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Evolutionary development of modern giraffe body parts
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The Evolution of the Giraffe Neck
Throughout time, one theory has remained constant in terms of why giraffes developed longer necks. The idea, which was presented by Charles Darwin states quite simply that giraffes selected for longer necks in order to reach the food that was higher off the ground during the dry season. No one has ever challenged that idea until 1996. Initially, Gould argued that "the story-the giraffe evolved its long neck in competition to reach scare foliage-is supported by no evidence" (18). That's when two scientists, Robert Simmons and Lou Scheepers made the claim that necks evolved for a very different reason: sexual selection. Within this paper, information will be presented that argues both for and against the theories made by Darwin and Simmons and Scheepers.
Giraffes are placed in the family, Giraffidae, separate from other animals such as the camel, deer, and cow. Typically, giraffes are about 19 feet tall and can weigh as much as 4000 pounds. The evolution of modern giraffes began about 1 million years ago from a similar species known as Giraffa jumae. Those species were known for their massive skeletons and antler-like structures, not found on giraffes of today (Simmons 772). Today, there are nine widely excepted subspecies of the giraffes which are differentiated by the spots on the trunks and their geographic region.
In the article, "Winning By a Neck: Sexual Selection in the Evolution of Giraffes," Simmons and Scheepers state their purpose as to evaluate the theory proposed by Darwin as well as present their own. The theory by Darwin known as the Interspecific Feeding Competition has many assumptions that must hold up for it to be true. One assumption is that tall trees must ...
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... This is shown through the way that the animals feed and the disproportionate increase in neck length compared to other components within the giraffe. The evidence presented in this case offers much more support for the idea that sexual selection is responsible. However, much more investigation must take place in order for the theory to be considered acceptable.
Bibliography:
Works Cited
Brownlee, A. Evolution of the Giraffe. Nature. Vol. 200:1963.
Pp. 1022.
Gould, Stephen J. The Tallest Tale. Natural History. May 1996.
Pp. 18-27.
Kodrick-Brown, A., and J. H. Brown. Truth in Advertising: The
Kinds of Traits Favored by Sexual Selection. The American
Naturalist. Vol. 124:1984. Pp. 309-323.
Simmons, Robert E. Winning By a Neck: Sexual Selection in the
Evolution of Giraffe. The American Naturalist. Vol.
148:1996. Pp. 771-786.
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Darwin: A Norton Critical Edition, Second Edition ; ed. by Philip Appleman; copyright 1979, 1970 by W.W. Norton & Company, Inc.
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In relation to the findings, two specific species of primates have been found to have coexisted separately in particular locations explored in Kenya. The way they are separated from each other specifically notes how these groups of primates were able to protect themselves from cross breeding with each other. The first specie, Praeanthropus dimorphicus, is notably a predator which could be assumed to have fed on animals surrounding the area. Based on the fossils found on top of the fossils of this specie, these primates could be assumed to have fed on wildebeests ...
Did you know thousands of years ago giraffes did not only live in Africa, but they also lived in North America? We do not see these species in North America anymore because they all died because of their inability to adapt. Giraffes adapted into their environment because the food they were eating was on taller trees and after a while, only the selection with longer necks were left. The giraffes we see today, have longer necks because they are the ones that survived by adapting. As all other animals, giraffes are living things because they get energy, move and grow, reproduce, protect themselves, and adapt to their environment.
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With the studies that Charles Darwin obtained he published his first work, “The Origin of Species.” In this book he explained how for millions of years animals, and plants have evolved to better help their existence. Darwin reasoned that these living things had gradually changed over time to help themselves. The changes that he found seemed to have been during the process of reproduction. The traits which would help them survive became a dominant trait, while the weaker traits became recessive. A good example of what Darwin was trying to explain is shown in giraffes. Long-necked giraffes could reach the food on the trees, while the short-necked giraffes couldn’t. Since long necks helped the giraffes eat, short-necked giraffes died off from hunger. Because of this long-necks became a dominant trait in giraffes. This is what Charles Darwin would later call natural selection.
Long neck, camel-like shape, panther like shading and horn-like ossicones don't make everyone wonder what happened: giraffes are actually odd. What might happen if changes began transpiring? Consolidate giraffes to develop them and find their most inquisitive, outlandish and odd structures!
The increase in brain size may be related to changes in hominine behavior (See figure 3). The third major trend in hominine development is the gradual decrease in the size of the face and teeth. According to the Microsoft Encarta Encyclopedia ’98, the fossil evidence for direct ancestors of modern humans is divided into the category Australopithecus and Homo, and begins about 5 million years ago (See figure 1). Between 7 and 20 million years ago, primitive apelike animals were widely distributed on the African and, later, on the Eurasian continents (See figure 2). Although many fossil bones and teeth have been found, the way of life of these creatures, and their evolutionary relationships to the living apes and humans, remain matters of active discussion among scientists.
If the very first giraffe had a long neck and about a 2 foot long heart, but no mechanism to regulate it, when he first bent down to get a drink he would have exploded his brain. Then after his brain would have exploded, he would thought “I need to evolve valves in my arteries to regulate this.” No he would have blown up and died. The giraffe’s extremely long neck couldn’t have been evolved, it had to be completely working in the first place(inplainsite.org).