived in New Zealand until humans settled there a thousand years ago. Mathmatical models of human population growth support Martin's overkill hypothesis, and isotope studies of Mastodon tusks, dating from close to the time of extinction, show they were well fed, not starving from lack of food caused by climate change. There are also numerous direct kill sites of mastodon and mammoths (with arrows embedded in bone), though this is still not enough evidence to satisfy the naysayers. Paul Martin proposes allowing wild horses to live in our national parks and favors the introduction of other exotic animals to restore the natural balance. Wouldn't that be nice? Ranchers and developre would probably disagree. ------------ About the author Mark Gelbart: My book, Talk Radio, is a black comedy about a radio talk show host who gets kidnapped and psychologically tortured by a loser. http://www.authorsden.com/marksgelbart Email: agelbart@aol.com Comment on this article here! ------------ All articles are EXCLUSIVE to Useless-Knowledge.com and are not allowed to be posted on other websites. ARTICLE THIEVES WILL BE PROSECUTED! |
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