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My draft was denied, so I submitted my new request onto the talk page for Giraffe. I accidentally forgot to tag the post with my username.

I submitted a draft for a new page entitled "The Neck of the Giraffe." The content is as follows:

The Neck of the Giraffe The neck of the giraffe (Giraffa camelopardalis) is often times seen as a great adaptation, when speaking in evolutionary terms. However, the evolutionary advantages of this long neck are often times disputed among evolutionary biologists. The long neck could be a product of sexual selection in giraffes; while on the other hand, it could be a product of the giraffe outcompeting other herbivores for higher food sources. This is a famous dichotomy that is continually being debated in evolutionary biology, as each side has some incredibly strong points as well as some inevitable shortcomings

The Competing Browsers Hypothesis This is the idea that giraffes evolved this extended neck to avoid competition with shorter herbivores. When Charles Darwin published his research entitled, On the Origin of Species, he explicitly mentions giraffes as having evolved by avoiding competition from shorter plant eating animals. In a study by Elissa Cameron and Johan du Toit, they decided to test this idea by using differential fence heights around certain trees in southern Africa, to show that giraffes gain a nutrient advantage over shorter browsers. Their experimental evidence revolves around a giraffe bite \unit, which is the idea that if more animals are feeding at a specific tree height, then the GBU will contain less leaf mass. On the other hand, if the portion of the tree is relatively untouched, the leaves will be overgrown and allow for a large GBU. The results concluded that giraffes actually receive more biomass per bite high up in the canopy, than their shorter competitors. This research supports their hypothesis that feeding efficiency in giraffes is reduced when they are forced to browse at lower heights. This places the giraffe in a highly advantageous system in which it is able to extend its neck to eat at highly dense leaf areas. At the same time, this proposes the idea that other animals living in similar environments as giraffes, such as impalas and kudu, are forced to eat at low tree levels, where leaf nutrition is scarcer. This seemingly perfect system allows giraffes to nutritionally thrive and thus, have a high fitness.

The Necks-for-Sex Hypothesis

The latter hypothesis, also known as the necks-for-sex hypothesis, was created by Robert Simmons and Lue Scheepers. Simmons and Scheepers denied the competitive browser hypothesis by stating a few “simple” ideas, while hypothesizing about intrasexual selection. They discovered that giraffes, in general, feed from low shrubs, and when doing so, feed faster than when feeding with their necks straight. Also, they found that females spend over 50% of their time feeding with their necks bent to eat at lower shrubbery. Therefore, feeding high in the canopy allows giraffes to gain a high nutritional advantage, then giraffes would not be eating at low shrubbery with their necks bent. Denying the conventional “competitive browsers” hypothesis, they hypothesized that males fight for females using their necks and armored heads in intrasexual conflicts. This intrasexual conflict is known as necking. Necking occurs when two male giraffes stand side by side and swing their necks at each other in a forceful manner (Scheepers, Simmons 1996). Their research shows that these necking battles arise when male giraffes come across an “estrous female.” These female giraffes give off pheromones that allow males to know when they are ready to mate. This necking is the only form of male fighting found in giraffes and is a way in which males can prove to females that their genes are of high fitness. Also, they hypothesized that males, on average, tend to have larger skulls and more massive necks than their female counterparts. From extensive research they discovered that this was indeed the case. They found that males in a dominant position in a population tended to have larger heads and necks than males in a non-dominant position. This supports the idea that males with heavier necks can outcompete smaller males, thus winning over estrous females.

FINAL DRAFT STARTS HERE
The Evolution of the Giraffe Neck The neck of the giraffe (Giraffa camelopardalis) is often times seen as a great adaptation, when speaking in evolutionary terms. An adaptation is a trait with a practical role in the life of an organism that allows that organism to be better suited to its environment, and consequently, produce offspring that are better suited to their environment. The long neck of the giraffe is always used as the “perfect” example of this idea. However, the evolutionary advantages of this long neck are often times disputed among evolutionary biologists. This idea of the long neck of the giraffe is incredibly important in evolutionary biology, as it was used by Lamarck to help bolster his theory of evolution. This theory basically stated that nature causes evolution by driving simple organisms to more complex organisms over time. However, even though many agreed with his central ideas, Lamarck’s use of the giraffe was met with much skepticism by his critics for a number of reasons. The long neck could be a product of sexual selection in giraffes; while on the other hand, it could be a product of the giraffe outcompeting other herbivores for higher food sources. This is a famous dichotomy that is continually being debated in evolutionary biology, as each side has some incredibly strong points as well as some inevitable shortcomings (Shuster 1982). In order to understand the enigma that is the giraffe neck, it is important to look at how exactly this neck evolved. In a 2009 study by Ludo Badlangana, Justin Adams, and Paul Manger, they studied vertebrae data spanning from adult giraffes to calves, as well as a number of other species closely related to giraffes. Through studying these organisms they found that the only set of vertebrate which selection acted upon in giraffes was the cervical vertebrae (of which there are seven, alike all other mammals), and that the rest of the vertebrae are normally sized (Badlangana et al. 2009). Also, they discovered that the giraffe vertebral column is that unlike any other in the animal kingdom; including okapi (Okapia johnstoni), a close relative of giraffes once thought to have been under the same evolutionary constraints. Lastly, they found that the cervical vertebrae take up over fifty percent of the vertebral column in giraffe, an incredibly simple, yet new finding (Badlangana et al. 2009). Surprisingly, not all that much is known about the evolution and morphology of vertebrae in giraffe. The first hypothesis regarding the evolution of the giraffe neck is the most conventional, and this is the idea that giraffes evolved this extended neck to avoid competition with shorter herbivores. When Darwin published his research entitled, On the Origin of Species, he explicitly mentions giraffes as having evolved by avoiding competition from shorter plant eating animals. In a study by Elissa Cameron and Johan du Toit, they decided to test this idea by using differential fence heights around certain trees in southern Africa, to show that giraffes gain a nutrient advantage over shorter browsers (Cameron, Toit 2007). Their experimental evidence revolves around a giraffe bite unit, which is the idea that if more animals are feeding at a specific tree height, then the GBU will contain less leaf mass. On the other hand, if the portion of the tree is relatively untouched, the leaves will be overgrown and allow for a large GBU. The results concluded that giraffes actually receive more biomass per bite high up in the canopy, than their shorter competitors (Cameron, Toit 2007). This research supports their hypothesis that feeding efficiency in giraffes is reduced when they are forced to browse at lower heights. This places the giraffe in a highly advantageous system in which it is able to extend its neck to eat at highly dense leaf areas. At the same time, this proposes the idea that other animals living in similar environments as giraffes, such as impalas and kudu, are forced to eat at low tree levels, where leaf nutrition is scarcer. This seemingly perfect system allows giraffes to nutritionally thrive and thus, have a high fitness. Cameron and du Toit provided the first evidence towards the hypothesis that giraffe’s bite size advantage gives them an advantage in avoiding competition with other browsers (Cameron, Toit 2007). This competing browsers hypothesis comes with a fair amount of skepticism and suspicion. The main argument against this idea is that an animal of half the height of the giraffe would be able to successfully outcompete other browsers. The fact that the giraffe is more than twice the optimum height is a little disconcerting. This added height causes problems for the giraffe physiologically such as high blood pressure and high energy expenditure causing the giraffe to need a higher nutrient intake (Altwegg 2010). This central problem with the competing browsers hypothesis has led to heavy suspicion among evolutionary biologists for an extended period of time. The latter hypothesis, also known as the necks-for-sex hypothesis, is a fairly recent hypothesis given by Robert Simmons and Lue Scheepers. These were the first biologists to truly question the competitive browsers hypothesis in the year 1996. Simmons and Scheepers denied the competitive browser hypothesis by stating a few “simple” ideas, while hypothesizing about intrasexual selection. They discovered that giraffes, in general, feed from low shrubs, and when doing so, feed faster than when feeding with their necks straight (Scheepers, Simmons 1996). Also, they found that females spend over 50% of their time feeding with their necks bent to eat at lower shrubbery. This would lead one to believe that if feeding high in the canopy allows giraffes to gain a high nutritional advantage, then giraffes would not be eating at low shrubbery with their necks bent. Denying the conventional “competitive browsers” hypothesis, they hypothesized that males fight for females using their necks and armored heads in intrasexual conflicts. This intrasexual conflict is known as necking. Necking occurs when two male giraffes stand side by side and swing their necks at each other in a forceful manner (Scheepers, Simmons 1996). Their research shows that these necking battles arise when male giraffes come across an “estrous female.” These female giraffes give off pheromones that allow males to know when they are ready to mate. This necking is the only form of male fighting found in giraffes and is a prime example of intrasexual selection, a way in which males can prove to females that their genes are of high fitness. Also, they hypothesized that males, on average, tend to have larger skulls and more massive necks than their female counterparts. From extensive research they discovered that male necks were 1.7 times heavier than female necks, and male heads followed the same pattern (Scheepers, Simmons 1996). Also, Simmons and Scheepers learned that selection on giraffes is mainly prominent in the neck region. At the time, this was somewhat shocking evidence. They argued that if natural selection was indeed occurring as a result of the competitive browsers hypothesis, then selection would also lengthen the legs as well as the torso. This selective lengthening of solely the neck region brings up other unnecessary consequences for the physiology of the giraffe, as giraffes often have elevated blood pressure as well as larger hearts (Scheepers, Simmons 1996). The last piece of concrete evidence that Simmons and Scheepers discovered was that the dominance in male giraffes was proportional to neck and head size. They found that males in a dominant position in a population tended to have, on average, larger heads and necks than males in a non-dominant position. This supports the idea that males with heavier necks can outcompete smaller males, thus winning over estrous females (Scheepers, Simmons 1996). Overall, Simmons and Scheepers make a few irrefutable points in stating that male giraffes do indeed use their necks and heads in combat, and giraffes with more massive necks and heads usually gain access to estrous females. After their presentation of research, Simmons and Scheepers’ necks-for-sex hypothesis turned some heads but also drew a number of critics. While this hypothesis seemingly makes a lot of sense, the necks-for-sex hypothesis does not come without controversy and skepticism. Recent research in 2009 by Mitchell, Sittert and Skinner refutes the neck-for-sex hypothesis by arguing that differences in neck size between males and females are a result of the larger final body size of the adult male (Mitchell et al 2009). They attempted to support this idea by dissecting 17 giraffes from southeastern Zimbabwe. They found that female head and neck mass was 3.3 kg and 3.0 kg, respectively, lower than males of the same mass. They also found that head and neck mass formed 12.5% of male bodies, and 10.8% of female bodies (Mitchell et al 2009). They state that this data is insignificant, and does not prove the necks-for-sex hypothesis. They concluded that the difference in head and neck mass was to be expected due to the larger final mass of male giraffes, and therefore intrasexual selection is not the cause of neck elongation in giraffes. These three biologists were not the only ones to refute Simmons and Scheepers hypothesis, as Res Altwegg also critiqued the ideas proposed in Scheepers and Simmons paper. Altwegg argues that in this necks-for-sex hypothesis Simmons and Scheepers do not explicitly explain why females also have long necks (Altwegg 2010). If males use their elongated necks for fighting over estrous females then why do females also have long necks? In another study done to disprove Simmons and Scheepers, Mitchell, Roberts, Sittert, and Skinner studied the heads and necks of over 65 male and 71 female giraffes. They found that the “rate of neck increase” in neck length was very similar in both genders throughout puberty (Mitchell et al 2003). However, they also found that male heads were more heavily armored than female heads, which they do admit could possibly play a role in intrasexual selection (Mitchell et al 2013). It seems fairly obvious at this point that both sides of this issue have their strengths and weaknesses. Proponents of the necks-for-sex hypothesis simply cannot explain why female giraffes have long necks and proponents of the “competing browsers” hypothesis cannot explain why selection did not impose itself on other parts of the giraffe such as the legs or torso. While both hypotheses surely have their shortcomings, they each have central ideas that are irrefutable. It can be concluded that both of these hypotheses play key roles in the origin and preservation of this adaptation in giraffes (Altwegg 2010).

OCTOBER 1st Revisions
Revisions one and two were completed on the Giraffe Wikipedia Talk Page. https://en.wikipedia.org/wiki/Giraffe

A third revision was completed on the page about Adaptation. https://en.wikipedia.org/wiki/Adaptation#Compromise_and_conflict_between_adaptations

First Revision
I think that it is important to further explore these two hypotheses regarding the adaptation that is the neck of the giraffe. It is important to add a counter argument to the "competing browsers" hypothesis by stating the following: There are a number of strong arguments against the competing browsers hypothesis in that giraffe spend fifty percent or more of their time feeding at or below shoulder height. The heavy majority of the time that males are seen foraging with a fully extended neck is when they are in a dominant role among a group of females."

Second Revision
Also, there needs to be some elaboration on the hypothesis regarding the "Necks-for-Sex" hypothesis (and this popular hypothesis name should be explicitly stated in this section). It should be stated that the longer and heavier the neck of the giraffe the more likely the male giraffe is to be dominant in a giraffe population and that long necks are actually selected for by female giraffes during mating season (similar to how peahens select for peacocks with elaborate feathers).

Third Revision
As another example, the long neck of a giraffe is a burden and a blessing. The necks of giraffe can be over eight feet long. This neck can be used for inter-species competition or for foraging on tall trees where shorter herbivores cannot reach. However, as previously stated, there is always a trade-off. This long neck is heavy and it adds to the body mass of a giraffe, so the giraffe needs an abundance of nutrition to provide for this costly adaptation.

Annotations
Adams, J., Badlangana, N. & Manger, P. (2009). The giraffe cervical vertebral column: a heuristic example in understanding evolutionary processes? Zoological Journal of the Linnean Society. Vol. 155. 13 September 2014. This journal excerpt by Badlangana, Adams and Manger attempts to look at the vertebral column of giraffes by studying giraffes of varying ages (calves to full adults). The vertebrae analyzed from these giraffe are compared to the vertebrae of okapi and other camelid species (other animals with elongated necks). The outcome of this study and comparison was that giraffe neck elongation, as well as neck elongation of other camelids, is a direct result of the elongation of the giraffe cervical vertebrae. The second conclusion reached by this study is that this adaptation is a direct result of sexual selection. This is key in identifying this adaptation as a result of evolutionary mechanics.

Altwegg, R. & Simmons, R. (2010). Necks-for-sex or Competing Browsers? Jourmal of Zoology. 13 September 2014. This journal excerpt from Altwegg and Simmons attempts to look at the evolution of the giraffe neck from two different ways. The first view is that these necks of giraffes evolved due to competition with other animals, and giraffes were able to reach higher food, and those with longer necks survived and reproduced. The second theory is that these necks were used for males to combat with and win over a female’s affection. The authors seem to be biased leaning towards the “necks-for-sex” hypothesis and they state that there are some issues with the competing browser hypothesis. This paper is great because it shows competing viewpoints about this evolutionary adaptation.

Cameron, E. & Toit, J. (2007). Tall Giraffes Avoid Competing with Shorter Browsers. The American Naturalist. Vol. 169(1). 13 September 2014. This journal excerpt from Cameron and Toit details the more common hypothesis for the evolution of the elongated giraffe neck. They state a number of facts concerning giraffes and the advantages that giraffes have when feeding on higher tree limbs. They state that giraffes actually ingest more leaf mass per bite when at higher levels of trees than when feeding at lower levels. They essentially conclude that giraffes feed at a higher level because it gives them a survival advantage against smaller predators who are not able to feed at high levels on trees. These authors, are clearly for the “competing browser” hypothesis, and do not mention the necks-for-sex hypothesis explicitly.

Dagg, A. (1971). Giraffa Camelopardalis. Mammalian Species. Vol. 5. 13 September 2014. This piece written by Anne Dagg is fairly straightforward. Basically, what is here is a profile on Giraffa Camelopardalis. This piece will help to adequately discuss giraffe bone structure and the vertebral column that plays such an integral part of giraffe neck elongation. The article also describes giraffe behavior and feeding habits. The article is not biased towards any specific position on giraffe evolution.

Scheepers, L. & Simmons, R. (1996). Sexual Selection in the Evolution of Giraffe. The American Naturalist. Vol. 148(5). 13 September 2014. This journal excerpt from Simmons and Scheepers attempts to explain the elongation of the giraffe neck in terms of sexual selection. They claim that giraffes often feed on low plants during the dry season and that females in general spend over fifty percent of their time feeding while their neck is not nearly fully extended. They suggest that increased neck length in giraffes is a positive attribute in males because female giraffes select for this trait. Also, male giraffes fight with their neck and use their heads as clubs, so the longer the neck, the more likely the male is to win over the female. They claim that sexual selection is often overlooked and that this is a more probable cause than the previous “competing browser” hypothesis. The authors are obviously biased against this hypothesis.