Oh dear, I see far too many simple statements of personal belief and no discussion. Allow me to reiterate to the only scientific conclusion I've ever seen reached on the subject. Perhaps that will stimulate conversation.
First of all, contary to the mission statements of countless non-profits and internet rants originating from proponents of either side, there is no firm biochemical data on homosexuality (though it has been explored extensively from a psychological perspective, this has appeared to change based on political avant garde of the period the research appeared it - for instance, Freud and Astor held negative veiws of homosexuality, while modern psychology attempts to be more inclusive. Due to those reasons, psychology tends to provide conflicting answers as to homosexuality and cannot be used to examine it at this time), notably due to the fact that any research into the subject is discouraged, as any conclusion able to be derived would most likely anger one side or the other. Thus, we will fall back on paleovirology, and its implications in evolutionary sociology, to attempt to ascertain a scientific perspective.
First, some background. The human genome is filled with endogenus retroviruses - bits and pieces of viral DNA permanently incorperated into the human genome from pandemics in the distant past. Some are more complete than others, and much can be ascertained from the more complete genomes, including how the infection spread and how dangerous it was. Using this method, several teams recently discovered that prehistoric humanity was plagued with a series of highly virulent and mortal STDs - around the level of Typhus or Cholera as far as mortality. In response, a new theory has arisen - one claiming that these STDs were such a selective pressure that they triggered the rise of the sexually restrictive social orders seen in every human culture on Earth. For a deeper explaination of how endogenus retroviruses work, and how we are able to use them, I'd recommend this article for the layman:
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1187282/.
The idea is that, faced with with a pandemic of STDs, each of which was effectivity a death warrant, prehistoric humans put their recently acquired brains to use and created a method to counter the spread - the social order. They had to create a way to both maximize reproduction while at the same minimizing oppurtunities for STDs to spread - but how do you reproduce as much as possible while abstaining from sex? Their answer, universal to all human societies seen today, is really quite ingenius in retrospect. The concept of marriage was developed - though at the time, this was most likely only an understanding within a single group and entailed little more then sexual monogamy. In order to enforce the new practice, humans used social pressure against those who did not conform. Groups of humans which remained entirely promiscuous continued to be ravaged by unchecked STDs, and thus were unable to compete with their neighbors and died out. Therefore, this new order spread rapidly, its benefits quite astounding. And the same time, the proto-order realized the beginning of gender inequalities. The proto-societies required a way to exert social pressure if the new order was to succeed. Females became the target of this, as it was essentially impossible to know if a male was having sex, wheras a pregnant female is easy to discern. Thus, females were highly pressured to not have sex outside of their monogamic relationships, in turn preventing males from having sex and bringing the once rampant promiscuality to a halt.
As hunter-gather societies transitioned into proto-farming cultures, gender inequality became what it has been for all of recording history, with one sex dominating the other. This is because new, stable societies featured much more defined order, and so old rules of survival, no longer need, were repurposed. For instance, in the millions of years of hunter-gathering, human females had evolved to devote less resources to musculature and similar implements, as these were rarely used due to the realities of existence at this point. With an average lifespan of 25 years, humans had a limited reproductive window, but also had a high death rate. As a result, females essentially became pregnant as much as possible in order to maximize offspring. As pregnancy requires extensive resources and limits the woman's abilities at the same time, mature women were generally confined to gathering herbs while mature males hunted game - in turn leading to increased physical attributes in males to represent this (note - this didn't automaticly entail any gender inequality insofar as social groups. Humans remained in relatively small groups and found their time mostly consumed by survival - thus the social stratification, need for extensive order, and other prerequisites of gender inequalities never occured at this point). Now, however, in the new farming communities, the former "provide and protect" mentality of males was vistigial. A pregnant women had previously been very vulnerable, but now, due to increased community size and the rise of architecture, predators were effectively removed. Thus, that mentality was repurposed to create a new social hierarchy, one arguably needed for a large, sedimentry group. The "provide and protect" mentality was now enforced not by any realistic need, but rather by physical differnces between the sexes (themselves no longer needed, as farming was not physically intensive compared to hunting with blunt spears). While patriarchies were more common because of physique, matriarchies occasionally occured when the new order was mixed with fertility myths. Add in various cultural quirks which came about since the past large scale human migration, and you have the universal social order of recorded history.
Now, how does this pertain to homosexuality? For early human groups attempting to enforce the new social order by social pressure, homosexuality was a double-edged sword: it has no inherent element to be shamed (i.e., the pregnant woman), as it is hard to tell if male has had sex, while at the same time, due to the nature of homosexual relations, it spreads virulent STDs at an increased rate (this can be seen in the disproportionate rate of HIV/AIDS infection among homosexuals today). It was also a rising problem - with males increasingly unable to find female partners, many may have turned to homosexuality, as there was no social stigma against it at the time. However, since homosexual relations are not essential to the species like heterosexual reproduction, the new order was able to combat it by placing stigma on homosexuality itself - as opposed to merely prosmiscuality, as seen with the rise of sexual monogamy - thus able to take further steps to prevent homosexual relations by making homosexuality itself a stigma. Due to its increased virulence, groups were likely eager to remove it as completely as possible, and thus left no accomadations for the early equavalent of marriage for homosexuals.
If this theory is correct, the radical idea of a social order worked, and quite impressively - the last of "super STDs" appears to have disappeared from the human species around 10,000 years ago.
In conclusion, the question we are left with is now "Is this still needed?" Due to the extinction of the deadly STDs that once accomadated the rise of gender inequalities (note - gender inequalities were made far worse then was ever required during the rise of "civilization," generally after the invention of writing) and homosexual stigma, the answer is no.
In the spirit of objectivity, I must remind everyone that this social theory makes a key assumption - that the recently discovered STDs, confirmed by genetic sequencing to be
deadly enough, were actually
rampant enough to have been the main factor in the rise of modern group behaviour. Also, keep in mind that the only scientific data which could be interpreted free of speculation would be the discovery of the biochemical reasons for sexual orientation - a field greatly hindered by both sides of the political debate, as each fears a negative result for their side.
As far as I know, this is the only scientificly valid theory that gives a conclusive answer to the debate on homosexuality. As I've told you, it is entirely a sociological cause and effect hypothesis, made possible by the discovery of the previously unheard of mortality of certain prehistoric STDs. On a scientific scale, its not much.
Nevertheless, I hope it gives everyone a deeper insight into the possible evolution and nature of the social structure, and thus allows you all to form arguments with that in mind when considering topics like this.
Remember, Pathos < Ethos <
LOGOS!