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... vironments than do smaller animals. Larger animals are safer from predators than small animals are, but it is also harder for them to sustain in trying conditions. Many of the larger animals such as mammoths and bison travel in herds, and that, along with their large size, protects them from predators. However, when the predator is Mother Nature, there is virtually no defense. For modern day elephants, drought is the biggest concern.
It can take twenty percent of a herd every year, but the elephants continue to exist (Ward, 1997). It would have been harder though, for the mammoths and mastodons to survive a drought. Because of their size and weight, the Ice Age Proboscidea had longer gestation periods, which meant lower birth rates. If too much of the population was lost due to a severe drought, the population would be at risk. Also in the same time period of 10,000-12,000 years ago, the peopling of North America occurred. Although some archeological clues have hinted at earlier human occupancy, no site has manifested definite proof so let us assume for now that they in fact did arrive in this time period.
We know this because there are many archeological sites scattered all over North America that contain human artifacts. The first site from which artifacts dating back to the end of the Pleistocene were uncovered, was discovered in 1932. The site was found in a small town called Clovis in New Mexico. The artifacts that were unearthed were projectile points between two and five inches long, and the bones of extinct mammals. The projectile are curate, bifacial, fluted points. They came to be known as Clovis points, which now mark the earliest known human occupancy of North America, and are characteristic of the sites occupied by these people. The people who fashioned this tool are known as the Clovis People.
The Clovis people migrated to North America, as the many animals did, via the Bering Land Bridge. Although the timing and extent of human contact with the megafauna is ambiguous, it is clear that the Clovis people did encounter and kill the now extinct mammals. The debate is whether or not humans were the sole cause of mass extinctions during the Late Pleistocene. Paul Martin of the University of Arizona hypothesized that with a rapidly growing and spreading population of big game hunters and wasteful hunting methods, the animals became extinct. He claimed hunters would consume only a small portion of the kill leaving much waste. This supposedly resulted in overkill of animal population and subsequent extinctions (Fagan, 1995:85).
Martin also brought up the point that if the changing climate was the cause, horses would not be able to survive in the present. The reason being that the climate, and environment at the end of the Ice Age was much like that of today, and if the horse could not sustain then because of climate alone, they would not be able to sustain, let alone flourish as they do presently in North America (Grayson, 1993). Twelve sites in North America that bear Clovis points in stratigraphical order with mammoth bones have been discovered. One of these is the Lehner site. It is located in the San Pedro Valley in Cochise County of southeastern Arizona. Ed Lehner discovered mammoth bones in 1952 on property that he later purchased (Grayson, 1993).
Emil Haury, an archeologist of the University of Arizona began excavating the site in 1955. In the San Pedro Valley, a layer of black organic clay called the black mat lies at the base of Holocene sediment. The clay contains remnants of a prehistoric marsh, and its lowermost layer dates back to 10,800 years ago. The artifacts were found deeply embedded in a stream bank under the black mat, and date to 10,900 years ago. In total, the bones of thirteen mammoths, one bison, and twenty-one stone tools have been unearthed at Lehner. Eight of the tools were probably used as expedient cutting devices, and the others were projectile points.
Eleven of the thirteen points were found in close proximity of the bones, indicating that they were used to kill the animals. The dry streambed near which the bones have been found, is named Mammoth Kill Creek. From the name and the findings at Lehner, it might seem like this site supports Paul Martins theory of overkill and wasteful hunting, but it is not even definite that all of the mammoths here were killed by man. The land around the stream used to be desert grasslands, and Mammoth Kill Creek was probably a watering spot for the animals. At this spot the some of the mammoths may have died natural deaths, and other were killed by humans. This was probably not a mass kill, because Clovis people generally would track herds and not take more than one animal of the herd. Both the case for climatic change and its role in extinction, and the case for overkill and its involvement, present some compelling evidence.
There is also room in either theory for debate. The most likely and seemingly obvious conclusion is that Mother Nature and humans worked together in the extinction process. Suppose the change in climatic conditions did affect the megafaunal population. Considering all of the changes that occurred, such as rising temperatures, receding glaciers, changing rainfall patterns, and rising sea levels from which large tracts of land became immersed, it is hard to imagine that the climate could not have had any affect, even if indirectly, on the Ice Age animal populations. Most plants are characteristic of the environments they live in. By looking at a particular type of plant, we can tell a lot about where it came from and in what kind of conditions it lived. Because plants are so specific to their environment, they do not adapt well to climatic changes. Therefore, the changes mentioned above must have affected the Late Pleistocene vegetational environments.
Mammoths and Mastodons were some of the largest mammals of the Ice Age, required large amounts of food. These, and many other animals were herbivores. When there was not enough vegetation, or enough of the right kind of vegetation to eat, the animals had to either migrate or adapt. If they were not able to migrate or adapt quickly enough, they would die. In order for any species to survive, the population must grow faster than its members are dying. This means, for the Ice Age mammals to resist extinction, the birth rate would have to have been higher than the mortality rate, so any other factors increasing the rate of mortality would seriously jeopardize the existence of the animals. Gary Haynes studied the two living species of present day Proboscidea (Loxodonta africana and Elephas maximus) to find out more about their prehistoric counterparts (Haynes, 1991). First, he compared them to each other, finding them ...different in physical appearance, but very similar in social behavior and biology, (Haynes, 1991:10).
He then related them to the Mammut and Mammuthus of the Ice Age. He found, through allometric scaling, that elephants and mastodons seem to have similar biological histories. The larger bone structures indicate that the mammut, although it doesnt differ much in actual size, would have weighed more than those of today. From this information, Haynes was able to deduce an assumption about reproductive patterns in the mastodon.. The longer gestation periods in the prehistoric animals, because of their heavier weight, implies slower reproduction. Haynes also discovered useful information about the ability of these animals to subsist in specific conditions. According to the studies, not only do they need a large amount of food, they also need water to aid in digesting the food, so both or either one of those missing factors would have impacted the mammoth and mastodon.
It is likely that towards the end of the Ice Age, megafaunal populations were seriously diminished, and perhaps for some genera, already extinct. The climate began to change 18,000 years ago, and humans didnt arrive until about 12,000 years ago. This meant that the changes were still occurring at the time of human arrival, and the animal populations would not yet have had a chance to recover. From the archeological sites containing projectile points together with bones of the megafauna, we know for sure that humans did kill the animals. People may have been the final component in the in extinction of the megafauna, but most likely not the only one. If climate change had not affected the faunal populations, the amount of animals on the continent when early people arrived would have been abundant.
It is improbable that man alone could have killed off thirty-five genera of animals in the period of two-thousand years. If climate change had been the only factor in depleting the megafaunal population, survival rates would likely have been high enough to sustain. Therefore, it is highly probable that the changing climate began the diminution of the megafaunal population, but that the process was extenuated by humans. Bibliography: BIBLIOGRAPHY Elias, Scott A. 1997 The Ice Age History of Southwest National Parks. Washington and London: Smithsonian Institution Press Fagan, Brian M.
1995 Ancient North America: The Archaeology of a Continent. London: Thames and Hudson Ltd. Fagan, Brian M. 1987 The Great Journey: The Peopling of Ancient America. London: Thames and Hudson Ltd. Fiedel, Stuart J. 1987 Prehistory of the Americas. Cambridge: Cambridge University Press.
Grayson, Donald K. 1993 The Deserts Past: A Natural Prehistory of the Great Basin. Washington and London: Smithsonian Institution Press Haynes, Gary. 1991 Mammoths, Mastodonts, & Elephants: Biology, Behavior, and the Fossil Record. Cambridge: Cambridge University Press. Sutcliffe, Antony J. 1985 On the Track of Ice Age Mammals. Cambridge: Harvard University Press Ward, Peter D. 1997 The Call of Distant Mammoths: Why the Ice Age Mammals Disappeared.
New York: Copernicus Van Couvering, John A. 1997 The Pleistocene Boundary and the Beginning of the Quaternary. Cambridge: Cambridge University Press..
Research essay sample on Ice Age Extinctions Of The Megafauna