I don't see it as analogous to inter-racial relationships on earth and I think it's somewhat dangerous to draw that analogy, since the various humanoids of Trek have demonstrably different mental and physical abilities whereas humans share 99.9% of our genetic material and the differences found within races is greater than that found between them. Racism thrives on essentialist ideas that have been largely debunked. Careless SF analogizing is a way to sneak them in through the back door.
I do think Odo's love for Kira was somewhat silly, since he was an entirely different order of being and his humanoid appearance--presumably, his masculinity--was a convention he adopted, a mask. By analogy, I doubt that Shatner would have found Koko's attentions more welcome had he been wearing a gorilla suit.
As far as intelligence goes, a recent episode of House featured a total dick with an IQ well in the genius range who was married to woman with an IQ that put her just above being classified as mentally retarded. As the dick on the show--who was using cough syrup to dumb himself down nearer to her level--said, she was closer to a gibbon in mental ability than he was to her and he said that screwing her w/o the benefit of the tussin would be bestiality.
It's kind of hard not to see them as races, though, as problematic as that can be. They talk and act and prance about so exactly like humans that the notion they're from another planet often seems completely identical
(...)
But; so. When dealing with alien species we inevitably make the racial/national comparison because it's the only real world one we've got - a different species to us is the baboon or the orang-utan or the gorrilla. But a group of people who are intelligent, who can talk back to us, and who have different ways and look different to us? The only point of comparison we have is a race or nation-state. Races and nation-states are also a conveinent source of stuff to pillage for ideas; which is why a lot of aliens in Star Trek look more than slightly like repurposed historical cultures (the Romulans glaringly so in "The Balance of Terror").
Which does leave us with a rather festering can of worms, I'll concede.
It's actually a shame that this issue was never discussed on the show. Personally, I see it as allegorical to same-sex, or inter-racial marriages.
But, you know, Star Trek. We live in a future where such prejudices no longer exist (...mostly), and so on and so forth. We did get the implication Spock had a difficult childhood because he's inter-species, but that's about it. Maybe an episode about the prejudice felt about people from Planet A about marrying with people from Planet B, I guess.
The "inter-species" relations and relationships in Trek (and a lot of SciFi) have always been used as a metaphor for human ethnicities/nations. ( Nichelle Nichols remarked that she related to the character of Spock as someone with an experience similar to African American people of mixed black and white ancestry.) And personally, I don't find it problematic. Biologically, the concept of human "races" is outdated - even though the word still survives in everyday use and in demographic surveys. We can presume that the concept would be completely abandoned in Trek future in a few centuries. But by that time, the Trek humans are dealing with aliens, people who actually do belong to a different race of beings - so it makes sense to compare these inter-species relations and relationships to the relations between "races", ethnicities, or nations in Earth history: only this time, there actually is a biological basis for such divisions, since these people are really biologically different from each other, which was not the case with different groups of humans.
I don't really like the term "inter-species", though, because, frankly, the humanoids in Trek too often don't really seem to be of different species: they're too similar, and they can have offspring, who can have offspring of their own. Sounds more like sub-species.
As for the science of it all... oh, screw it.
There's real science, and then there's Trek science.
The only cases of relationships in Trek that can really be called inter-species are cases like Odo/Kira, a Changeling and a humanoid, where crucial biological differences actually do exist. Other than that, I think Laas put it well: "He has bumps on his forehead. She has a wrinkled nose. But they're basically alike. They're bipeds that eat, sleep, breathe."
I don't find the Odo/Kira relationship silly. The show didn't shy away from the fact that they belong to very different species, and that being in humanoid form and doing things that humanoids do is not something that comes naturally to Odo, not the way that linking does. Although I think more could be made of the constantly ignored fact that Odo was not biologically male any more than the so-called Female Founder was actually female. The show emphasized Dax as a trans-gender/transcending gender character, but when you think about it, the Founders are an even more interesting case, since they are sexless and could be any gender they chose to be. This could be regarded in two completely different ways. One might say that people - fans and writers alike - can't see past appearances, and are quick to assign classic male/female gender roles to everyone: so if a character is played by a male actor, everyone thinks of it as a man, and vice versa. Or, you may say that the fact that none of the characters in the show, including Odo himself, never doubts Odo's maleness, could be seen as a most progressive message about gender that Trek has managed to convey - a Founder does not have a
sex (physiological and biological characteristics of being male or female), but can have a
gender (a socially constructed role), and Odo clearly has the latter, which has become an essential part of his identity. (Unlike the "Female Founder", who, I presume, is only assuming female gender in order to be more appealing to Odo.) In other words - you are not less masculine or feminine, just because your gender is something you have
chosen, rather than being born into?
As for Odo's feelings for Kira - he wouldn't have the sex drive so he wouldn't desire her the way a humanoid male would, but love is not the same thing as sex drive, and... was it possible for Odo's love for Kira to become similar to our idea of romantic/erotic love? I think it was. Consider this: he had spent his entire life among humanoids, emulating their appearance and behavior; when he found the people of his own species, he was sorely disappointed and outraged by what they were like and what they were doing, and preferred to live with the solids; he was an outsider and felt lonely all his life, even more so after meeting the other Founders; Kira had been his best if not his only friend for many years, the person he felt the closest to. It's easy to see why he loved her, as a friend, at least. The first signs of Odo wanting to be more than friend to Kira was in "The Collaborator" when he seemed to feel a pang of jealousy when Kira told him she loved Bareil. While Odo does not naturally have sexual feelings in the usual sense of the word, and might really have found that part of humanoid existence puzzling, he secretly longed to be as close to Kira as possible, and it was painful for him to realize that other people can have the kind of intimacy with her that he didn't think he could, and that she could love them in the way she couldn't love him (or so he thought).
IMO it is not really that surprising that he would start to feel a desire to be closer to her and be loved by her in that way, especially after deciding he didn't want to go back to the Great Link. But we still see him torn between his deep love for Kira and the more "natural" call of the Great Link. He may also have had doubts about their relationship because of the things he knew he couldn't give her - there's a really telling moment in "Tears of the Prophets" when you can see a pang of pain on his face while Bashir is talking about the possibility Dax and Worf having a child; we don't know if Kira even wants to have a child of her own (she did carry Kirayoshi to term, but he is still Keiko and Miles' child), but I'm sure Odo has considered that he might want it in the future, and that's something she could never have with him. I think all this might have contributed to his decision to go back to the Link.
I rewatched "Ensign Ro" this morning, and what struck me was the absurdity of people reacting to the idea her name order was different from the norm.
You know, forget the fact that's how names are ordered in the Far East
Hungary, too. It's not really that unusual, and people on Earth have had all sorts of naming traditions throughout history, so it is really silly to have 24th century humans so surprised at the naming conventions of the Bajorans.
and she definitely didn't - she even thanked him for showing her how lame the solid version of intimacy was. 
) sex comic anthology), literally, attraction to the "different", the "alien", the opposite of xenophobia.
