Wait a second!
More handpicked essays just for you.
More handpicked essays just for you.
Impact of fighting on giraffe neck evolution
Migration theory of giraffe's origins
Don’t take our word for it - see why 10 million students trust us with their essay needs.
Recommended: Impact of fighting on giraffe neck evolution
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...
... middle of paper ...
... (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.
"Giraffe." National Geographic. Web. 26 Feb. 2012. .
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.
1) Carroll, R. L. 1988. Vertebrate Paleontology and Evolution. W. H. Freeman and Company, New York.
Not only are giraffes the tallest animals in the world, they are also one of the most recognizable. Their characteristic long necks quickly captivate any audience. That being said, it is not commonly known that there are thought to be nine subspecies of Giraffa camelopardalis. In fact, there is increasing evidence that these could potentially be separate species in their own right. This paper will discuss where giraffes fit in the Tree of Life and identify the giraffe’s closest relatives, differentiate and analyze the similarities and differences between the nine subspecies, and, finally, explore any debate revolving around the phylogeny of the subspecies.
Web. The Web. The Web. 11 February 2014 “Biology: Evolution”. The New York Public Library Science Desk Reference.
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
Manson, J.H.; Perry, S.; Parish, A.R. (1997). "Nonconceptive Sexual Behavior in Bonobos and Capuchins". International Journal of Primatology 767–86
Dr. Goodall is a well-known British primatologist who has discovered a substantial amount about primates in her many years of research. She has written numerous books, including one that we will be going into depth about called, “Through a Window.” Her book contains personal experiences, research findings, and even pictures to help the readers visualize her scientific breaking moments from her thirty years with the chimpanzees of Gombe. She states that there is are minor differences, and several similarities between humans and the chimpanzees. We will discuss these differences and similarities through their social behavior, intellectual ability, and emotions. To conclude, examine Goodall’s research to adopt what her findings can tell us about our early ancestors, and whether or not her study coincided to the steps of scientific methodology.
The evolution of man is constantly in question. While we are reasonably sure that modern humans and primates are both related to the same common ancestor, there is constant debate over what initially caused the two species to split into early hominids and apes. According to some, our longest and most popular theory on the division of man and ape is profoundly wrong. However, those same individuals usually offer an equally controversial theory as a substitute, one that is almost impossible to scientifically test or prove. Both the Savanna Theory and the Aquatic Ape Theory offer solutions to how and why humans evolved into bipedal toolmakers. But with enough questioning, each loses its accountability to rhetorical science.
Quiatt, D., & Reynolds, V. (1993). Primate behaviour: information, social knowledge, and the evolution of culture. Cambridge [England: Cambridge University Press].
Display, communication, and the act of mating are estimated behaviors involved in the mating process of dinosaurs. The sexual behaviors of modern vertebrae are often used as a starting point to estimate that of dinosaurs. For instance, most modern vertebrae go through a sexual selection process as they choose their mate based on preferred traits. This is demonstrated with the modern day peacock. The visual stimulus the male provides with its tail feathers aids in the opposite gender’s sexual selection process. According to Martin, in this respect, the ceratopsians have the most obvious sexual displays in the form of ornate and broad head shields with horns, knobs, and bosses. Though these body parts could definitely prove useful to fend off potential predators, it is more likely that they were used for: visual recognition within their species; pote...
Due to their close evolutionary relationship to humans, chimpanzees and bonobos have been widely studied and used as models for the behavior of early hominids. In recent years, new information regarding the social behaviors and ecology of bonobos has come to light, and this has warranted many interspecific comparisons between bonobos and chimpanzees: “Chimpanzees have been characterized in terms of their intercommunity warfare, meat eating, infanticide, cannibalism, male status-striving, and dominance over females. Bonobos, meanwhile, have been portrayed as the ‘Make love, not war’ ape, characterized by female power-sharing, a lack of aggression between either individuals or groups, richly elaborated sexual behavior that occurs without the constraint of a narrow window of fertility, and the use of sex for communicative purposes” (Stanford 399). Over the course of this paper, I will provide evidence for the dichotomy between these two species, with particular attention to the histories of their research, the nature of their social interactions, as well as their sexual behaviors.
World Archaeology, 31:3:329-350. Mitani, J.C. et al 1996 Sexual Dimorphism, the Operational Sex Ratio, and the Intensity of Male Competition in Polygamous Primates. The American Naturalist, 147:6:966-980. Rogers, Alan R. and Arindam Mukherjee 1992 Quantitative Genetics of Sexual Dimorphism in Human Body Size.
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.
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...
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.