The Evolution Of The African Elephants Trunk - Research Paper Example

The Evolution Of The African Elephant’s Trunk INTRODUCTION The trunk is one of the most appealing morphological traits of an elephant. The trunk is a highly flexible and well-built organ that the elephant uses excellently. With the remaining three species having relatively different physical and adaptive functions, the same accounts can predict the past and future of this evolutionary trend. The following paper discusses and analyzes the morphological natures of the elephant trunk, several evolutionary hypotheses that explain these natures, and the feasibility of any predictions these theories make. This paper will focus on the African elephant. FEATURES OF THE AFRICAN ELEPHANT TRUNK Essentially, the elephant trunk is an elongated nose used for respiratory, olfactory, trumpeting, containment, grasping, offensive, and communication purposes (Hughes 8). Evidence that may suggest these roles are the African elephant trunk’s physical structure and composition. The trunk of the African elephant comprises of a nose and upper lip. At the tip, the trunk breaks into two “fingers” unlike its closely related species, the Asian elephant, which has only one “finger” (Neubauer 128). Even though the trunk partially comprises of the nose, the African elephant does not have a nasal bone or any bone for that matter. The trunk is made up of fat, blood vessels, numerous nerve endings, and 8 main muscles on each side, which break up into 150,000 fascicles (Ungar 97). The trunk of the African elephant can weigh as much as 400 pounds and reach lengths of 7 feet (Moss, Croze, and Lee 103). Two nostrils exist at the tip of the trunk, which is evidence for breathing passages. African elephants use their trunks for containment purposes with highly porous and flexible muscles serving as evidence (Hughes 8). The trunk of the African elephant is so large and porous; it can hold up to 8 liters of water at a go. The African elephant draws water up its trunk, curls, puts it into mouth, and lets the water pour into the mouth by slanting the head backwards (Richard and Bates 3). Grasping is evident in the African elephant through the clutching of items such as logs and forage using the two “fingers” (Neubauer 128). The trunk acts as a communication tool that the African elephant uses to ward off other elephants or cue its mood (Moss, Croze, and Lee 108). Lastly, the African elephant uses the trunk’s many tough muscles to attack other animals or elephants by punching or shoving (Cristoffer and Peres 1360). However, the African elephant rarely uses its trunk offensively and seriously as tusks exclusively serve offensive and defensive purposes. Phylogenetic Perspective. The African elephant trunk is an interesting example of the focus of abilities and adaptive roles across the elephant species. Commonness of Traits. Both the African and Asian elephant species have trunks with different tips. Other than the differently “fingered” tips, the trunks of the Asian and African elephants have and serve pretty much the same traits and adaptive functions respectively (Abramson 2014). EVOLUTION OF THE AFRICAN ELEPHANT TRUNK The African elephant evolved its trunk around 10 million years ago with its main ancestors, the Primelephas and Paenungulata, being the original bearer of this trunk. The Primelephas evolved today’s African elephant trunk during the Miocene epoch in the forest savannahs of East Africa, which was shared by the mammoth (Sukumar 19). The diversion of the “fingered” tips between the African and Asian elephants occurred around 1.5 million years ago (Kingdon, Happold, Butynski, Hoffmann, Happold, and Kalina 787). Discussion and Comparison of Hypotheses. Charles Darwin’s theory of evolution is the most popular hypothesis for the adaptive function of the African elephant’s trunk. According to Darwin, natural selection occurs when less suitably adapted organisms die off and more suitably adapted survive (Ungar 109). The Paenungulata and Primelephas were varied in the sense that they had both short and long trunks. When there were food and water shortages, elephants with short trunks perished since they could not reach these resources. On the other hand, elephants with long trunks reached the scarce resources and passed on their genes to future generations. Gradually, the African elephant evolved a long trunk. From this hypothesis, the purposes of containing, grasping, and smelling are evident (Sukumar 45). A second alternative theory by pulmonary physiologist John B. West applies more recent study findings to argue that the African elephant trunk evolved to suit respiratory purposes. West said elephants overall evolved elongated noses to allow them to breathe while submerged in water (Mayell 2002). This hypothesis adds that snorkeling was the original, prime reason for evolving a trunk although its adaptive functions have diversified widely over millions of years. This hypothesis also resonates with Darwin’s evolution theory since the survival of the African elephant clearly depended on fitness to breathe well while under water. The main evidence for West’s hypothesis lies in the structure of the African elephant’s lungs. Between 1960 and 1961, West found out that the lungs of the African elephant have “pleural cavity” full of “connective tissue,” which only evolved in this mammal (Mayell 2002). Pleural cavity allows the African elephant to endure the great differences in pressure on top of and under water without bursting blood capillaries within the walls of the lungs. West uses recent, strong evidence of elephant ancestors being fully aquatic animals. Similarly, currently close relatives of the African elephant, the manatees and dugongs, are aquatic. More evidence for this hypothesis is the African elephant’s current, excellent swimming abilities (Abramson 2014). A third alternative hypothesis by paleontologist William Sanders accounts for the African elephant trunk as an outgrowth of adaptation (Handwerk 2008). Unlike West, Sanders provides new evidence that the Moeritherium, an overall ancestor of the elephant, was not fully aquatic. Instead, Moeritherium was relatively similar to the hippo or sea cow in their ways of life and adaption. At the same time, Sanders warns against presuming the African elephant’s ancestors were aquatic, making the “snorkel” adaptation is wrong (Handwerk 2008). PREDICTION Darwin’s evolution hypothesis made the most predictions about the African elephant trunk. First, Darwin predicted clearly observable designs in terms of the length of the ancestors of the African elephant and the modern species (Abramson 2014). Secondly, Darwin did not find it relevant whether he could better predict the trunk of the African elephant through competition, natural selection, or parsimonious behavior (Richard and Bates 8). Third, the natural selection theory predicted there was no one-on-one relationship between the length of the trunk and other related features such as the elephant’s diet or body size. This prediction clearly focuses on the trunk as a trait and not by means of inclusion. West’s hypothesis of snorkeling predicted that early Proboscidea spent prolonged periods submerged in water (Mayell 2002). During these submersions, Proboscidea used their trunks as snorkels to respire. Although Proboscidea shifted to terrestrial habitats over the years, the respiratory function remained as an adaption. This prediction does not account for the length of the African elephant because the waters this species spends a lot of time in immersion are usually not deep enough to pose serious risks. However, West mentions the fact that African elephants today can spend hours fully immersed in water with the trunk exposed on the surface for breathing. Sanders’ hypothesis predicts that the Moeritherium had an elongated snout and not a true trunk. According to Sanders’s hypothesis, the first proboscideans did not have elongated noses and the evolution of the trunk is related more to hypertrophy or extension of the tusks and eating adaptations on land than breathing (Handwerk 2008). Oxford researcher Liu supports Sanders’ hypothesis by stating that studying the African elephant’s dentition can shed light on the history of the trunk. This is because teeth unveil an animal’s feeding habits (Ungar 107). In this case, Liu says researching the separation of the Sirenians from their relatives can determine whether the African elephant trunk evolved on land or in water (Handwerk 2008). TESTING THE HYPOTHESES Scientific studies that tested Darwin’s hypothesis are not stipulated. The few studies that exist cover the entire natural selection and evolution hypotheses without focusing on the trunk of any elephant species. Research works testing West and Sanders are limited to accounts for adaptation only. Quantitative methods of research design are crucial for testing Darwin’s hypotheses. The notion that natural selection has conceptual issues fails simple testing. One can use experiential methods to project changes in Darwin’s strong hypothetical grounds by means of fitness in phylogenetics. Results that could refute this theory would dismiss its description of the African elephant trunk as a trait of the species and not adaptive function. The type of data relevant for testing Sanders and West’s hypotheses is qualitative. The relationship between the length of the trunk and scarcity of resources is inclusive since later researchers. For instance, West frequently disregards many adaptive traits to seemingly random chance that are too obvious or have contemporary morphological correspondences (Mayell 2002). In this case, West considers the African elephant’s current ability to snorkel proof of the trunk’s snorkeling use by ancestors and reason for evolving a lengthier nose with two “fingers” (Cristoffer and Peres 1368). CONCLUSION The trunk evolved to have an extremely important role in an elephant’s life in terms of survival and leisure purposes. The elephant trunk evolved to carry out these purposes differently when the elephant genus diverged from the main ancestral branch millions of years ago. In the process, the trunk took on various roles and functions, some of which persisted to the remaining species today. Researchers and biologists Charles Darwin, John B. West, and William Sanders have developed various evolutionary accounts for the current adaptive functions and traits of the elephant’s trunk. Works Cited Abramson, Jordan Hayley. The Elephant's Trunk. 2011. Science in Our World: Certainty and Controversy. Web. 15 Dec. 2014. Byrne Richard W. and Lucy A. Bates. “Elephant cognition in primate perspective.” Elephant Cognition 4 (2009): 1-15. Cristoffer, Cris and Carlos A. Peres. “Elephants versus butterflies: the ecological role of large herbivores in the evolutionary history of two tropical worlds.” Journal of Biogeography, 30 (2003): 1357–1380. Handwerk, Brian. Ancient Elephant Ancestor Lived in Water, Study Finds. 2008. National Geographic News. Web. 15 Dec. 2014. Hughes, Jonnie. On the Origin of Tepees: The Evolution of Ideas (and Ourselves). New York, NY: Simon and Schuster, 2012. Print. Kingdon, Jonathan, David Happold, Thomas Butynski, Michael Hoffmann, Meredith Happold, and Jan Kalina. Mammals of Africa, Volumes 1-6. London: A&C Black, 2013. Print. Mayell, Hillary. Snorkeling Elephants and the Secrets of Breathing. 2002. National Geographic News. Web. 15 Dec. 2014. Moss, Cynthia J., Harvey Croze, and Phyllis C. Lee. The Amboseli Elephants: A Long-Term Perspective on a Long-Lived Mammal. Detroit: University of Chicago Press, 2011. Print. Neubauer, Raymond L. Evolution and the Emergent Self: The Rise of Complexity and Behavioral Versatility in Nature. Berkley, CA: Columbia University Press, 2013. Print. Sukumar, R. The Living Elephants: Evolutionary Ecology, Behaviour, and Conservation. London: Oxford University Press, 2003. Print. Ungar, Peter S. Mammal Teeth: Origin, Evolution, and Diversity. New York: JHU Press, 2010. Print. Appendix Charles Darwin John B. West William Sanders 1. When there were food and water shortages, elephants with short trunks perished since they could not reach these resources. The African elephant trunk evolved to suit respiratory purposes. The African elephant trunk was an outgrowth of adaptation 2. Elephants with long trunks reached the scarce resources and passed on their genes to future generations. Elephants overall evolved elongated noses to allow them to breathe while submerged in water. Sanders provides new evidence that the Moeritherium, an overall ancestor of the elephant, was not fully aquatic. 3. Gradually, the African elephant evolved a long trunk. From this hypothesis, the purposes of containing, grasping, and smelling are evident. Snorkeling was the original, prime reason for evolving a trunk although its adaptive functions have diversified widely over millions of years. The African elephant’s ancestors were not aquatic, making the “snorkel” adaptation is wrong 4. There were clearly observable designs in terms of the length of the ancestors of the African elephant and the modern species. Evidence lies in the structure of the African elephant’s lungs. Pleural cavity allows the African elephant to endure the great differences in pressure on top of and under water without bursting blood capillaries within the walls of the lungs. Moeritherium was relatively similar to the hippo or sea cow in their ways of life and adaption Read More