Firstly (and I haven't the time yet to read the thread entire, so my apologies if this has already been dealt with - point me to the relevant posts and I can deal with them in turn), this presupposes that marriage already has a valid definition specific to heterosexuals (or, specifically exclusive of homosexuals). Given that you are pleading a biological basis for marriage, as below, that implies that no such definition already exists. Instead, it seems you are trying frantically to retcon in a definition of your liking so that you can protest that marriage is being 'redefined', rather than - as many would no doubt have - accept that the wide scope of marriage is merely being formally recognised. I'll deal with the validity of your argument from biology later on.
Secondly - under the racist/sexist views of previous times, the same arguments you are making do indeed apply to blacks or women. Just one example:
[original]"Gays already have the right to get married, just like straight people do. What gays want is to have the same results (gays and straights can marry any consenting adult), but under their own terms ("redefining" 'marriage between man and woman' to 'marriage between two people')"[/original]
[parody]"Blacks already have the right to drink from public fountains - just like whites do. What blacks want is to have the same results (whites and blacks can drink from any fountain), but under their own terms ("redefining" 'whites-only' and 'blacks-only' fountains to 'people-only' fountains)"[/parody]
As to your first paragraph, marriage has its significance <not definition> to society based on providing a value to society, hence the reason for its recognition by society. Marriage is the public statement <in society> of two individual's commitment to one another. Under any terms, this commitment of two people does not have any particular value to society. I and my accountant have a commitment to one another, as I do with my lawyer, but nether of this have any need to recognize society and establish and institution because of them. However heterosexual couples can produce offspring, and these offspring that are invariably, without exception, the product of heterosexual reproduction, are proto members of society and need to be brought up to be responsible members of society at adolescence, thereby becoming positive citizens in society, and establishing society's interest.
This interest is so pervasive and instrumental to society, that societies the world over, throughout mankind's history, have invariably recognized these committed heterosexual unions, despite being separated by time, and geography and having had no interaction. When Western Europeans finally reached the Orient, they discovered to no surprise that the societies there also recognized and institutionalized marriage between a man and a woman.
If Marriage were actually just whatever relationship between two people, then some society over mankind's history would have chosen some other mere tradition to recognize as critical to society other than man and woman, but this is not the case.
The fact is that gay relationships do not produce offspring, which do not then ever populate society, which do not need the extended, committed union to produce positive future citizens, and as a result gay unions are not recognized by societies, nor can a gay union every be the equivalent of marriage.
Marriage is not based on 'the fact of human biological reproduction'. Otherwise those who were infertile would not be allowed to marry - after all, they "cannot possibly produce offspring, and [are] incapable of populating society with offspring [they] cannot produce".
Marriage is not dependent on biology. It is a social arrangement, not a biological one. If you want to come up with a reason why marriage should be seen as 'straights-only', you're going to need a better one than that.
As a matter of fact, marriage is based on human biological reproducion, and we know this for a fact, due to its recognition in societies that have not had influence from or origin in other societies in tradition, thereby having a uniform recognition
Marriage does
not involve the any necessity or compulsion to produce children, but rather on that possibility, which is why fertility test has never been a prerequisite to enter into marriage, nor any sort of compulsion to produce offspring.
By your own fertility example, a same-sex union is also without exception "infertile' and incapable of producing offspring, and thereby there is no need to recognize that committed relationship before Society.
As a sideline, given that many anti-SSM are also pro-life, and a common pro-life argument favours adoption, you would think that increasing the number of couples who are willing to adopt and whom the evidence suggests will not be hindered as parents by their sexuality whould be a good thing for society...
For society to recognize and promote same sex unions because they are able to adopt, those societies would also be recognizing the breaking of biological bonds, and social bonds, as no same sex union has children within that union without the breaking of these biological and social bonds, thereby recognizing and promoting such would be destabilizing to society.
On an interesting side note, it is not surprising that Hillary Clinton and other Progressive Marxists, have promoted the idea that "it takes a village to raise a child", because the Marxist ideology is founded on destroying those very social bonds, and societal structure itself, to remake that society in its own image, and therefore undermining the importance of the marriage union is something they seek to accomplish.
In fact, on January 10, 1963, the Honorable Representative from Florida A. S. HERLONG, JR. read into the Congressional record 45 "Current Communist Goals" as indicated in "The Naked Communist." Among these 45 goals, were #16,"Use technical decisions of the courts to weaken basic American institutions by claiming their activities violate civil rights," #26, "Present homosexuality, degeneracy and promiscuity as "normal, natural, healthy, " #40, "Discredit the family as an institution. Encourage promiscuity and easy divorce," #41, "Emphasize the need to raise children away from the negative influence of parents."
Trip said:
The relevant example here is one I've previously given. If one state were to redefine Driver's Licenses as also applying to airplanes, and then tried to abuse the Full Faith and Credit clause to force every state to recognize those licenses for flying any plane in those states. This would obviously create a problem because those licensee's are really not qualified to fly planes, and are not the equivalent to pilots. If this License recognition were forced on every state, then every state and its citizenry would lose faith in plane pilots, and not want to get aboard planes. The result would be the destruction of the Airline Industry <marriage>, and the undermining of society.
That would only be a relevant example if:
a) Such a drastic redefinition had taken place in the first instance, which isn't the case - a more relevant example would be that when a new car comes out, the driving licence automatically accomodates it, even though the driving license was not granted with that specific car in mind.
b) Allowing gays to marry would somehow affect the marriage of straight people, which also isn't true. If you feel that allowing Jane and Wendy to marry each other poses a threat to your own marriage, then prehaps we shouldn't be taking lessons from you in what constitutes a 'stable marriage' in the first place.
Actually it is a relevant example because
a) A drastic redefinition of marriage does occur by the gross over-simplification of marriage to be merely "two people choosing to be together". Nowhere have societies the world over recognized marriage to be "just two people" because societies have absolutely no benefit from, or interest in, any two people choosing to be together. Your example is inaccurate because a driver's license does not automatically come with cars, or people, and validating any new vehicle with a driver's license, not the driver, does not serve the benefit of society, and rather provides a threat to that society.
b) It is not about individual gays marriages affecting individual people, or even collective gay marriages affecting individual people, but the fact that gay marriages do not provide offspring, do not populate and promote society, and therefore societies over mankind's history have not had any interest in the promotion and recognition of gay union, contrary to heterosexual unions. Overall, the devaluation of marriage and distortion of its purpose, not only indirectly devalues every marriage within society, but undermines society itself. This point is an invalid construct.
Marriage is not just recognized because of some haphazard "tradition", but rather the fact of biological reproduction, the needs of prolonged human development, and the interest of societies in their own promotion and advancement.