Different species can interbreed, at least in some cases.
But their offspring will not be fertile, unlike half-orcs and half-elves. A species by definition is a group of organisms that can produce fertile offspring.
I believe there are some hybrids that are fertile (although it seems it's much more rare than I had thought when I made that comment). After a bit of googling, I found the grizzly-polar bear hybrid, which is fertile according to a couple pages I looked at (although I'm not sure how reliable those pages were).
A species by definition is a group of organisms that can produce fertile offspring.
That's an obsolete definition, @Jalily, nowadays that's just a rule of thumb rather than a definition, because there are counter-examples in both directions (i.e. there are some distinct species which can produce fertile offspring, and on the other hand there are population groups within some species which can't inter-breed). Some dictionaries still offer this old definition, but they're now false-to-fact and need an update.
Defining precisely what is or isn't a "species" has turned out to be a more complicated problem than early taxonomists had realised, and biologists do not currently agree on any precise definition. (I'd guess that the microbiologists will eventually win the argument and develop a uniform definition based on DNA sequences rather than fertility, but that's only a guess.) The current muddle pretty much comes down to saying "I'm not sure what a species is, but I know one when I see one".
The definition of "species" does not fit here. Orcs and humans can interbreed, and half-orcs to my knowledge can also breed.
Ability to interbreed is not the definition of species, many real-life species can inter-breed (although usually with infertile offspring). It also turns out that some hybrids can even be fertile, so the old definition about fertile offspring is no longer valid either.
Consider: if ability to interbreed were the definition of a species, then by definition elves and orcs would automatically be simply races of the human species, not separate species. In which case, the game would be describing them as "not human" (which it very definitely does) merely because they're a different race. That's just about the most viciously racist thing it'd be possible to say! Fortunately it isn't so: they're separate species and therefore correctly described as not human.
Also, the terms race and species are often interchangeable in sci-fi and fantasy, especially in in-universe dialogue. Mass Effect will often refer to the turians, asari, and salarians as the "Council races," for example.
True, but I reckon it's inappropriate, incorrect and unfortunate. Just because this misuse of terminology is quite common doesn't make it right.
Besides, considering the wide array of things, people, age groups, and body parts real life humans are capable of fetishizing, the idea that a half-orc and a gnome could not possibly be attracted to one another is patently ridiculous.
I agree, in fact. Real-life shows that a small number of weirdoes do indeed find romantic attraction outside their own species: cases come before the courts from time to time concerning such people. For the overwhelming majority of us, however, even though we might be genuinely fond of (say) our pet dog, the idea that such fondness could become a romantic attraction is just sick.
I'll also agree that, since half-orcs and gnomes are both intelligent species rather than "dumb animals", there may be a larger possibilty that friendship might occasionally develop into some sort of romantic attraction, and it's not a totally sick idea like getting it on with your dog. Nevertheless, it strikes me as pretty darn unlikely, it'd be a rare and remarkable event because there'd be so little basis for compatibility. We all know from the real world that romantic relationships can often be difficult even between fellow humans, and with a non-human it'd be very rare for it to get off the ground at all.
Even between species which have more in common, such as humans and elves, I can't see it as plausible that there would be very many half-elves, although that's a much more credible relationship than a half-orc and a gnome. As for half-orcs, I doubt that we're expected to believe that most of them are the result of any "romance" between a human and an orc - orcs are nasty b@stards who don't care about the niceties of consent.
Don't embarrass yourself by attempting to impose your own preferences on a genre of media and literature that has already proven you wrong a hundred times over.
I'm not remotely "embarrassed", and I don't see why I should be. In the first place, I haven't actually said anything about my "own preferences", I'm simply arguing about what makes plausible fiction. Secondly, nothing in a genre of fiction "proves" anything, because it's fiction. Thirdly, the genre (and especially the more literate and thoughtful end of the genre) is full of warnings against the feasibility of successful romantic relationships across species boundaries, and successful examples in the literature are often held up as rare exceptions where severe difficulties have been overcome (think of Aragorn and Arwen, for example).
@Gallowglass The phrase "little basis for compatibility" strikes me as the crux of this issue. You cannot tell me that there is little basis for compatibility between, say, a half-orc and a gnome when there are literally real life people of average size who want to have sex with nobody other than midgets/little people/dwarves/whatever. What are we calling compatibility, here? Physical attraction and personality/chemistry? Physical attraction is not a concern, because everything is liked by somebody. Personality is hardly a concern, since every race is composed of sapient individuals that are capable of manifesting the same personality traits as any human. What exactly is not compatible?
The outright crazy number of interracial relationships in sci-fi and fantasy does prove something, that these compatibility/plausibility issues you're raising don't actually exist. To use Mass Effect as an example again, they've got turians dating quarians, humans dating androids, asari marrying batarians, and krogan females requesting to mate with Shepard. Aragorn and Arwen are clearly attracted to one another, and Gimli thinks Galadriel is the most beautiful woman that has ever existed. In BG2, one of the human male thieves in Aran Linvail's guild hits on a female halfling. There's a male gnome prostitute in the Bridge District offering his services to humans, elves, and half-elves. Viconia will romance half-orcs but will not romance elves. The examples go on and on.
@TJ_Hooker As Jalily pointed out, that's why I went into how half-orcs are not, to my knowledge, inherently infertile. Sure, a "liger" can be produced by impregnating a tiger with lion sperm, but the liger itself is infertile, and thus lions and tigers are indeed separate species.
@Elendar And you're still not over it. If only I could patch THAT.
Well, if all you care about is OMGWHYDORNROMANCESSMALLBEINGS then we really deserve to have bugs, an annoying process to add new soundsets, a pretty unfriendly portraits chosing system, kits and races not working as intended and be forced to use Hamachi to have a decent multiplayer experience.
I'll jump on the bandwangon of serious business: why does Imoen have purple cloths now??!!11!!1eleven!!one!
Well, IIRC, she will romance you if you're a Gnome (I guess she's fond of them because of Uncle Quayle's influence). And her romance may end up with her getting pregnant, so...
Comments
Defining precisely what is or isn't a "species" has turned out to be a more complicated problem than early taxonomists had realised, and biologists do not currently agree on any precise definition. (I'd guess that the microbiologists will eventually win the argument and develop a uniform definition based on DNA sequences rather than fertility, but that's only a guess.) The current muddle pretty much comes down to saying "I'm not sure what a species is, but I know one when I see one".
Consider: if ability to interbreed were the definition of a species, then by definition elves and orcs would automatically be simply races of the human species, not separate species. In which case, the game would be describing them as "not human" (which it very definitely does) merely because they're a different race. That's just about the most viciously racist thing it'd be possible to say! Fortunately it isn't so: they're separate species and therefore correctly described as not human. True, but I reckon it's inappropriate, incorrect and unfortunate. Just because this misuse of terminology is quite common doesn't make it right. I agree, in fact. Real-life shows that a small number of weirdoes do indeed find romantic attraction outside their own species: cases come before the courts from time to time concerning such people. For the overwhelming majority of us, however, even though we might be genuinely fond of (say) our pet dog, the idea that such fondness could become a romantic attraction is just sick.
I'll also agree that, since half-orcs and gnomes are both intelligent species rather than "dumb animals", there may be a larger possibilty that friendship might occasionally develop into some sort of romantic attraction, and it's not a totally sick idea like getting it on with your dog. Nevertheless, it strikes me as pretty darn unlikely, it'd be a rare and remarkable event because there'd be so little basis for compatibility. We all know from the real world that romantic relationships can often be difficult even between fellow humans, and with a non-human it'd be very rare for it to get off the ground at all.
Even between species which have more in common, such as humans and elves, I can't see it as plausible that there would be very many half-elves, although that's a much more credible relationship than a half-orc and a gnome. As for half-orcs, I doubt that we're expected to believe that most of them are the result of any "romance" between a human and an orc - orcs are nasty b@stards who don't care about the niceties of consent. I'm not remotely "embarrassed", and I don't see why I should be. In the first place, I haven't actually said anything about my "own preferences", I'm simply arguing about what makes plausible fiction. Secondly, nothing in a genre of fiction "proves" anything, because it's fiction. Thirdly, the genre (and especially the more literate and thoughtful end of the genre) is full of warnings against the feasibility of successful romantic relationships across species boundaries, and successful examples in the literature are often held up as rare exceptions where severe difficulties have been overcome (think of Aragorn and Arwen, for example).
The phrase "little basis for compatibility" strikes me as the crux of this issue. You cannot tell me that there is little basis for compatibility between, say, a half-orc and a gnome when there are literally real life people of average size who want to have sex with nobody other than midgets/little people/dwarves/whatever. What are we calling compatibility, here? Physical attraction and personality/chemistry? Physical attraction is not a concern, because everything is liked by somebody. Personality is hardly a concern, since every race is composed of sapient individuals that are capable of manifesting the same personality traits as any human. What exactly is not compatible?
The outright crazy number of interracial relationships in sci-fi and fantasy does prove something, that these compatibility/plausibility issues you're raising don't actually exist. To use Mass Effect as an example again, they've got turians dating quarians, humans dating androids, asari marrying batarians, and krogan females requesting to mate with Shepard. Aragorn and Arwen are clearly attracted to one another, and Gimli thinks Galadriel is the most beautiful woman that has ever existed. In BG2, one of the human male thieves in Aran Linvail's guild hits on a female halfling. There's a male gnome prostitute in the Bridge District offering his services to humans, elves, and half-elves. Viconia will romance half-orcs but will not romance elves. The examples go on and on.
@TJ_Hooker
As Jalily pointed out, that's why I went into how half-orcs are not, to my knowledge, inherently infertile. Sure, a "liger" can be produced by impregnating a tiger with lion sperm, but the liger itself is infertile, and thus lions and tigers are indeed separate species.
@Elendar
And you're still not over it. If only I could patch THAT.
I'll jump on the bandwangon of serious business: why does Imoen have purple cloths now??!!11!!1eleven!!one!
I don't get the indignation with Dorn romancing small characters. Aren't they allowed to be badass enough for him?
Size doesn't really matter. In the real world, little people are perfectly capable of maintaining physical relationships with normal-sized folks.
And if you're concerned about reproduction... well, go back to the first paragraph.
Now that's fowl.