The Concepts of Evolution - Essay Example

?Introduction The concepts of evolution have altered not only according to specific needs of various species but also because of responses to the surrounding environment. This has altered the way in which many species continue to function as well as what the relationship to the environment is. The use of bipedality is one of the alternatives which have evolved through time among homo sapiens. This is directly attributed to not only needs for maneuvering and basic functions. Many theories also show that bipedality is related directly to the climate change and the stress which this caused on the human body. The evolution into bipedality because of climate change and the alterations which have occurred in various regions of the world all provide support which shows that environmental stimulation has also regulated the evolution of men. Environmental Stimuli in Hominids There are several theories which show that the environmental stimulation in an environment also affects the way in which ontogeny, organismal adaptation and spectation occur throughout time. Most of the adaptation which has been noted with evolution is from the ideal that there is a response to the needs of a specific species as well as the requirements to survive within a given region. While the adaptation is noted as a component of evolution, many have disregarded the environmental stimuli and the way in which this has altered the functions and evolutionary changes. The concept of neo-Darwinism is one of the main approaches to this. According to Darwin, all species would respond with evolution by competition within the species and with the need to survive. In the neo-Darwinism thought process, there is a link to the understanding that the physical alterations in a species occur specifically because there is the need to adapt to various elements in the surroundings, such as the environment (Vrba, 1442). While there are several links to physical alterations and dimensions related to why evolution occurs, adaptation to the environment is one of the considerations which has evidence in relation to evolution. This is also known as allopatic speciation, which fragments and segments species into various populations. When looking at these populations, it can be seen that the original homo sapiens were fragmented into one sector of the world. The environmental tables within these regions then included adaptation to components such as food intake, temperature, vegetation cover, light intensity and the climatic and tectonic changes. When a species adapted from one region, also known as the stenobiomic region to a eurybiomic, or across biome region, changes would have to be made in regards to the various elements of the environment. Adaptation to the environment, such as different types of water, responses from the skin because of the light and changing behaviors from the climate then become a part of the natural adaptation process, specifically from the environmental stimulus which has occurred (Vrda, 1446). Evolution Into Bipedality While environmental stimuli shows a direct relationship to the anatomical features of hominids and the potential adaptations which are a part of the evolution. According to the adaptability hypothesis, the evolution of individuals is based on the need to endure environmental fluctuations, specifically as different species began to move into different regions of the world. This is combined with the theory of the turnover hypothesis, which states that the adaptability to different environments occurred over a longer period of time and evolved specifically as the environment began to change. The evidence of this occurs in the African Pliocene which shows fossils as evidence of older species of hominids that are now extinct. The body shape, looks of the species and the physical applications draw evidence to the climate alterations and the functions of the society, such as stone making, which no longer fit into the environment. The timing that leads to the specific evidence of the species relates directly to features that show how the environmental alterations in the climate also led to the extinction of specific features and species which didn’t adapt to the climate shifts (Potts, 27). The first evidence of bipedality was noted not only in the environmental shifts of the human fossils, but also is found in the evolution of chimpanzees and the bipedal motions which occur when they are eating smaller fruits from open forest trees. The bipedal features are noted only when the chimpanzees need to stand to reach the fruit or when there is an overhead branch. This evidence shows a direct relationship to the environmental stimuli of feeding among the chimpanzees. The low – frequency bipedalism which is in chimpanzees is a sign that relates to other types of features which show that adaptation to the environment also means altering the locomotive features that are associated with different species (Hunt, 183). It is the same concept as noted from the chimpanzees that also relates to the anatomy of other species and the need to adapt to the environment through the several surroundings that changed through time. There are several implications which show that early human species were in environmental areas that consisted of wet lands or subterranean areas, as well as open forests. Each of these areas required bipedalism for a variety of reasons. The first was to reduce energy consumption while gathering food in the open areas, such as standing to gather fruit. The development included the wider hips which could hold the energy and a neck which was thinner. This was combined with joint reaction forces, which assisted in faster movements and muscular support that decreased the stress on the body. This led to fatigue in the bodies, specifically which was reduced because of the muscle tissue which could be used for more power and which allowed the energy of individuals to become more powerful. The upper body anatomy was then able to be used for easier climbing, adaptation to flexibility in the back and the ability to move across longer distances in a shorter period of time (Hunt, 190-194). Climate Change and Bipedality The mobility which was required for different regions and the environmental stimuli which was linked directly to the hominids then links to other factors which could have shifted the movement of various species. Climate change and climate stress are factors which can be added into the reasons for evolution into bipedality. The climatic forcing model is one of the indications which prove that mobility altered specifically because of environmental changes which were occurring. This was first seen with the African bovid speciation, which experienced oxygen isotope curves and changes in the climate from deep sea drilling. The result was a decline in temperature in the region, specifically which changed the habitat, temperature, rainfall and vegetation. As a result, the hominid species had to change the behaviors to match with the environment for food and other basic needs within the environment (Foley, 275). There are two components which make a difference in the climate change and the effects which it has on hominids. The first is the changes over time, such as a decrease or increase in temperature. The second is climatic stress, which consists of sudden changes that change a species in a different direction because of the sudden fluctuations. It has been found that sudden climatic stresses and changes can lead to the extinction of species because of the drastic results that are found. However, the changes which occur over time have a negative relationship and allow the species to continue to evolve and develop in relation to the environmental stimuli which occurs. These two factors then lead to the species response, which creates diversification in the mobility of species and ways in which the specie can create a sense of stability with the temperature, changes in the environment and alterations needed for survival within a given region (Foley, 286). The proof of climatic stress and changes in the environment leading to evolutionary changes then lead to proof of bipedality as a response to the environment. One of the known problems of hominids is from the lack of hair that can protect against higher or lower temperatures, specifically which can lead to hyperthermia or induced muscular activity. This is combined with the lower body temperature that is located around the brain because of the larger mass size in this area. The natural physical presence of hominids then leads to the need to create a way to disperse heat in a balanced manner. The use of bipedality allows cooling of the brain while regulating problems such as hyperthermia and body heat. When extreme temperatures arise, the body can then naturally respond by regulating the distribution of heat or cooling while having a thermoregulatory function in various climates. The result is the ability to respond to heat related stress or extremely cold temperatures while building extra layers of muscle tissue and fat underneath the skin to assist with the regulation of temperature (Wheeler, 92-93). These attributes of bipedality show a direct link to the temperature of climates and how this links to the evolution of the species because of physical attributes. The climate change which is regulated by temperature also links to changes such as tectonic changes, global climate transitions and local variations from orbital forcing. Regional tectonics is known to go back to the evolution of species in Africa, specifically which created thresholds between cooling and heating over a longer period of time. This led to extreme periods of both wet and dry in the region while leading to variability in lakes, followed by rifts which were created in various areas. To adapt to the rapid shifts and climatic stress occurring, there was the need to move through the climatic variability. Hominids were known to travel longer distances and to remain in open areas where it was easier to find food and to adapt to the temperatures. The need to have more strength in the legs and to move at a faster pace was a part of this adaptation, specifically which allowed the continuous climate changes to fit with the movements of the species through various regions. In this way, there was the ability for the climate change to remain easier to adapt to while allowing food, water and other elements to become adaptable in various regions (Maslin, Christensen, 443). The evidence which leads to the climate changes and stresses that related to bipedality is directly linked to the diversity of species and the adaptation into various regions. The ancestors of Humo Rudolfensis, Homo Habilis, Australopithecus Aferensis and Australopithecus Africanus are some of the hominids which display the changes associated with various regions. The amount of bipedality in each of these species relates to the ways in which food is gathered, types of spaces that each lives in and the amount of mobility that is required for adaptation into the given area. It is noted that the habitats which are more open, such as wetlands, grasslands and open forest, have direct relationships to the amount of bipedality that is used. When the forests are dense, there is the need to use different types of locomotion. The climatic stresses in the denser areas were also known to not have as much variety as the open spaces, as the tectonic shifts and temperature alterations were protected in these regions. The difference between these species and the use of bipedality shows how the climatic stresses in various regions evolved because of the need to have more ways of gathering food, moving and regulating temperatures in the body (Bromage, Schrenk, 109). An example of the regional changes between spaces and the relationship to bipedality can be seen with the pan-African approach and the climate differences that evolved through time. Fossil records indicate both that there were large areas that led to movement of species while locomotion developed over a longer period of time in response to both the movement and climatic changes. The evolution relates directly to the geographical megastructure where rifting began and developed islands. Before this, there were large rainforests and volcanic activities that were shaping the land. The rain shaded areas have led to the findings of Miocene Sahelanthropus, hominids which lived in the rift area of Eastern Africa. These species were known to adapt to knuckle walking, as opposed to their predecessors in the rainforests, which were adapted to walking on all fours. This led to the next phase of cooling in Africa, which changed the rainforests into a rise of plateaus in the region. This altered from rainforests to woodlands and then into seasonal forests. Each of these habitats also relate to changes in fossil species, such as the absence of the Miocene in the rainforests and a correlation which began to turn over into bipedalism as the plateaus and seasonal forests began to shift with the climate. This links back to the turnover theory, which shows that bipedalism developed over time and related directly to the environmental applications. The need for easier mobility, saving energy and the natural resources moving through the body then became the main areas of evolution among the species (Schrenk et al, 116). The changes in climate and the need to find natural resources also leads to the changes among hominid species in regards to the climate. As the densely populated areas, such as the rainforests and seasonal forests moved into terrains, there were also responses in relation to the body structure. A loss of hair from the heat occurred while darker colors in hominids began to appear. There was also the need to keep water retention because of the heat and cooling systems which were now exposed to the hominid species. The bipedality was able to distribute these systems while creating a way of remaining protected from the sun in most areas of the body. This is known as a savannah adaptation, specifically because it allowed the response of hominids to be based on the open, heated areas, specifically which required more water and the ability to have protection against the heated sun that wasn’t covered by the denser environmental areas. The physiological accommodations from the stress related aspects then show a direct relationship to the environmental shifts and the way in which evolution began to adapt according to the climatic changes (Steele, 147). When looking at the physiology of hominids, it can be seen that there was a transition from the quadrupedalism stance and into the bipedal stance. The biomechanical and physiological characteristics that are associated with this are based on the functions of the joints and limbs, known as the inverted-pendulum model. The physiological attributes relate to mammals having the capability of having faster walking speeds, low stride frequencies, low vertical forces and high impact shock ratios. Quadrupedalism; however, suggests the need to climb because of the joints which are less stable. This shows that there is a relationship between the environmental shifts and the movement into bipedalism, specifically to cover larger, open areas. The physiology also points to a diversity of species which were able to remain in more dense areas, such as rainforests, specifically which needed the climbing abilities more in the physiology of running and walking faster (Schmitt, 1437). The stance which was taken can be furthered with the physiological changes according to the joint reactions and alterations which occurred with bipedalism. The two main changes which occurred were the bent hip and bent knee used for walking. These had more flexibility and the ability to take longer and faster strides then with other stances. The change is known as dynamic modeling, which is able to transform the energy used when in both potential and kinetic states. When walking or running in three different positions, the bent hip and bent knee has the same implications, which allows the energy transformation to be preserved when going through various areas. It also leads to less stress throughout the body, specifically with muscle tissues and joints that are associated with the body. When being in densely populated environmental areas, the bipedal reactions would have been a disadvantage for finding fruit, moving through distance and responding to environmental needs. However, the movement into rifts and open terrains indicate that the bent hip, bent knee physiology serve a better purpose in preserving energy and going through longer distances (Wang et al, 563). The physiological changes, alterations in the environment and the finding of a diverse set of species all point to the climate changes and stresses also altering into the evolution of bipedalism. The physiological aspects included the need to walk across long distances, joint reflexes which were more convenient for faster movements, preservation of energy and the ability to balance temperatures in various regions. This was combined with the need to respond to the environment, specifically with finding food in various regions, responding to the tectonic shifts which were occurring and responding with specific temperate alterations and survival needs. The environment, climate alterations and stresses all point to bipedalism contributing as a main factor to the evolution of hominids in open regions specifically in response to the climate. Debates Against Environment and Evolution The concept of the environment and evolution links to other reasons which may have caused the changes to bipedalism. One of the noted differences is from the earlier bipeds, Africanus Afarensis and Africanus Africanus. The difference between these two bipeds is known to be nearly identical; however, there the dental and cranial anatomy differs. The structural changes don’t indicate differences because of the bipedal attributes or environmental changes, as both evolved in the same region. However, the anatomy also implies that there is a direct relationship not only to the environmental concepts but to the natural selection which occurred. Each of the species may have adapted to the environment in different ways, such as by eating a different type of food or through locomotive behaviors which implied survival of the species. In this instance, the small differences between the two imply that the locomotive behaviors were based on structural adaptations and natural selection. While the changes in the environment may have also been a factor, the other potential needs for the species can’t be disregarded in the growth into the bipedal nature of both species because of the slight alterations of both (McHenry, 177). Another debate against the climatic changes being a basis for the locomotive behaviors is based on the physiological selective pressures which were a part of the earlier hominid species. The movement into bipedalism doesn’t account for other hominid species which didn’t adapt to this or which only use bipedal attributes at selective times. Many archeologists suggest that the physiological selective pressures are the main ways in which adaptability has occurred, specifically with the need to adapt to the environment which already existed. Some physiological pressures included the need to visualize food from different angles and the need to overcome barriers in terms of carrying and distributing among species. Food piles, visual barriers and foraging structures are the main changes which changed the physiology and led to this adaptability. While there is a link to the climate, the association with bipedal attributes is related more to the physiological structure adapting to specific behaviors, many which were not dependent on bipedalism, but instead behaviors within the environment (Videan, McGrew, 184). The relationship to the physiology of hominids leads to the increasing debate. There are several archeologists that have pointed to fossils which have altered bone structures, joint width and structures within various bones, such as the feet. While these different locomotive features are based on adaptation to various regions, it is also noted that several diverse fossils are often found in the same region. Some of the hominid structures, specifically in the feet, are inflexible and are based on the need to climb while others adapted to the need to move across the floors of the various regions. These species are seen in the same climate, even though the structure of the bones is different and led to the bipedalism. This shows that the climate, while remaining a factor, may have not been as important as physiological differences and the needs of various species. The diversity in species may have directly related to changes in food patterns and behavioral habitats. The diversity in various locations then shows that physiological differences are behavioral, rather than processed through the pressures of the environment (Harcourt, Aiello, 16). Conclusion The concept of bipedalism and the environment is one which indicates that the evolution of hominids is based on the climatic fluctuations and pressures. When looking at the physiology of earlier species who adapted bipedalism, it can be seen that there was consistency in the need to conserve energy, balance the temperatures in the body and to remain locomotive through terrains and open spaces. The climatic changes related to this, specifically which show a direct link to the alterations in the environment and the way that bipedalism evolved for temperature needs, energy conservation and the need to gather food and water. The shifts in the environment, ranging from tectonic alterations to regression of densely populated environmental areas to open spaces show the same pattern and consistency in physiological changes to bipedalism for the purpose of surviving in the given region. While there are strong relationships to the environment, many archeologists disagree with the climatic pressures as the main reason for evolution. The diversity of species in various regions as well as the adaptability to the same region shows that the physiological differences may have been the main approach to the evolution which occurred through time. This is based on the diverse species that are located in one region, some which have bone structures to indicate the only difference was in the food which was chosen by the species. This relates to the process of natural selection in which each species adapts to a different region based on specific needs and to remain competitive with other species for survival. While the environment is still a factor in these physiological differences, it becomes secondary to the nature and behavior of species. Even with these alternative theories, it can be seen that the climate forces alter the behaviors and physiological differences in the evolution of hominids to bipedalism indicating that the natural fluctuations in the climate also alter the natural tendencies of evolution over time of a given species. Works Cited Bromage, Timothy, Friedemann Schrenk. “Biogeographic and Climatic Basis for a Narrative of Early Hominid Evolution.” Journal of Human Evolution 28 (1), 1995. Foley, R.A. “Speciation, Extinction and Climatic Change in Hominid Evolution.” Journal of Human Evolution (26), 1994. Harcourt, WEH, LC Aiello. “Fossils, Feet and the Evolution of Human Bipedal Locomotion.” Journal of Anatomy 16 (3), 2004. Hunt, Kevin. “The Evolution of Human Bipedality: Ecology and Functional Morphology.” Journal of Human Evolution (26), 1994. Maslin, Mark, Beth Christensen. “Tectonnics, Orbital Forcing, Global Climate Change, and Human Evolution in Africa: Introduction to the African Paleoclimate Special Volume.” Journal of Human Evolution 53 (5), 2007. McHenry, Henry. “The First Bipeds: A Comparison of the A. Afernsis and A. Africanus Postcranium and Implications for the Evolution of Bipedalism.” Journal of Human Evolution 15 (3), 1986. Potts, Richard. “Environmental Hypothesis of Pilocene Human Evolution.” National Museum of Natural History. Schmitt, D. “Insights into Evolution of Human Bipedalism from Experimental Studies of Humans and Other Primates.” Journal of Exploratory Biology 206 (9), 2003. Schrenk, F, Oliver Sandrock, Ottmar Kullmer. “An Open Source Perspective of Earliest Hominid Species.” Collaborative Anthropology 28 (2), 2004. Steele, James. “Climate and Human Progress.” Cambridge Archeological Journal (4), 1994. Videan, Elaine, WC McGrew. “Bipedality in Chimpanzee and Bonobo: Testing Hypothesis on the Evolution of Bipedalism.” American Journal of Physical Anthropology 118 (2), 2002. Vrba, Elizabeth. “Role of Environmental Stimuli in Hominid Origins.” Wang, WJ, RH Crompton, y Li, MM Gunther. « Energy Transformation During Erect and Bent – Hip, Bent – Knee Walking by Humans with Implications for the Evolution of Bipedalism.” Journal of Human Evolution 44 (5), 2003. Wheeler, A. “The Evolution of Bipedality and Loss of Functional Body Hair in Hominoids.” Journal of Human Evolution (13), 1984. Read More