Genetic Research
Features genetics homosexuals have been studied little. Scientists are searching for the gene or genes of homosexuality since the 1980s. As in many other studies, trying to distinguish the symptoms of congenital acquired an important material has been obtained from the analysis and relatives, especially identical twins. It has been shown frequent presence of homosexual men several older brothers, and of manifestations of homosexuality in both identical twins, even in cases where they were brought up separately.
According to the research, if identical twins homosexual men, the chances are that he will be inclined to homosexuality, is 52%; dizygotic twins if, the probability is 22%. Similar results were obtained with regard to women: the probability that a woman will become a lesbian, as her monozygotic sister is 48%; if women are dizygotic twins, the probability is 16%. The higher the identity of the genetic material, the greater the likelihood that sexual orientation will be the same. This means that the tendency is to homosexual genotype.
Received to date results do not allow unambiguous interpretation of homosexuality as an exclusively genetic characteristic is fixed, but do not allow to abandon further research in this direction. Some features of the genetic material are common in about 20% of the surveyed homosexual men. There is evidence that the variability Xq28 locus in human chromosome X-linked with homosexuality.
In flies, fruit flies show the effect of certain genes on sexual behavior. In particular, males homozygous for the mutant gene fru (fruitless) characteristic of homosexual behavior (they do not care for females, caring only for the males and stimulate other males care for themselves). Fru gene is expressed in certain areas of the brain fly Drosophila. Female, whose gene Les (Lesbian) is mutant, caring for other females. Mutant gene variants Viola and cause sluggish bisexual behavior in male fruit flies.
Hormonal System Research
Several studies have tested the hypothesis about the impact on male sexual orientation levels of androgens. It was assumed that homosexual men are associated with reduced levels of androgens in the blood. This hypothesis is currently represented by researchers unconvincing. Some authors reported that there were differences androgen levels of homosexuals and heterosexuals, but others have found no difference. In addition, studies have shown that the administration of androgens homosexual men do not change their sexual orientation: sexual desire increased in subjects, but it still was directed to the people of their gender.
More convincing is the hypothesis of the researchers prenatal influence on the formation of the sexual orientation of fetal hormone levels in the mother's blood. According to this hypothesis, some neural areas around the hypothalamus undergo differentiation between the 2nd and 5th months of fetal development, and this differentiation depends on the level of sex hormones in the blood. If hormones disrupted the development of this part of the brain will be atypical: male embryo will develop atypically "male" structure in the embryo female - not typical "female". Cause of hormonal levels in the mother's blood can be stressful or different genetic effects. One of the options - an excessive influence of testosterone on female fetuses. Among the possible consequences of this are called "boyish" behavior of girls and the development of homosexual women.
Brain Research
As manifestations of homosexuality and sexuality in general, are controlled by the nervous system, attention to a wide range of brain researchers drawn to this issue. Many neuroscientists have identified differences in brain structure homosexual and heterosexual individuals. Thus, it was found that the region of the posterior hypothalamus responsible for sexual behavior in animals in homosexual men in two times less than in heterosexual, and is close to the volume of the structure of heterosexual women. The reasons for these differences are not yet known. Also, it is not known what role this structure plays in shaping sexual orientation.
Russian psychiatrists have been suggested that there is a dysfunction of homosexuals, close to the clinical picture to a shortage of the right hemisphere. According to surveys conducted, homosexuals observed failure of motor and tactile functions of the left hand, the restriction of the volume of perception and the deterioration of performance of tasks associated with negative emotions. In 1997 he published the results of Russian studies, which revealed that homosexuals worse than heterosexuals perform spatial tasks and tests for aiming, which can also testify about the features of lateralization of cerebral functions such persons, but it remains a mystery what material were made such findings, because until 1993 homosexuality was cause for criminal prosecution in Russia. Other studies conducted in the United States, by contrast, show that homosexuals are superior to heterosexuals in mastering certain academic disciplines.
Evolutionary Concepts
According to Kinsey, A. (1948), there are a number of evolutionary concepts of homosexuality. As part of these concepts tendency to homosexual behavior has a genetic basis and is manifested in different individuals in varying degrees. In general, the adaptive function of same-sex sexual activity is that they reduce the intra-tension, sexual rivalry and competition for livelihood, promote solidarity groups provide strong alliances between men, increasing the likelihood of survival. This process is associated in particular with the biological mechanism of the feminization of the male brain, resulting in reduced properties masculine and feminine increase. Homosexuality is a byproduct of the need to survive in the wild, not only individuals, but also the whole population.
Also, with sufficient population to the fore the quality of care for offspring, and homosexuality appears here as a tool to monitor the evolution of population size. When uncontrolled population growth sooner or later there is a problem of the form of lack of food and places to live. Moreover may be superseded by other species with similar needs, and most importantly - there is a risk of total destruction of species that are food for the first place. Non-reproductive individuals of homosexual behavior is social and altruistic, the survival of the population as a whole. Without offspring production, they are involved in procuring the means of subsistence for his flock, protecting its territory, caring about other babies. According to the concepts of population, there is a real need of homosexual individuals.
References
Kinsey A. C., Pomeroy W. B., Martin C. E. Sexual behavior in the human female. — Philadelphia: Saunders, 1948.
Dittmann R. W., Kappes M. W. E., and Kappes M. H., 1992. Sexual behavior in adolescent and adult females with congenital adrenal hyperplasia. Psychoneuroendocrinology 17:153-70
Bailey J. M., Pillard R. C. 1991. A genetic study of male sexual orientation. Archhives of General Psychatry 48:1089-96
