It has existed, for over 4,500 years as evidenced by art history and archaeological findings, from the beginning of recorded story, both in the animal kingdom and among human beings. Today scientists are looking at genes, brain structure, prenatal environment and hormones and it is quite clear that the primary roots of the trait lie in biology. Sexual orientation is a complex trait which appears to have multiple mechanisms acting upon it. It is unlikely that there is a single cause, they do not expect there to ever be a single master “gay gene”.

Scientific evidence that plays a factor in sexual orientation includes genetic evidence, which is the best evidence that proves that genetics play a significant role. Sexual orientation, as a trait, is similar to being born right or left handed; the genetic Influence on both traits Is estimated at less than 50% and both seem to be established at an early age or before birth. (Blanchard, 1999) The heritability of sexual orientation Is estimated between 30% and 50%. By comparison, the heritability of left- handedness is estimated at 26% or lower. Bailey, 1993) . The first major gene study, studied 110 families of homosexual men, and found increased rates of same sex orientation in relatives on the mothers’ sides of their families, suggesting a link o the X chromosome transmitted by the mother to the fetus (Hammer,1993) The next factor would be hormonal influences. Many parents often fear if their parenting can influence a child’s orientation. Studies find that true only in the womb. Each additional older brother increases the odds of homosexuality in a male by 33%.

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Only biological older brothers predict men’s sexual orientation, which strongly suggest prenatal orally (Bogart, 1996) Some of the first modern-era scientists looking at the Orleans of homosexuality were proposing what they called a “prenatal Ramona theory” the idea that the brains of some fetus do not become sexually differentiated in the way most fetus do, and that the result is a partially masculine brain structure in girls or a partially feminizes brain structure in boys.

They were looking for signs of the gender atypical of prenatal hormones, and believed to find the prenatal hormone androgen. By manipulating the prenatal hormone levels in laboratory sheep and mice has been shown to alter sexual orientation. The levels of androgen received by the fetus are responsible for most hysterical characteristics that differentiate men and women. Evidence shows in many lesbian and bisexual females of brain structures that haven been partially masculine by exposure to high levels of the hormone androgen before birth. Overlook & Cordon, 2000) Another factor would be brain structure and organization. Many traits of brain Tunnels, oral anatomy Ana cognation aurorally Titter Detente ten sexes. Gay men and woman do differ biologically from straight counterparts in significant ways. The first finding of anatomical difference in brain structures was in 1991. The neurologist examined the brains of deceased men, straight and gay. He concentrated on the hypothalamus, which is found in the brains of all mammals.

It is linked to the limit system, which is involved in control of sexual activity and emotions. He found that the frontal section of the hypothalamus contains a small group of cells, was involved in male typical sexual behavior. This group of cells is known as the NINA, it is generally larger in men than in woman. He reported that the NINA was smaller, on average in gay men. They also found that changing the hormone levels in vibratory mice while they are still in the womb causes the hypothalamus to be smaller, and causes males to display courting behavior towards other males.

The same area in sheep is smaller in male rams that mate exclusively with other rams than those rams that mate with ewe’s. (Leave, 1991) Homosexuality has been called “unnatural” by those whose define it as a choice. Ironically, nature itself shows that nothing could be farther from the truth. Aristotle recorded the earliest observation of same sex behavior among animals some 2300 years ago. Hundreds of species, exhibit same sex mating, courtship and sexual behavior. Sometimes it may be for cultural, dominance or Just for pleasure reasons.

Nature is anything but predictable, and there are at least 500 species and perhaps more examples of non traditional pairing in the wild. Can a person’s orientation be changed? Science is firmly on the path of establishing the innate nature of the trait of homosexuality. Evidence leads to conclude that biology, not choice, drives sexual orientation, both gay and straight. However, a tiny minority of therapist still engage in therapy aimed at changing a person’s sexual orientation, by using “reparative or reorientation” therapy.

It has been reported to not be successful. Even though, science has proved that biology not choice, drives sexual orientation, in this world, there are many who cling to mistaken ideas and old notions that comfort them, bring order to the chaos of life, and reassure them, and when these ideas are proven wrong, these people flounder helplessly. Science has never been easy however; as with everything else in this world, there are no specific black or white sides, only shades of grey. REFERENCE’S