Yes, but the human notion of "race" is just "people of a certain color". In dogs, this would group black yorkshire terriers and black labs together.

Furthermore, dog breeds are nothing like ordinary human populations. We simply don't have human populations that are subjected to the extreme selection pressures that we apply to dogs, which produce breeds with strong natural talents and lots of natural deficiencies that would kill them if they were turned loose in the wild. Chihuahuas versus Great Danes. People vary, and natural selection matters, but it's nothing like dog breeds.

Would you say that "Dog breeds, genetically, does not exist?"

Whatever you mean by that, it is pretty clear that it makes sense to talk about Caucasian race (or terriers) and use that concept, even if the manifested features vary.

No, it doesn't make sense to talk about Caucasian race. There isn't enough genetic difference between any human populations to divide humans into subspecies or races, unlike for example dogs. Humans have the least genetic variation of any mammalian species, so you can't make the dog comparison anyways.

Furthermore the name was created on fallacious premises to begin with. From the creator of the "Caucasian race" Johann Friedrich Blumenbach:

Caucasian variety - I have taken the name of this variety from Mount Caucasus, both because its neighborhood, and especially its southern slope, produces the most beautiful race of men, I mean the Georgian; and because all physiological reasons converge to this, that in that region, if anywhere, it seems we ought with the greatest probability to place the autochthones (birth place) of mankind.

How much genetic difference is enough? It is obvious that there is a grouping of features beyond skin color. Where you put the line between races is somewhat arbitrary - and this is the same with all concepts, so it doesn't make sense to think about genetic difference (e.g. in Rwanda Hutu and Tutsi are considered different races, even though genetic difference is almost inexistent http://en.wikipedia.org/wiki/Origins_of_Tutsi_and_Hutu). People have established this concepts because they are/were useful, and will continue to use them.

Right, but no one here is arguing that humans don't exist . . .