The relationship between biology and sexual orientation is a subject of research. While scientists do not know the exact cause of sexual orientationthey theorize that Research supports the theory that homosexuality combination of genetic, hormonal, and
Research supports the theory that homosexuality factors determine it. Biological theories for explaining the causes of sexual orientation are favored by scientists  and involve a complex interplay of genetic factors, the early uterine environment and brain structure.
A number of twin studies have attempted to compare the relative importance of genetics and environment in the determination of sexual orientation. Self reported zygositysexual attraction, fantasy and behaviours were assessed by questionnaire and zygosity was serologically checked when in doubt.
Other researchers support biological causes Research supports the theory that homosexuality both men and women's sexual orientation.
A study of all adult twins in Sweden more than 7, twins  found that same-sex behavior was explained by both heritable factors and individual-specific environmental sources such as prenatal environment, experience with illness and trauma, as well as peer groups, and sexual experienceswhile influences of shared-environment variables such as familial environment and social attitudes had a weaker, but significant effect.
Women showed a statistically non-significant trend to weaker influence of hereditary effects, while men showed no effect of shared environmental effects. The use of all adult twins in Sweden was designed to address the criticism of volunteer studies, in which a potential bias towards participation by gay twins may influence the results.
Biometric modeling revealed that, in men, genetic effects explained. Corresponding estimates among women were. Although wide confidence intervals suggest cautious interpretation, the results are consistent with moderate, primarily genetic, familial effects, and moderate to large effects of the nonshared environment social and biological same-sex sexual behavior.
Twin studies have received a number of criticisms including self-selection bias where homosexuals with gay siblings are more likely to volunteer for studies. Nonetheless, it is possible to conclude that, given the difference in sexuality in so many sets of identical twins, sexual orientation cannot be attributed solely to genetic Another issue is the recent Research supports the theory that homosexuality that even monozygotic twins can be different and there is
Research supports the theory that homosexuality mechanism which might account for monozygotic twins being discordant for homosexuality.
Gringas and Chen describe a number of mechanisms which can lead to differences between monozygotic twinsthe most relevant here being chorionicity and amniocity. Monoamniotic twins share a hormonal environment, but can from
Research supports the theory that homosexuality 'twin to twin transfusion syndrome' in which one is "relatively stuffed with blood and the other exsanguinated".
Chromosome linkage studies of Research supports the theory that homosexuality orientation have indicated the presence of multiple contributing genetic factors throughout the genome. In Dean Hamer and colleagues published findings from a linkage analysis of a sample of 76 gay brothers and their
Research supports the theory that homosexuality. Gay brothers who showed this maternal pedigree were then tested for Research supports the theory that homosexuality chromosome linkage, using
Research supports the theory that homosexuality markers on the X chromosome to test for similar alleles.
This was popularly dubbed the " gay gene " in the media, causing significant controversy. A later analysis by Hu et al. In the full sample they did not find linkage to Xq Results from the first large, comprehensive multi-center genetic linkage study of male sexual orientation were reported by an independent group of researchers at the American Society of Human Genetics in Significant linkage was also detected in the pericentromeric region of chromosome 8, overlapping with one of the regions detected in the Hamer lab's previous genomewide study.
The authors concluded that "our findings, taken in context with previous work, suggest that genetic variation in each of these regions contributes to development of the important psychological trait of male sexual orientation". Female sexual orientation does not seem to be linked to Xq28,   though it does appear moderately heritable. In addition to sex chromosomal contribution, a potential autosomal genetic contribution to the development of homosexual orientation has also been suggested.
In a study population composed of more than participants, Ellis et al. They also found that "unusually high" proportions of homosexual males and homosexual females were Rh negative in comparison to heterosexuals. As both blood type and Rh factor are genetically inherited traits controlled by alleles located on 9 and chromosome 1 respectively, the study indicates a potential link between genes on autosomes and homosexuality.
The biology of sexual orientation has been studied in detail in several animal model systems. In the common fruit fly Drosophila melanogasterthe complete pathway of sexual differentiation of the brain and the behaviors it controls is well established in both males and females, providing a concise model of biologically controlled courtship.
Without the gene, the mice exhibited masculine sexual behavior and attraction toward urine of other female mice.
Those mice who retained the gene fucose mutarotase FucM were attracted to male mice. In interviews to the press, researchers have pointed that the evidence of genetic influences should not be equated with genetic determinism.
According to Dean Research supports the theory that homosexuality and Michael Bailey, genetic aspects are only one of the multiple causes of homosexuality.
InNature published an article with a genome association Research supports the theory that homosexuality on male sexual orientation. The research consisted of
Research supports the theory that homosexuality, homosexual men and 1, heterosexual men. Levay's research suggested that the hypothalamus of gay men is different from straight men. The researchers found another gene, named "thyroid stimulating hormone receptor" TSHR on chromosome 14 which dna sequence is different also for gay men.
The previous research also indicated that grave disease had been seen more in gay men than in straight men. It had been presumed that the overactive TSHR hormone lowered body weight in gay people. A study suggests linkage between a mother's genetic make-up and homosexuality of her sons.
Women have two X chromosomes, one of which is "switched off". The inactivation of the X chromosome occurs randomly throughout the embryo, resulting in cells that are mosaic with respect to which chromosome is active. In some cases though, it appears that this switching Research supports the theory that homosexuality can occur in a non-random fashion.
This maternal immunization hypothesis MIH begins when cells from a male fetus enter the mother's circulation during pregnancy or while giving birth. These Y-linked proteins would not be recognized in Research supports the theory that homosexuality mother's immune system because she is female, causing her to develop antibodies which would travel through the placental barrier into the fetal compartment. Successive male fetuses are then attacked by H-Y antibodies which somehow decrease the ability of H-Y antigens to perform their usual function in brain masculinisation.
However, the maternal immune hypothesis has been criticized because the prevalence of the type of immune attack Research supports the theory that homosexuality is rare compared with the prevalence of homosexuality. Inresearchers discovered a biological mechanism of gay people who tend to have older brothers.
They think Neuroligin 4 Y-linked protein is responsible for a later son being gay.
The result also indicates that number of pregnancies, mothers of gay sons, particularly those with older brothers, had significantly higher anti-NLGN4Y Research supports the theory that homosexuality than did the control samples of women, including mothers of heterosexual sons.
InItalian researchers conducted a study of about 4, people who were the relatives of 98 homosexual and heterosexual men. Female relatives of the homosexual men tended to have more offspring than those of the heterosexual men. Female
Research supports the theory that homosexuality of homosexual men on their mother's side tended to have more offspring than those on the father's side.
The researchers concluded that there was genetic material being passed down on the X chromosome which both promotes fertility in the mother and homosexuality in her male offspring. Research conducted in Sweden  has suggested that gay and straight men respond differently to two odors that are believed to be involved in sexual arousal. The research showed that when both heterosexual women and gay men are exposed to a testosterone derivative found in men's sweat, a region in the hypothalamus is activated.
Heterosexual men, on the other hand, have a similar response to an estrogen-like compound found in women's urine. Researchers have suggested that this possibility could be further explored by studying young subjects to see if similar responses in the hypothalamus are and then correlating these data with adult sexual orientation. A number of sections of the brain have been reported to be sexually dimorphic; that is, they vary between men and women.
There have also been reports of variations in brain structure corresponding to sexual orientation. InDick and Michel A. Hofman reported a difference in the size Research supports the theory that homosexuality the suprachiasmatic nucleus between homosexual and heterosexual men.
Research on the physiologic differences between male and female brains are based on the idea that people have male or Research supports the theory that homosexuality female brain, and this Research supports the theory that homosexuality the behavioral differences between the two sexes.
Some researchers state that solid scientific support for this is lacking. Although consistent differences have been identified, including the size of the brain and of specific brain regions, male and female brains are very similar. Simon LeVaytoo, conducted some of these early researches. This was a relevant area of the brain to study, because of evidence that it played a role in the regulation of sexual behaviour in animalsand because INAH2 and INAH3 had previously been reported to differ in size between men and women.
He obtained brains from 41 deceased hospital patients. The subjects were classified into three groups. The first group comprised 19 gay men who had died of AIDS -related illnesses. The second group comprised 16 men whose sexual orientation was unknown, but whom the researchers presumed to be heterosexual. Six of these men had died of AIDS-related illnesses. The third group was of six women whom the researchers presumed to be heterosexual.
One the women had died of an AIDS-related illness.
The HIV-positive people in the presumably heterosexual patient groups were all identified from medical records as either intravenous drug abusers or recipients of blood transfusions. Two of the men who identified as heterosexual specifically denied ever engaging in a homosexual sex act. The records of the remaining heterosexual subjects contained no information about their sexual orientation; they were assumed to have been primarily or exclusively heterosexual "on the basis of the numerical preponderance of heterosexual men in the population".
Research supports the theory that homosexuality, the INAH3 group appeared to be twice as big in the heterosexual male group as in the gay male group; the difference was highly significant, and remained significant when only the six AIDS patients were included in the heterosexual Research supports the theory that homosexuality. However, other studies have shown that the sexually dimorphic nucleus of the preoptic area, which include the INAH3, are of similar size in homosexual males died of AIDS to heterosexual males, and therefore larger than female.
This clearly contradicts the hypothesis that homosexual males have a female hypothalamus. Furthermore, the SCN of homosexual males is extremely large both the volume and the number of neurons are twice as many as in heterosexual males. These areas Research supports the theory that homosexuality the hypothalamus have not yet been explored in homosexual females nor bisexual males nor females.
Research supports the theory that homosexuality and colleagues attempted to identify the size differences reported in INAH 1—4 by replicating the experiment brain sample from other subjects: The researchers found a significant difference in INAH3 size between heterosexual men Research supports the theory that homosexuality heterosexual women.
The INAH3 size of the homosexual men was apparently smaller than that of the heterosexual men, and larger than that of the heterosexual women, though neither difference quite reached statistical significance. The results for INAH3 weight were similar to those for INAH3 size; that is, the INAH3 weight for the heterosexual male brains was significantly larger than for the heterosexual female brains, while the results for the gay male group were between those of the other two groups but not quite significantly different from either.
The neuron count also found a male-female difference in INAH3, but found no trend Research supports the theory that homosexuality to sexual orientation. A study, Garcia-Falgueras and Swaab asserted that "the fetal brain develops during the intrauterine period in the male direction through a direct action of testosterone on the developing nerve cells, or in the direction through the absence of this hormone surge.
In this way, our gender identity the conviction of belonging to the male or female gender and sexual orientation are programmed or organized into our brain structures when we are still in the womb. There is no indication that social environment after birth has an effect on gender identity or sexual orientation.
Research supports the theory that homosexuality In many species, a prominent feature of sexual differentiation is the presence of a sexually dimorphic nucleus SDN in the preoptic hypothalamus, which is larger in males than Research supports Research supports the theory that homosexuality theory that homosexuality females.
Neurons of the oSDN show aromatase expression which is also smaller in male-oriented rams versus female-oriented rams, suggesting that sexual orientation is neurologically hard-wired and may be influenced by hormones. However, results failed to associate the role of neural aromatase in the sexual differentiation of brain and behavior in the sheep, due to the lack of defeminization of adult sexual partner preference or oSDN volume as a result of aromatase activity in the brain of the fetuses during the critical period.
Having said this, it is more likely that oSDN
Research supports the theory that homosexuality and Research supports the theory that homosexuality may be programmed through an androgen receptor that does not involve aromatisation. Most of the data suggests that homosexual rams, like female-oriented rams, are masculinized and defeminized with respect to mounting, receptivity, and gonadotrophin secretion, but are not defeminized for sexual partner preferences, also suggesting that such behaviors may be programmed differently.
Lawrence Mayer and Dr. But, as Mayer and McHugh, a leading psychiatrist, make clear, the science is far from settled. The authors reviewed the findings of hundreds of peer-reviewed studies on gender and sexuality, and their conclusions challenge some of the popular cultural myths that surround questions of sexual orientation and gender identity. They argue that science is not settled when it comes to understanding the origins of sexual attraction, sexual desires and sexual behaviors. In addition, by presuming that sexual orientation is rooted in genetics, researchers or clinicians may miss other relevant factors — including, for example, childhood physical or sexual abuse, which is experienced in disproportionately high numbers by nonheterosexuals.
Social stress from stigma and discrimination is the root cause of the poor mental health of persons identifying as gay, lesbian, bisexual or transgender. Removing social stress, by normalizing nonheterosexual behaviors, will resolve these issues.
The report identifies several shortcomings of the social stress model: The new report strongly counters this transgender myth. Early transitioning, using medical treatments like puberty blockers, is the best way to treat transgender children.
They are increasingly receiving therapies that affirm their felt genders and even hormone treatments or surgical modifications at young ages.
The relationship between biology and sexual orientation is a subject of research. While scientists do not see the exact cause of sexual orientation , they theorize that a colloid of genetic, hormonal, and social factors determine it.
Biological theories for explaining the causes of sex orientation are favored past scientists  and betoken a complex interplay of genetic factors, the prehistoric uterine environment and intellect structure. A number of twin studies have attempted to compare the comparable importance of genetics and environment in the doggedness of sexual orientation.
Self reported zygosity , earthy attraction, fantasy and behaviours were assessed by questionnaire and zygosity was serologically checked when in incredulity.
Other researchers support biological causes for both men and women's sexual familiarization. A study of all adult twins in Sweden more than 7, twins  found that same-sex behavior was explained by way of both heritable factors and individual-specific environmental sources such as prenatal environment, know-how with illness and trauma, as well as peep through groups, and sexual experiences , while influences of shared-environment variables such as familial environment and group attitudes had a weaker, but significant effect.
I n a recent Guardian article , Simon Copland argued that it is very unlikely people are born gay or presumably any other sexual orientation. Scientific evidence says otherwise. It points strongly to a biological origin for our sexualities. I would argue that understanding our fundamental biological nature should make us more vigorous in promoting LGB rights. Three gene finding studies showed that gay brothers share genetic markers on the X chromosome; the most recent study also found shared markers on chromosome 8.
This latest research overcomes the problems of three prior studies which did not find the same results. Gene finding efforts have issues, as Copland argues, but these are technical and not catastrophic errors in the science. But each of these genes has a small effect on the trait so do not reach traditional levels of statistical significance.
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In a review of 58 newsletters published between and , that article synthesizes the recent have of social research on older lesbian, gay male, and androgyne adults in order to summarize existing knowledge about these formations, to guide future research on aging, and to identify the substantive issues affecting their lives. Based on a life-course where one is coming from, the primary research domains identified include the interplay of lives and historical times and linked and interdependent lives.
After reviewing the literature in each of these areas, the article presents an examination of the strengths and limitations of the substance of knowledge and an thumbnail sketch of a blueprint for prospective research. As the global folk is aging dramatically, the figure up of older lesbian, gay, and bisexual LGB adults is apposite increasing substantially. Given the ambiguities of defining sexual orientation, 1 the reluctance of individuals to openly self-identify, and the underage of population-based studies incorporating measures of sexual orientation, it has been difficult to estimate the proportion of the older of age population that is LGB.
Largest research and probability-based surveys incorporating measures of sexual orientation and sexual behavior of the U. In large urban centers, estimates of the number of LGB persons increase substantially, with women reporting between 2.
What's my ex thinking right now?Homosexuality can refer to both attraction or sexual behavior between people of the same Continuum Theory of Sexual Orientation Disputed by Researchers. Three gene finding studies showed that gay brothers share genetic markers by raising him as a girl makes any social theory of sexuality very weak. People worry that scientific research will lead to “cures” for homosexuality (which is an odd With your support, we can continue bringing The Guardian's..
Biology and sexual orientation
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- Most of the theories relate to research on male homosexuality. The evolution of lesbianism is relatively understudied...
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- Report refutes LGBT 'born that way' theory Study from researchers at report, scientific evidence fails to support the “born that way” theory of. The relationship between biology and sexual orientation is a subject of research. Biological theories for explaining the causes of sexual orientation are favored by of a heterosexual, homosexual, bisexual, or asexual orientation, include genes, Other researchers support biological causes for both men and women's .
- Aging and Sexual Orientation: A Year Review of the Literature
- Epigenetic theories of homosexuality - Wikipedia
- Biology and sexual orientation - Wikipedia
- Epigenetic theories of homosexuality concern the studies of changes in gene expression or This research gives support to the hypothesis that homosexuality stems from the under expression of certain genes on the DNA sequence involved .
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