In responding to comments a few weeks back on Facebook, I made a statement which I immediately realized could be misunderstood: I could be interpreted as claiming that homosexuality was a genetic disease. That is not what I stated; this article is intended to clarify that.
The argument put forward was in essence a claim that there is a perfectly rational non-religious basis for considering homosexuality dysfunctional, based entirely on basic principles of evolution. I do not reject the possibility of a theistic evolutionary origin of man (I am agnostic on that subject, not being persuaded that God ever intended to teach science in the Bible, and recognizing that it is easy to misunderstand what it actually teaches by reading it through modern filters). However, I do not believe naturalistic evolution, that humanity happened in essence by a complex accident; such a theory leaves no room for the validity either of moral imperatives or of reliable rationality. Thus I am presenting a viewpoint that is not my own, a position plausible for a strictly scientific viewpoint.
Under evolutionary theory, the proper function of any organism is ultimately to reproduce itself; any organism that cannot do so is dysfunctional by that definition. "Natural" homosexual intercourse is sterile: it cannot produce offspring. Any member of a species that is not part of the reproductive system in some way is dysfunctional; it will not pass its genes to the next generation as evolution requires.
The next issue would be the cause of the dysfunction. If, as the homosexual community insists, they are "born" this way, then they have inherited a genetic mutation not essentially different from sickle cell anemia or Crohn's disease, a disabling condition (in the sense that it inhibits them from performing the necessary biological function of reproduction) that cannot be repaired, and genetic counselors working strictly from an evolutionary ideology would properly recommend that they and their immediate family (who might be carriers) not reproduce for the sake of the future of the species.
On the other hand, it may be that the condition arises due to environmental factors. In that case, the possibility exists that it might be reversible--that is, homosexuals could be cured. Since we do not know the cause, we do not know whether it is curable or what kind of cure might be needed. If it is a learned behavior, psychological conditioning might avail. If there is a neurochemical problem, it may require the development of a class of drugs, analogous to lithium, which restore normal neurochemistry. If it does prove to be genetic (which is presently looking less likely) it might be incurable; even if not genetic, it might be a disorder we cannot cure at present levels of medical science.
Of course, homosexuals don't want a cure, any more than most alcoholics do. If it is an illness, it is one they enjoy. The fear for the species is that it might be contagious (particularly if it is not genetic), and if it spreads it impacts the propagation of the species.
All of this is based on an evolutionary value system. Such a system could be challenged. One might argue that there are species with non-reproductive members, such as bees and ants; such non-reproductive members, though, always serve the reproductive ones, not a desirable model for those who would be the non-reproductive humans. It could be argued that sexual relationships have evolved to have secondary functions related to social structures and bonding (I have so argued in another context), but these remain secondary and are valued in evolutionary terms to the degree that they promote the birthing and protection and development of future sexually reproductive members of the species. It could be argued, too, that sex is not only about reproduction, but is about pleasures and personal identities. Those, though, are fundamentally religious arguments--whether they are Christian or Hedonist or Pagan, they are outside the parameters of evolution, outside the hard sciences. They are value judgments about the place of sexuality in society, fundamentally "religious" in the sense that they argue about how the society "ought" to be. We can argue about what values have better basis in what philosophers call "natural law" (that inexplicably universal moral sense), whether we ought to do what promotes justice or what is pragmatic or something else, but let us not mistake a discussion of our preferences in values for anything other than a religious discussion--science does not offer values.
At this point we face the issue of whether one opinion is as good as another; but in legal terms, allowing homosexual sexual conduct is entirely different from promoting and subsidizing it, and the latter requires a basis in order to overcome the constitutional prohibition against government interference in sexual relationships.