Tuesday, March 17, 2020

Evolutional explanations Essays

Evolutional explanations Essays Evolutional explanations Essay Evolutional explanations Essay The evolutionary explanation, or instinct theory, states that aggression is an adaptive response. This response enables us to obtain resources, defend against attack, eliminate competition for mates and force sexual fidelity from mates. In 1966 Lorenz stated that there were four main drivers behind animal aggression; fear, reproduction, hunger and anger. He also stated that aggression could occur only within a species not across two different species. Lorenz discussed that aggression between two animals is often ritualised. Ritualised aggression itself is aggressive, but little harm actually comes to either animal.This theory is backed up by Morris in 1990, he found that animal disputes show a lot of restraint, this restraint is called an appeasement tactic e.g. dogs show their belly when they feel threatened to stop the opponent from taking the fight any further. The evolutionary approach to aggression states that there are four aims of aggression; to win or control territory, increasing solidarity between males and females, becoming and maintain a dominant role and natural selection through survival of the fittest. There are three main problems with the instinct theory. Firstly, it fails to take into account variations in aggression across individuals and cultures. Secondly, Lorenz compares man to animals and we are not like animals as we have culture to an extent animals do not. The final evaluation point of the instinct theory is that it can be argued that aggression can be learnt socially through social learning theory, not through genes.Infidelity and jealousy is another evolutionary explanation of aggression. Infidelity is having a sexual relationship with someone other than your partner. Jealousy is a state of fear caused by either a real or imagined threat to a person’s status an exclusive sexual partner. Cuckoldry is often the cause of sexual jealousy. Cuckoldry occurs when a woman deceives her male partner into investing into offspring conceived with another man.A main researcher in this area is Young. In 1978 Young asked students to describe how they would react to a jealousy inducing scenario. Men in general said they would become drunk, respond angrily and threaten their rival male. Women on the other hand pretend not to care, cry and try to increase their own attractiveness to get male attention. One major problem with Young’s study is that the participants may have answered differently on the questionnaire to how they would react normally due to social desirability.Another explanation of aggression as an adaptive response is murder. Buss and Duntley (2006) said that humans have evolved adaptations through natural selection to produce what we now call murder. They discussed how if murder is used is determined by four factors; the degree of relatedness between killer and victim, the relative status of killer and victim, the sex of killer and victim and the size and strength of the killer’s and victim’s alliances.In order to evolve as a strategy it must have been associated with greater reproductive success than conflicting strategies. Wilson and Daly in 1985 said that sexual jealousy, lack of resources and threats to male status are all reasons for murder to occur. Wilson and Daly support both their prior study and the study by Buss and Duntley by over viewing the Detroit murders of 1972. They found that the motive behind most of the killings, both killers and victims were unemployed, unmarried and young, low status without a mate. The problem with Buss, Duntley, Wilson and Daly’s research is that is says the act of murder is determined by our evolutionary past and freewill does not come into play, murder could not be committed due to a grudge or hatred is the act is determined.The final explanation of aggression as an adaptive response is group display. There are three levels of group aggression: a crowd, a mob and a riot. A crowd is a lot of people who have gathered into one group very closely, mobs are disorderly crowds and a riot is crowd or gathering which is protesting in a violent manor. Examples of group display fall into three categories; lynch mobs, sport aggression and religious displays. One theory which underpins the idea that group displays are an adaptive response to aggression is the power threat hypothesis. Blalock, in 1967 said that as a minority group grows, the majority group intensifies their efforts to remain dominant.Group displays of solidarity are discrimination against outsiders are more likely when the group feels at risk. Another way groups show aggression is by dehumanising the victim and reducing them into something non human. This makes it easier to carry out aggressive acts e.g. lynching. These aggressive deeds are sometimes made easier for an individual if they de-individuated. When someone is part of a crowd the loose their sense of individuality and therefore will do things they would not normally do. Convergence theory is another theory into group aggression; the group is made up of individuals who all have similar thought processes. Each individual is not influenced by the rest of the group, but all the members behave the same, due to their similar thoughts. Similarly, Contagion theory can also explain group aggression; people are influenced by the way a group acts.The individuals do not need to think similarly, they conform to the behaviour of one bad egg.’ Smelser (1963) argued that social life and its processes affect how individuals behave. This is weakness of the evolutionary theory; aggression is not only affected by our genes it is also affected by our social learning and environment. Smelser also argued that six things are necessary for a social movement to emerge. Structural conduct and if people realise their society has a problem, if society fails to meet expectation and deprives the people, growth and spread of an explanation, if one event triggers a reaction from a crowd, mobilisation for action where people distribute information about a cause and finally a lack of social control leads to a protesting crowd.In conclusion, the instinct theory can explain aggression; the only problem is it doesn’t take into account factors such as culture and it completely ignore the fact that we could learn to be aggressive through social learning. So overall a mixture of different explanations is needed to explain aggression.

Sunday, March 1, 2020

Introduction to Bipedal Locomotion

Introduction to Bipedal Locomotion Bipedal locomotion refers to walking on two legs in an upright position, and the only animal to do that all the time is the modern human. Our ancestor primates lived in trees and rarely set foot on the ground; our ancestor hominins moved out of those trees and lived primarily in the savannas. Walking upright all the time is thought to have been an evolutionary step forward if you will, and one of the hallmarks of being human. Scholars have often argued that walking erect is an enormous advantage. Walking erect improves communication, allows visual access to farther distances, and changes throwing behaviors. By walking upright, a hominins hands are freed to do all sorts of things, from holding babies to making stone tools to throwing weapons. American neuroscientist Robert Provine has argued that sustained voiced laughter, a trait which greatly facilitates social interactions, is only possible in bipeds because the respiration system is freed to do that in an upright position. Evidence for Bipedal Locomotion There are four main ways scholars have used to figure out whether a particular ancient hominin is primarily living in the trees or walking upright: ancient skeletal foot construction, other bone configurations above the foot, footprints of those hominins, and dietary evidence from stable isotopes. The best of these, of course, is foot construction: unfortunately, ancient ancestral bones are difficult to find under any circumstances, and foot bones are very rare indeed. Foot structures associated with bipedal locomotion include a plantar rigidity- flat foot- which means the sole stays flat from step to step. Secondly, hominins that walk on the earth generally have shorter toes than hominins who live in trees. Much of this was learned from the discovery of a nearly complete Ardipithecus ramidus, an ancestor of ours who apparently walked upright sometimes, some 4.4 million years ago. Skeletal constructions above the feet are slightly more common, and scholars have looked at the configurations of the spine, the tilt, and structure of the pelvis, and the way the femur fits into the pelvis to make assumptions about a hominins ability to walk upright. Footprints and Diet Footprints are also rare, but when they are found in a sequence, they hold evidence that reflects the gait, length of stride, and weight transfer during walking. Footprint sites include Laetoli in Tanzania (3.5-3.8 million years ago, probably Australopithecus afarensis; Ileret (1.5 million years ago) and GaJi10 in Kenya, both likely Homo erectus; the Devils Footprints in Italy, H. heidelbergensis about 345,000 years ago; and Langebaan Lagoon in South Africa, early modern humans, 117,000 years ago. Finally, a case has been made that diet infers environment: if a particular hominin ate a lot of grasses rather than fruit from trees, it is likely the hominin lived primarily in grassed savannas. That can be determined through stable isotope analysis. Earliest Bipedalism So far, the earliest known bipedal locomotor was Ardipithecus ramidus, who sometimes- but not always- walked on two legs 4.4 million years ago. Fulltime bipedalism is currently thought to have been achieved by Australopithecus, the type fossil of which is the famous Lucy, approximately 3.5 million years ago. Biologists have argued that foot and ankle bones changed when our primate ancestors came down from the trees, and that after that evolutionary step, we lost the facility to regularly climb trees without the aid of tools or support systems. However, a 2012 study by human evolutionary biologist Vivek Venkataraman and colleagues points out that there are some modern humans who do regularly and quite successfully climb tall trees, in pursuit of honey, fruit, and game. Climbing Trees and Bipedal Locomotion Venkataraman and his colleagues investigated behaviors and anatomical leg structures of two modern-day groups in Uganda: the Twa hunter-gatherers and Bakiga agriculturalists, who have coexisted in Uganda for several centuries. The scholars filmed the Twa climbing trees and used movie stills to capture and measure how much their feet flexed while tree-climbing. They found that although the bony structure of the feet is identical in both groups, there is a difference in the flexibility and length of soft tissue fibers in the feet of people who could climb trees with ease compared with those who cannot. The flexibility that allows people to climb trees only involves soft tissue, not the bones themselves. Venkataraman and colleagues caution that the foot and ankle construction of Australopithecus, for example, does not rule out tree-climbing, even though it does allow upright bipedal locomotion.   Sources Been, Ella, et al. Morphology and Function of the Lumbar Spine of the Kebara 2 Neandertal. American Journal of Physical Anthropology 142.4 (2010): 549-57. Print. Crompton, Robin H., et al. Human-Like External Function of the Foot, and Fully Upright Gait, Confirmed in the 3.66 Million Year Old Laetoli Hominin Footprints by Topographic Statistics, Experimental Footprint-Formation and Computer Simulation. Journal of The Royal Society Interface 9.69 (2012): 707-19. Print. DeSilva, Jeremy M., and Zachary J. Throckmorton. Lucys Flat Feet: The Relationship between the Ankle and Rearfoot Arching in Early Hominins. PLoS ONE 5.12 (2011): e14432. Print. Haeusler, Martin, Regula Schiess, and Thomas Boeni. New Vertebral and Rib Material Point to Modern Bauplan of the Nariokotome Homo Erectus Skeleton. Journal of Human Evolution 61.5 (2011): 575-82. Print. Harcourt-Smith, William E. H. Origin of Bipedal Locomotion. Handbook of Paleoanthropology. Eds. Henke, Winfried, and Ian Tattersall. Berlin, Heidelberg: Springer Berlin Heidelberg, 2015. 1919-59. Print. Huseynov, Alik, et al. Developmental Evidence for Obstetric Adaptation of the Human Female Pelvis. Proceedings of the National Academy of Sciences 113.19 (2016): 5227-32. Print. Lipfert, Susanne W., et al. A Model-Experiment Comparison of System Dynamics for Human Walking and Running. Journal of Theoretical Biology 292.Supplement C (2012): 11-17. Print. Mitteroecker, Philipp, and Barbara Fischer. Adult Pelvic Shape Change Is an Evolutionary Side Effect. Proceedings of the National Academy of Sciences 113.26 (2016): E3596-E96. Print. Provine, Robert R. Laughter as an Approach to Vocal Evolution: The Bipedal Theory. Psychonomic Bulletin Review 24.1 (2017): 238-44. Print. Raichlen, David A., et al. Laetoli Footprints Preserve Earliest Direct Evidence of Human-Like Bipedal Biomechanics. PLoS ONE 5.3 (2010): e9769. Print. Venkataraman, Vivek V., Thomas S. Kraft, and Nathaniel J. Dominy. Tree Climbing and Human Evolution. Proceedings of the National Academy of Sciences (2012). Print. Ward, Carol V., William H. Kimbel, and Donald C. Johanson. Complete Fourth Metatarsal Andarches in the Foot of Australopithecus Afarensis. Science 331 (2011): 750-53. Print. Winder, Isabelle C., et al. Complex Topography and Human Evolution: The Missing Link. Antiquity 87 (2013): 333-49. Print.