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Anatomical, vestigial structures in vertebrates; specifically focusing on humans Buckland-Nicks, J. A., M. Gillis, and T.E. Reimchen. "Neural Network Detected in a Presumed Vestigial Trait: Ultrastructure of the Salmonid Adipose Fin." Proceedings of the Royal Society (2011): n. pag. Print

Although not focusing in on human vestigial traits, this journal piece describes the salmonid adipose fin of the brown trout. This fish is a vertebrate, and it goes into discussion of how to test to see if a trait or structure is indeed under the classification of vestigial. Cotner, Sehoya, and Randy Moore. Arguing for Evolution: An Encyclopedia for Understanding Science. Santa Barbara, CA: Greenwood, 2011. Print. A work that has a sole focus of arguing the legitimacy of evolution. Using comparative anatomy, homologous structures, and focusing in on vestigial traits, it seeks to accomplish such. It goes into detail describing various vestigial structures of a number of organisms. For this purpose, it goes into discussion of the human/primate tailbone.

"Darwin Was Right | Vestigial Structures." Darwin Was Right | Vestigial Structures. N.p., n.d. Web. 14 Sept. 2014.

An article that discusses in depth various vestigial structures of humans. It goes on to explain the theory of Charles Darwin and how these traits are related to the past. The article speaks on plica semilunaris and a number of other anatomical vestigial structures that humans still possess currently.

Schwartz, Peter H. Proper Function and Recent Selection. Vol. 66. Chicago: U of Chicago, 1999. Print.

Goes into detail discussing natural selection and evolution. In terms of vestigial traits, it discusses how traits originated to have a proper function. With this, as time goes on, the proper function of vestigial traits was lost. Especially that of the coccyx, wisdom teeth, and more in the human form.

Walker-Larson, Jennifer, and Lawrence D. Harder. "VESTIGIAL ORGANS AS OPPORTUNITIES FOR FUNCTIONAL INNOVATION: THE EXAMPLE OF THE PENSTEMON STAMINODE." BioOne Online Journals. N.p., 2000. Web. 14 Sept. 2014.

This article discusses the formation of vestigial organs and how they commonly arise during morphological evolution. With this, they are not destined for removal due to the fact that at one point, they likely served a distinct purpose.

FINAL DRAFT STARTS HERE

Tina Bennett Vestigial Traits: As Displayed in Humans Tuesday, 10:20 am Matt Holding Having a firm grasp on the idea of evolution is vital knowledge. If one does not have a solid handle on the subject, progressing further with science is useless. A topic that arises often times when studying evolution is the presence of vestigial traits. Vestigiality, biologically speaking, refers to organisms retaining organs, which have seemingly lost the entirety of the original function. The issue is controversial and not without dispute; nonetheless, vestigial organs are common, evolutionary knowledge (Christensen, Delahousse, Meganic, 2009). Historically speaking, vestigial structures have been known and studied for an extended amount of time. In fact, Aristotle briefly touched on this notion in his History of Animals. Although he did not know the fine, minute details of vestigiality, he referenced them when writing on the eyes of moles. He described them as “stunted in development” due to the fact that moles can scarcely see (Aristotle, 350). Later in time, though no term had been coined for vestigial traits, Charles Darwin was acutely aware of their existence. He realized that though a trait may be utterly useless for its original function, anatomical significance may still remain. In the year 1893, the term “vestigial” was coined by German anatomist, Robert Wiedersheim. In his The Structure of Man: An Index to his Part History, Wiedersheim listed eighty six human organs and features that he deemed vestigial (Wiedersheim, 1895). A common vestigial organ present in modern humans is the appendix. The appendix is a vermiform appendage located in the lower right portion of the abdominal cavity. Through the course of medical history, the purpose for the appendix has been searched for. Current research suggests the appendix may have a function above being a rudimentary remainder. It has been proposed that the appendix serves as a safe house of sorts for symbiotic bacteria (Choi, 2009). Regardless of this new found information, the notion that the appendix is indeed a shrunken remainder of the large intestine is still widely accepted (Knowles, De Giorgio, 2008). Another trait that arises in terms with vestigiality is the coccyx. The coccys is a part of the pelvic girdle, which makes up part of the human axial skeleton. The coccyx, more practically known as the tailbone, is the rudimentary, undeveloped tail humans possess. With this, all mammals have tails at one point in their development. The tail is present during embryological development. Furthermore, it exists for a period of only four weeks (Saraga-Babic, Lehtonen, Svajger, Wartiovaara, 1994). The original function of the coccyx was assisting in balance and motility. Though, through evolution and not being beneficial to the human body as a whole, the function has been lost. Though vestigial, the coccyx serves as an attachment point for muscles including: the levator ani muscle and the largest gluteal muscle, the gluteus maximus (Foye, 2014). As previously stated, though normally present only during embryological development, there is always an exception. There have been thirty-three cases of true human tails reported in current times (Spiegelmann, 1985). Clearly, this tail formation is a rarity. Though exceptional, these cases shine light on the notion that humans, at one point, likely had tails. And, over the course of time, they were selected against. With this, humans of today are without these tails. In addition, with these cases, the skull and spine were determined to be entirely normal. The sole abnormality resided with the tails. They were reportedly approximately twelve centimeters long. Furthermore, they were removed surgically with no further complications to the patient (Spiegelmann, 1985). Another example of an anatomical, vestigial trait is that of the wisdom teeth. These teeth are molars that are considered useless, currently. At times, these teeth become trapped in the jawbone of an individual. Even further, some individuals never even develop the wisdom teeth. It is believed that these third molars were used at one point to aid in grinding down plant tissue. With larger jaws and more teeth, The common ancestor to humans used these molars to break down cellulose present in the cell wall of the plant. As time went on, humans, along with their diets, changed and evolved. With this change, smaller jaws were selected. Yet, these third molars, or wisdom teeth, remained. Hence, how they can get trapped in the jaws of individuals (Johnson, 2002). With the trouble and pain they cause, wisdom teeth are often times removed. A less commonly known vestigial trait is in regards to the human ear. Clearly, the ear itself is not vestigial in nature. Instead, various muscles surrounding the ear fall under this classification. These muscles are large, yet essentially nonfunctioning. They cannot move the ear, and for this reason are not considered operative (Blaire, 1901). Like the previous structures, at one point, these muscles likely served a function. Such can be seen in another, nonhuman primate. Specifically, the Macaque monkey has muscles around the ear that are increasingly more developed than that of humans. This amplified development allows the monkeys to move their ears in order to hear inauspicious noises (Macalister, 1872). Anatomical vestigial traits are not the only type prevalent in humans. Some behavioral traits remaining that fall under the terminology vestigial are established, as well. The most well known is that of goose bumps. The arrector pili muscle, which is a band of smooth muscle that connects the hair follicle to connective tissue, contracts and creates the goose bumps on skin. Evolutionarily, when the common ancestor of humans was still covered with hair, goose bumps would have raised the hair. This action would make the individual seem larger in order to ward off predators. Think in terms of a cat; when a cat feels like it’s threatened, it raises the hair on its back. In addition, hair rising could have been used in order to trap and extra layer of air close to the skin of the creature. Such would aid in keeping warm (Torkamani, Rufaut, Jones, Sinclair, 2014). Another behavioral trait is the palmar grasp reflex. When one touches the palm of an infant, he or she will clutch it. This reflex can be attributed, again, to past body hair covering. By this, the infant would cling to its mother’s body hair in order to stay attached. Now, humans are not covered in enough body hair to support such a thing. However, the palmar grasp reflex has remained (Coyne, 2010). Through examination of these various traits, it is clear that evolution had a hard role in the development of humans. Every anatomical structure or behavior response has origins in which they were, at one time, useful. As time progressed, the ancient common ancestor of humans did as well. Evolving with time, natural selection played a huge role. More advantageous structrues were selected. While others, like large jaws, were not. With this expansion, some traits were left to the wayside. Today, these are known as vestigial. Furthermore, these qualities give insight to humans and ancestors of the past. Vestigial traits are “sufficient to make a man a veritable walking museum of antiquities” (Darrow, Bryan, 1997).

Works Cited

Aristotle. 350. Full Text of Aristotle’s History of Animals in ten books. Internet Archive. 19 October 2014. Blaire, J.H. 1901. Development of Voluntary Control. PsycNET. Vol 8(5). 20 October 2014. Choi, Charles Q. 2009. The Appendix: Useful and in Fact Promising. LiveScience. TechMedia Network. 20 October 2014. Darrow, Clarence and William J. Bryan. 1997. The World’s Most Famous Court tRial: The Tennessee Evolution Case Pub. The Lawbook Exchange, Ltd. 19 October 2014. Christiansen, Steen H., Bernard Delahousse, and Martin Meganck. 2009. Engineering in Context. Google Books. 20 October 2014. Foye, Patrick M. 2014. Medscape. 20 October 2014. Coyne, Jerry. 2009. Why Evolution is True. Penguin Group. 20 October 2014. Johnson, George B. 2002. Evidence for Evolution. 20 October 2014. Knowles, C.H., and R. De Giorgio. 2008. Observations on a Vestigial Organ: A Potential Surrogate for Enteric Neuromesenchymal Disease. Wiley Online Library. 20 October 2014. Saraga-Babic, M., E. Lehtonen, A. Svaiger, and J. Wartiovaara. 1994. Morphological and Immunohistochemical Characteristics of Axial Structures in the Transitory Human Tail. National Center for Biotechnology Information. U.S. National Library for Medicine. 20 October 2014. Macalister, A. 1872. Annals and Magazine of Natural History. Vol. VII. 19 October 2014. Spiegelmann, Roberto, E. Schinder, M. Mintz, A. Blakstein. 1985. The Human Tail: A Benign Stigma. JNS. 19 October 2014. Torkamani, Niloufar, Nicholas W. Rufaut, Leslie Jones, and Rodney D. Sinclair. 2006. Beyond Goosebumps: Does the ARrector Pili Muscle Have a Role in Hair Loss. National Center for Biotechnology Information. U.S. National Library of Medicine. 20 October 2014. Wiedersheim, Robert. 1895. The Structure of Man: an Index to His Past History. 20 October 2014.

My edits to wikipedia pages include: Vestigiality: in the overview section, history section, common descent and evolutionary theory section, and Humans section.