This study, which also used brain tissue from autopsies, did not reveal any significant difference between the size of the INAH3 in gay men and straight men. It did, however, show that in gay men, neurons in the INAH3 are packed more closely together than in straight men. PET and MRI studies performed in have shown that the two halves of the brain are more symmetrical in homosexual men and heterosexual women than in heterosexual men and homosexual women.
These studies have also revealed that connections in the amygdalas of gay men resemble those of straight women; in gay women, connections in the amygdala resemble those of straight men. The amygdala has many receptors for sex hormones and is associated with the processing of emotions.
Some studies have shown that the corpus callosum — the main connection between the two halves of the brain- has a different structure in gay men than in straight men. However, other studies have found no difference.
Gay women and gay men are more likely to be left-handed or ambidextrous than straight women and straight men, according to a number of different studies. Some researchers have suggested that this difference in handedness — preference for one hand over the other can be observed in fetuses - is related to differences in the corpus callosum.
However, according to a study that was performed ten years later, the size of the anterior commissure is not affected by sexual orientation. We know from studying rats that exposure to sex hormones in the womb during a critical period in brain development affects future sexual orientation.
By manipulating hormone levels during this time, scientists can make rats engage in homosexual behavior later on. A large amount of brain development takes place during childhood, when you are learning many new things — including how your family and the adults around you believe you should feel about things and what they believe is acceptable behavior.
The education you receive as a child strongly affects how your brain will develop as you grow. For example, children who are given musical training experience changes to areas of the brain associated with hearing and motor control.
Both London taxi drivers and professional piano tuners show increases in gray matter in areas of the brain associated with the skills needed for their professions. The size of the increase in gray matter correlates with the numbers of years of experience. In one experiment, elderly subjects showed increases in gray matter in certain parts of their brains after they were taught to juggle.
With proper rehabilitation, people who have suffered brain damage from strokes can develop new neural connections and regain some of their old skills. However, women do experience changes to the structure of the hypothalamus — which is thought to be associated with sexual orientation - throughout the menstrual cycle.
While changes in hormone levels in the womb during a very specific time can have an effect on future sexual preference, hormone levels have no effect on sexual preference afterwards. Gay men and straight men have the same levels of sex hormones; sex hormone levels are the same in gay women and straight women. Today, however, we know much more about the brain than we did when homosexuality was considered a disease that required treatment, and the amount of knowledge that we have about the brain is increasing.
Perhaps one day we will be able to adjust sexual preference via surgery - focusing on the particular regions of the brain that are associated with sexual preference — or via neural implants or training.
Even if gay people can never stop being attracted to members of the same sex, they can learn not to act on their desires. People already learn to stop smoking, to give up certain foods, and not cheat on their husbands or wives. If they could, should they change their brains or have their brains changed in order to make themselves straight?
I believe that people have the right to engage in any behavior that they choose, as long as their actions do not harm others, and I believe that gay sex and gay relationships do not cause harm to anyone. Therefore, people who are gay by choice have the right to remain that way. Of course, there are abusive and unhealthy gay relationships that should not be tolerated, just as there are unhealthy heterosexual relationships that should not be tolerated.
There is an element of homophobia in that argument— the implication that gay people would become straight, if only they could. Supporting gay marriage becomes equivalent to supporting the construction of wheelchair ramps.
In a blog post for Slate , J. In fact, when we you do so, you reinforce the belief that your behavior is undesirable. Nobody has to prove that biology forces them to vote for a particular political party, practice a certain religion or follow a particular diet. Scientific beliefs change as we gain new information, and sometimes science tells us things that we would rather not hear. Bailey, J. A genetic study of male sexual orientation.
Archives of General Psychiatry , 48 12 : — Balthazart, J. Brain development and sexual orientation. Baroncini, M. Sex steroid hormones-related structural plasticity in the human hypothalamus , NeuroImage , 50 2 : Boyke, J. Training induced brain structure changes in the elderly. By analyzing the DNA of nearly half a million people from the U. Numerous studies have established that sex is not just male or female. Nonetheless, misconceptions persist that same-sex attraction is a choice that warrants condemnation or conversion , and leads to discrimination and persecution.
I am a molecular biologist and am interested in this new study as it further illuminates the genetic contribution to human behavior. The new finding is consistent with multiple earlier studies of twins that indicated same-sex attraction is a heritable trait. As the ease and affordability of genome sequencing increased, additional gene candidates have emerged with potential links to homosexual behavior.
So-called genome-wide association studies identified a gene called SLITRK6 , which is active in a brain region called the diencephalon that differs in size between people who are homosexual or heterosexual.
Genetic studies in mice have uncovered additional gene candidates that could influence sexual preference. A study linked sexual preference to a gene called fucose mutarotase.
When the gene was deleted in female mice, they were attracted to female odors and preferred to mount females rather than males. Science , eaat PubMed Article Google Scholar. Download references. Article 10 NOV News 05 NOV News 04 NOV Research Highlight 03 NOV News 09 SEP Article 03 NOV Francis Crick Institute. Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.
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