Homosexual Orientation in Males--论文代写范文精选

一些假设基于过去的研究，性取向,通常归类为异性恋,同性恋,双性恋,但关于人类性行为，当代科学范式是基于这样一个假设，异性恋取向是常态。下面的essay代写范文进行详述。

Abstract 
Evolutionary theory proposes that adaptive traits are reproduced more successfully than maladaptive traits. Accordingly, natural selection should favor heterosexuality as it facilitates reproduction and the propagation of genes. However, the question becomes, what has maintained homosexuality in a small but consistent percentage of the human population? Research into the evolutionary and hormonal factors associated with a homosexual orientation have yielded provocative but inconsistent results. It also suggests that human sexual orientation, and in particular homosexual orientation, is too complex to be described by one simple model or a single research discipline. The current paper treads a new path and emphasizes an integrative approach for the understanding of homosexuality. The authors examine the combined effects of evolutionary factors and neurohormonal processes on the development of a homosexual orientation. It is suggested that research into the topic could benefi t from an examination of and change in some of the assumptions upon which much past research has been based.

Introduction 
Sexual orientation, usually categorized as heterosexual, homosexual, and bisexual, is perhaps the most compelling, yet least understood, component of human sexuality. The contemporary scientifi c paradigm is based upon the assumption that heterosexual orientation is the norm. Thus, deviations from this, particularly homosexual orientation – erotic and emotional attraction to the same gender – have been considered abnormal and have required explanation. Homosexuality has been persistently studied by various disciplines such as biology, psychology, sociology, and anthropology with the goal of fi nding – and presumably eliminating – its cause. The changes in society’s and science’s conceptualization of homosexuality and its ‘treatment’ refl ect the changes in the prevailing paradigms over time of the causes of human behavior. 

For much of the 20th century psychoanalytic theory exerted signifi - cant infl uence on thinking about human behavior. Not surprisingly, until the 1960s, it was commonly believed that homosexuality resulted primarily from pathogenic infl uences in childhood such as an over involved mother and under involved father. The treatment was psychoanalysis, and it was found to be unsuccessful [1]. By the middle of the 20th century a considerable amount of research in human sexuality focused on the role of hormones [2]. Thus, the causes of homosexuality were assumed to be related to hormonal imbalances at different levels of development. Treatment of homosexuality with hormones was as unsuccessful as psychoanalysis [3]. Most recently, there has been a shift to the study of genes and their infl uences on various aspects of the human condition. Gene therapy is already in use for certain medical conditions, but the likelihood for behavioral changes through genetic manipulation remains unknown. 

Nesse [4] writes of ‘Darwinian Medicine’. In this light, he tries to understand why the human body is not better designed and why therefore, diseases exist at all. The genetic/Darwinian paradigm has extended its infl uence to the social sciences, and the infl uence is most clearly seen in the emergence of the new discipline of evolutionary psychology. Evolutionary psychology holds that human behavior can be understood in terms of its adaptive value. Behaviors commonly exhibited by humans can be expected to have contributed to survival and reproduction in the evolutionary past, thus perpetuating the genes that infl uenced the behaviors. In light of the increased visibility and infl uence of the evolutionary paradigm, it seems only natural to extend it to the study of homosexuality. However, it is clear that, historically, homosexuality has not been amenable to explanation by a single model. This is undoubtedlydue to the complexity of the factors infl uencing its development. Thus, we are taking a more integrative approach in this paper. We will fi rst present recent theory on the evolution of homosexual behavior and then try to integrate it with research and theory from the fi eld of (neuro-)endocrinology.

Evolution and homosexual behavior 
The study of homosexual behavior has been impeded by a lack of reliability for the term ‘homosexual’ [5, 6]. Furthermore, there is poor construct validity for the concept of sexual orientation [7, 8]. Muehlenhard [9] has pointed out that many categories (e.g., homosexual / heterosexual) used as variables in sexuality research are social constructions lacking in real meaning and thus pose serious methodological problems. Not surprisingly, in view of the serious psychometric problems involved, all psychological theories of sexual orientation development are lacking in empirical support [10]. The fi rst and most widely recognized evolutionary theory of homosexuality is that of E. O. Wilson [11, 12] and is based on the concept of kin-selection (i.e., a sociobiological explanation for the evolution of altruistic behaviors). 

This theory holds that during the course of human evolution homosexual individuals may have helped family members, through direct or indirect provision of resources, to reproduce more successfully than they would have otherwise. Thus, genes for homosexual behavior would have been propagated indirectly through relatives. The theory has been criticized for a variety of reasons including reliance on a number of false assumptions [13, 14] and a lack of supporting evidence [15, 16, 17, 18]. Consequently, it has been rejected as an explanatory model [6]. The general consensus of writers in the fi eld of evolutionary psychology has been that homosexual behavior in humans does not have adaptive value. 

Some authors consider homosexual behavior to be biologically maladaptive because, they argue, it has no association with potential reproductive success [19, 20, 21, 22]. In most cases, it has been considered best explained as a by-product of the plasticity of the human brain and the resultant variability of human sexuality [16, 18, 23, 24]. Miller [25] has suggested that male homosexuality is a by-product of variable brain feminization associated with personality traits (e.g., empathy) that make males attractive to females and better fathers. In this theory, sexual orientation is conceptualized as a polygenetic trait, i.e. it is infl uenced by a number of genes. Some of these genes might shift male brain development, and thus behavior, into the female direction. Although some feminization contributes to male reproductive success, too much would have deleterious effects. 

Due to normal genetic variation, a small percentage of men would be over-feminized and thus, show more feminine brains, behavior, and perhaps even bodies [25]. However, there is no scientifi c evidence supporting this speculated linear association between brain development, behavior, and morphology in homosexual men. Recently, a new evolutionary perspective on homosexual behavior has begun to emerge. Ross and Wells [26] have argued that evolutionary explanations of homosexuality have been based upon homosexual expression in contemporary Western societies. They state that these environments do not refl ect the ancestral environments in which the behavior would have evolved nor do they contain the same ecological conditions, which would have affected their expression. Further, Ross and Wells [26] propose that homosexual behavior is an ‘exaptation’ of homosocial behavior. An exaptation is not a direct product of natural selection but a neutral variation of a behavior, which with time demonstrates some fi tness enhancing quality. 

As a result, natural selection acts upon it. According to Ross and Wells [26], male homosocial behavior could have contributed to male survival through increased social support and access to resources. Homosexual behavior would have reinforced homosocial bonds and thus would have been acted upon by natural selection. Vasey [27] has also proposed that some aspects of homosexual behavior in primates may have developed as an exaptation. Further, it has been argued that male homosociality is conducive to increased homosexual behavior [28]. Kirkpatrick [5] and Muscarella [29] argue that the evolutionary study of the topic should be behavior based, focusing on homosexual behavior and not on the unreliable concept of homosexuality. They review much cross-cultural and historical evidence and argue that for most of our species, and for most of our history, bisexual behavior was the norm. 

They also argue that most homosexual behavior has been exhibited by people who do not considered themselves homosexual. This evolutionary perspective on homosexual behavior posits adaptive value for the behavior itself in humans. Kirkpatrick and Muscarella speculate that during the course of human evolution homosexual behavior may have reinforced same-sex alliances, which contributed directly to survival [5, 6, 29] and indirectly to reproduction [29]. Kirkpatrick [5] argues that homosexual behavior comes from individual selection for reciprocal altruism, which would have contributed to resource exchange and a reduction in inter-male aggression. In a similar vein, Muscarella [29] argues that adolescent and young adult hominids were probably socially peripheralized and that the capacity to engage in homosexual behaviorreinforced alliances, which contributed directly to survival. Further, the alliances benefi ted the unique reproductive needs of each sex. 

Same-sex allies helped males climb the social hierarchy more effectively, giving access to females and reproductive opportunities. Same-sex allies amongst females helped them move to the safer and resource richer center of the group, which increased their chances of rahttp://www.51due.com/writing/essay/ising their offspring successfully. The theories put forth by Kirkpatrick [5] and Muscarella [5, 29] do not address sexual orientation per se. Rather, they address the selection of a behavioral response. It is assumed that this has a genetic basis, which varies among individuals such that some would have a much greater disposition than others. The ranges of dispositions to engage in the behavior would interact with a range of personal experiences, ecological conditions, and psychological processes resulting in a general sexual orientation.（essay代写)

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