Introduction
At a height of 18 feet, the giraffe is extremely unique and the world’s tallest mammal. All nine species of giraffes are found in Africa, which limits the amount of research that has been done with them (“Giraffe”). Some analysis on this mammal has been performed, and one immense question surrounding the giraffe is the origin of the evolution of its long neck. From many of the studies done over the years, two hypotheses have arisen. Some scientists believe the cause of the evolution of the giraffe’s increasing neck length is due to sexual selection, while others argue it is due to competing browsers. The sexual selection hypothesis argues that the larger males with longer necks are dominant against smaller males in fights for mating access with female giraffes. The competing browsers hypothesis argues that giraffes feed at a higher level to avoid competition with other organisms for food. Scientists agree evolutionary changes have occurred in giraffe’s necks, but the origin of this evolution is unclear. In this paper, I will describe the two hypotheses in detail and give supporting evidence for each. I will also show contradicting evidence and refute each argument. The evolution of the neck length in giraffes has been disputed among scientists for many years, and will continue to be in future years.
Evolution by Sexual Selection
When two male giraffes fight using their heads and necks as clubs to bash each other it is commonly referred to as “necking” (Simmons and Scheepers 1996). These fights occur because there is competition for priority in mating with estrous females. Female giraffes prefer the stronger, dominant males to mate with so they will have successful offspring. Through fossil evidence from the last...
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... (Giraffa camelopardalis) cervical vertebral column: a heuristic example in understanding evolutionary processes? Zoological Journal of the Linnean Society 155:736-757.
Cameron E. Z. E., du Toit, Johan T JT. 2007. Winning by a neck: tall giraffes avoid competing with shorter browsers. The American naturalist 169:130-135.
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Mitchell G., S. J. van Sittert, and J. D. Skinner. 2009. Sexual selection is not the origin of long necks in giraffes. Journal of Zoology 278:281-286.
Simmons R. E., R. Altwegg. 2010. Necks-for-sex or competing browsers? A critique of ideas on the evolution of giraffe. Journal of Zoology 282:6-12.
Simmons R. E., L. Scheepers. 1996. Winning by a neck: Sexual selection in the evolution of giraffe. American Naturalist 148:771-786.
de A, Moura A, Lee P. "Wild Capuchins Show Male-biased Feeding Tool Use." International Journal of Primatolgy 31.3 (2010): 457-470. Academic Search Premier. 25 April 2014. .
...s much of the time that some people have been led to believe. This belief had begun when they had discovered a fossil that has since been given the title “Selam”. “Selam” is the skull of a three year old female Australopithecus Afarensis who is believed to have been alive about 3.3 million years ago, having been discovered in the year 2000 in Ethiopia, Dikika by a paleoanthropologist named Dr. Zeresenay Alemseged. With Selam they have found that with the skeleton of her, that it shares many similarities when compared to the bone structure of an ape, meaning that the A. Afarensis may have lived a somewhat arboreal lifestyle. They at first checked the shoulder blades of “Selam”, with both remaining in fully intact which is considered to be very rare due the fact that the shoulder blades had remained intact through 3.3 million years, as it would allow them to find out
As our neighboring living families, chimpanzees as well as bonobos have been extensively used as prototypes of the behavior of early hominids. However, In modern years, as statistics on the social behaviors or conduct and ecosystem of bonobos has evidently come to light, a lot of interspecific assessments have been done. Chimpanzees have been described in terms of their intercommunity struggle, meat eating, infanticide, anthropogy, male position-striving, and supremacy over females. Bonobos, for the meantime, have been depicted as the ‘‘creator of love, but not a war’’ ape, categorized by female power-sharing, a deficiency of hostility between either characters or groups, expounded sexual behavior that happens without the restraint of a thin window of fruitfulness, and the usage of sex for communicative determinations. This paper evaluates the indication for this contrast and reflects the reasons that distinct portrayals of the two great apes have advanced.
Approximately 4 million years ago a wonderful evolutionary phenomenon was happening in Africa. Early hominids, man’s ancestors, were beginning a giant leap in their evolution. These hominids were moving out of the forest and beginning to walk upright, out on the open plains (Fagan, 98). This change from quadrupedalism was the most significant adaptation that ever happened to these early hominids. It caused many adaptations that make man what he is today. This process occurred in early hominids for many different reasons, each reason helping to perfect the upright walking posture. Bipedalism is thought to have occurred because of changes in environment, feeding habits, thermal regulation, and behavioral mechanisms.
Kappeler et al (2003) suggest that life history variables also should be included within the socioecological model due to the inferences and conclusions that can be devised of the behavioural ecology of primates. The framework is under constant remodeling due to the new challenges that arise as the variation being observed does not fit within the model’s predictions (Janson, C., 2000). This is likely due to the role of the environment and its significant impact on studies due to the restriction on study sites and opportunities and the unlikelihood of having been able to study primates with no human influence if possible are under high security. And even the impact of the physical environment has been shown to impact the social organization of primate groups (Fiore, A. D., et al, 1994). There is also further research that suggests the significance of the role of infanticide as a reproductive strategy in many primate species (Van Schaik, C. P. et al., 2000). This action is used by the males of the species to eliminate the offspring that pose risk to the male’s reproductive success by extending the time of female
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 ...
Gould, Edwin, George McKay, and David Kirshner. Encyclopedia of Mammals. San Francisco, CA: Fog City, 2003. Print.
First of all, in The Giraffe, people want to harm the tall animal because it creates an uncomfortable atmosphere, which can be seen through the reactions of many characters. As a result, everyone, except the boys, misunderstands the habits of the giraffe, and wants to kill it at the end. One clear example of a negative reaction to the presence of the giraffe can be shown through the police officer’s reaction to the presence of the giraffe: “[…] the policeman who came and said, ‘if you don’t take it away, I’ll kill it with my revolver’ (Senesi 3).” The officer of the law looks upon the giraffe from Africa as if it is a criminal. Since the ...
Lerner, E. and Lerner, B., 2008. Giraffes and okapi. The Gale Encyclopedia of Science 4
The giraffe conveys a strong message about how humans have an inability both emotionally and intellectually to deal with any kind of change. In this story a giraffe was brought in to the town by a merchant, lots of the people in the town were scared and frightened by the giraffe entering in the town. The people living there did not want to keep “the beast” in their town, showing their intolerance towards anything that changes or that is new. The intolerance was to such extremes that he people were ready to kill the animal, “We 'll have to kill the giraffe” (Senesi 30). The refusal to accept change in this story is a direct reflection of our society today. People are still scared to accept
Homo erectus is also known for its larger body compared to earlier ancestors. "Past estimates of Homo erectus stature frequently were in the 5-5 1/2 feet (152-168 cm) range for adult males and arou...
Gear, Kathleen O’Neal and Gear, W. Michael. “A Brief Look at the Evolution of Bison” lindnerbison. August 2010. Kathleen O’Neal Gear and W. Michael Gear. Web. March 30, 2014.
Ruff, S. D. (1999). The Smithsonian Book of North American Mammals. In S. D. Ruff, The Smithsonian Book of North American Mammals. Washington, DC: Smithsonian Institution Press.
Sikes, Roberts. and William L. Gannon. "Guidelines of the American Society of Mammalogists for the Use of Wild Mammals in Research." Journal of Mammalogy 92.1 (Feb. 2011): 235-253. Academic Search Premier. EBSCO. Web. 5 Oct. 2011.
One important and what I feel is the greatest animal studied in zoology is the giraffe also known as Giraffa camelopardalis. The giraffe is the tallest animal averaging seventeen feet. Giraffes usually weigh about 2,500 lbs. Giraffes along with their extremely tall bodies have tongues usually fifteen inches long.