Interesting Article

Thinking about Gay Male Brains.
Todd Murphy, 1999
There is one brain part, called the anterior commisure, that's bigger in gay men's brains than in those of heterosexual males. Most of my thoughts here are about looking at what that might mean, and how it might appear. ( Reference)
So, what's it do?
It connects two structures together. The amygdala on each side of the brain.
So, what does the amygdala do?
Its a very, very emotional structure. And it's fast. If you suddenly notice a bus heading toward you, and you feel a 'burst' of fear, that's your amygdala; the one on the right. If you feel a burst of elation when someone looks at you with attraction in their eyes, that's your amygdala, too; the one on the left.
A gay man's brain has more connections between the opposite emotional centers than other brains.
The amygdala does an important kind of recognition, too. It recognizes other people, or more importantly, how they're feeling. It responds to facial expressions, tones of voice, and, I'd guess, body language as well.
My guess is that its important in seeing potential mates, and so, its the part that knows who you're attracted to, gay, straight, transsexual, bisexual or whatever.
The gay male brain uses the same parts to be attracted to a man that I use to be attracted to a woman.
I cannot help but wonder if the extra connections might allow extra recognition skills, and a wider sense of what a person's meaning might be. When a male brain selects people of the same gender as the focus for sexual feelings, it gives its owner a set of concerns and needs in common with women. Men become the people they want to be with, forcing them to pay attention to men's needs, and women become the object of identification, at least in some ways. At the same time they ARE men, so they still have to identify there, too. As a straight man, an attractive woman 'means' something very different to me than she does to a gay man. And guess what? The amygdala mediates our experience of 'meaningfulness'.
Such a person would be able to empathize with a very large portion of the total population; larger than heterosexuals of either gender.
Most evolutionary biologists will agree that if a species preserves a trait, its because that trait helps that species survive, or at least did so when it first emerged.
One of the traits of the human species is that close 10 percent (the number changes according to who does the counting) of our populations are gay. If Darwin (and some others) are right, the our species needed gay males when we first appeared, and we might need them now.
What for?
Well, gay men do not compete with straight men for one thing, but they understand many, if not most, uniquely male concerns, because they are men.
And they share enough in common with women that they understand women's concerns, too. Many lesbians are a bit taken aback by how indifferent many gay men are to feminist political concerns, but those aren't the women's concerns I mean. I'm talking about such things as 'cognitive style', 'linguistic patterns' and other things that you need a special dictionary to get.
Gay males might have enhanced their tribe's ability to respond to danger quickly. Their voice in the councils of the first human tribes could have been a profound advantage.
There are two things that help an individual be heard in human cultures. One is to be the boss, and the other is to have as few conflicts with others as possible.
Gay males, being less interested in war than other males, do not conflict with their tribal neighbors.
They do not compete with straight males for sexual opportunities,
And, they do not compete with women over the resources for their young. A hundred thousand years ago, this was probably VERY important. It takes a decade to raise a child, at least. In a ten-year period, most of our young probably had to live through at least one lean season. When it was going on, the gay man only had to find food for one. But he was quite strong and intelligent to find food for several, just like anyone else, if it was to be had at all.
Our species arose 100,000 years ago, and we were hunters and gatherers. Most of these societies today are a loose kind of democracy, and the chiefs don't really have the power to command obedience from anybody. Decisions were and are made in councils. In our earliest history, these decisions were sometimes a matter of life and death. Making sure that our populations produced some individuals who had extra empathetic skills might have given us more intelligent leadership than otherwise. The larger anterior commisure implies that gay males might be more able to perceive meaningfulness, too. "Meaningfulness" is an amygdaloid function - innocuous things become omens, possibly selected because the event taken as the omen has some association with a concern among one's people. (Stimulate your amygdala - learn more here)
One example might be what a storm cloud means when its windy outside. The extra left/right connectivity in gay males would give them a greater sense of the nuances and subtle implications of events in their world. Being men, however, they would have a greater ability to articulate their subtler perceptions, because the male brain is more 'single-tasking' than the female brain; it is more likely to use one or two areas at a time - including the language centers.
Because gay males have more communication between the hemispheres, they percieve non-verbal information (including the sort we call intuitive) more readily then straight males. Because they still possess male brains, their cognitive processes are more focused (less multitasking) than they would be in women, allowing them an advantage in getting non-verbal information into words, where it can be shared with others. An intuition becomes a channeled voice. A dream contains spoken instructions. A gay male, all other conditions being equal, was more able to go from a sense-that-something-is-wrong to seeing and describing a specific danger. They might also be better able to find ways to improve things, be more comfortable, and stay healthy.
Consider the stereotype that gay men are 'esthete' - they are gourmets when eating, film critics when seeing movies, interior designers at home, and fashion and grooming experts in front of mirrors. Nothing but the best. Now, imagine that same trait 100,000 years ago, and add to it the caveat that people acted for their tribe as much as for themselves, there being little one could claim as one's own. Nothing but the best and most sheltered campsite. Nothing but the clearest water. Everyone should be clean and attrective (by whatever standard his nation held) - as much as possible. With their extra emotional sensitivity, they would encourage people to be nice to one another. Further, freedom from many of the usual social obligations - like the need to let others save face - could allow gay males to be more vocal than other males might be. Someone demanding the best for himself in those days would have had to demand the best for the whole tribe.
I know I'm making many generalizations here, and many gay men do not fit the stereotype, but my point is that gay male traits, though held by only a few, can benefit many.
When a gay male had an opinion, a hundred thousand years ago, his people probably listened.
In our earliest evolutionary history, as hunter/gatherers, we were better able to survive our crises, and to avoid them when we could, by having a group with a different set of cognitive skills who tended to avoid the conflicts that were most pressing to everybody else. They probably were important peacemakers in our first cultures. And peace is one thing that we need to survive, and to raise our young.
One study found that women who were pregnant in Berlin at the end of World War Two delivered a slightly higher percentage of gay male children than others. Perhaps the response to war is to try and deliver more peacemakers.
That may be why our gene pool contains instructions for making our populations include 10 percent gay males.
So why should this man, and not that man, be gay?
There is a process that could create this difference. The emergence of a recessive, neotanous trait.
Neotany is the name used when an adult in a species retains a childhood trait. The best-know example is human curiosity. Other primate species are as curious as our children, but it stops with puberty. Our adults are capable of retaining the trait their whole lives.
Brains don't grow uniformly. They grow in steps. First one part grows outstrips the others, then another gets bigger. Then another. Then another.
My guess (speculation) is that there is a phase in the growth of every male brain when the anterior commisure has outstripped its neighboring structures. I also guess that there is a trigger that signals when its time for the anterior commisure to stop growing.
And that, in gay males, this trigger is absent. This kind of adaptation is called "Neoteny"
Some gay men say that they've 'always known' they were gay. Others have said that there was a single decisive sexual experience that brought it out.
Its possible that the anterior commisure has two growth spurts when it might be able to shed its 'stop growing' trigger. One during in the womb, and another after birth, but before puberty. Perhaps there are several such 'windows of opportunity' in the development of a man's brain. There isn't enough evidence at this point to prove or disprove the case. The simplest thing I can imagine is an environmental 'cue' of some sort, either in the womb or in the environment.
One more thing about the anterior commisure. Its in the limbic system, and the limbic system is now the strongest contender as the source, within the brain, of religious and mystic experiences. There are scores of studies to support this, most of them published in medical journals, and are still unknown in spiritual teachings.
Nevertheless, a conclusion appears: Gay men were probably our first spiritual leaders. Our Shamans. In that social position, they would have been free to expect that their words would be heard, they would have been able to exploit their cognitive skills to the maximum, and they would have been able to access many altered states of consciousness that would've been unavailable to others.
The trust and respect that a skilled gay shaman might have been able to command might allow him to induce the placebo effect in other during times of illness, too.
Gay men may once have healed their people, led them spirituality, soothed interpersonal conflicts, and help them anticipate and avoid threats to their survival.
Who knows? Perhaps gay male sexual preference is a by-product of a specific group of cognitive and emotional skills that helped us survive - skills that may be expensive for the individual gay man, but were essential for the population as a whole.
A 100 percent heterosexual population might have gone extinct.
But then, we don't have a 100 percent straight population, do we?

Allen & Gorski, "Sexual Orientation and the size of the Anterior Commisure in the Human Brain"
Proceedings of the National Academy of Sciences, Vol. 89, 7199-7202, August 1992"