Digressing as usual

So we are still trying to find out the real causes of what it means for one sex to desire another of the same sex.
As a human race we breed, subconsciously passing on knowledge to the next generation and so forth to advance in this world. We have certain instincts, like that of a tiny bacteria we essentially yearn for certain things for survival, reproduction being one of them. Although now, rather than being a tiny bacteria, it is way more complex, food, water, shelter, other people, knowledge and such we still strive for. But what if, we eliminated one of these?
What if, that is, there was no sense of future in our neural workings... Rather nothing to continue on out, where sex is carried out for more a pleasure or stress relieving task than to reproduce.
I was just thinking, in Japanese history it was told during the "heian period" (maybe i'll try add a link here), also known as the 'peace era' way back somewhere around 800 years ago. In this period it was known that there were a lot of homosexual relationships. Is it harmony, that lack of urgency that gives us too much freedom to follow our 'natural order,' i.e gaining weight being a problem for the masses in the past, has been shifted to losing weight and trying to get fit in the present.
Perhaps it is a shift in the human psyche that is necessary for the future beings. Perhaps it is a hindrance, or a sign of something wrong; which is why so many people are against it naturally beyond rationality.
I remember learning that in ancient greece it was custom that a younger boy would be paired up with an older man in the military, the older being the mentor and the younger being the pupil, and the younger had to submit to any sexual desire the older would ask of him. It was considered a bonding for the military, a sense of belonging and more reason to fight, apparently.

Some of these arguments would sound completely ridiculous to some, and unfortunately i can't see how, which is why i want you to reply to this theory, and annotate it if you can to help build a better thought.

I think too much, this is a social network so i may as well take advantage of your minds too to help unload some pressure haha.