[Allod]

I think that as far as in-universe explanations go, Heroka Vendile has already summed it up perfectly. Nothing to add.

That being said, maybe ethnicity doesn't crop up in a lot of novels (not only Black Library ones) because it doesn't really tell you anything about a character? It's like nose-shapes - usually they simply do not matter, unless you want to create the clichéd "hawk-nosed investigator" or crap like that.

Thirdly, and this is a purely personal opinion, I would sure hope that "ethnicities", as hard to define as they are even today, would be gone in 40,000 years' time because people on the whole finally started not to look for a mate of the "same" ethnicity as a priority.

[Inquisitor Sargoth]

Has nobody mentioned the fact that, with the odd exception (Salamanders, Raven Guard, Night Lords) - due to genetic defect, hence inhumanly pale/dark skin, black/red eyes - space marine skin colour actually changes to adapt to the local conditions? As they spend most of their time on starships or wearing helmets, they'd probably be pretty pale most of the time.

[Draco Ferox]

I would like to point out that it doesn't matter what skin colour a Krieg guardsman has, as they all wear the exact same faceless rebreather, which covers their skin, and in all of the pictures I can find of them, they wear gloves- it's a bit silly to have a heavy NBC proteacted trench coat, an gas mask, and everything-proof boots, only for your hands, one of the most vital parts of a soldier, to be exposed to all of that nasty stuff the Krieg regiments tend to slog through.

Besides, this can lead to the awkard situation where the black guy dies first:
http://tvtropes.org/pmwiki/pmwiki.php/Main/BlackDudeDiesFirst

[TallulahBelle]

I have always seen the bl;ack library books imply racial stuff with accent and clothing and build descriptions. the tanith I see as drawing from an irish influence and look for example with lilting voices whereas the chemdogs I see as being drawn from 70's new york I see race implied rather than stated plus racial discrimination wont really exist because Black and white will just gang up on green.

[DapperAnarchist]

The accent/clothing etc are cultural markers, not racial... also, I can't stand the "lilting voices" description of the Irish. We don't have "lilting" voices, as far as I can tell (what the hell is lilting, anyway? Going up and down?). We tend to have a sort of grumbly voice, rambling on like whatever....

While race, defined as skin colour, seems to have little relevance in 40K (though a frontier world or an isolated world could certainly begin a pogrom of all people with a certain skin colour on the claim it is a mutation, and thou shalt not suffer the mutant to live), race in the broader sense of a genetically related group distinct from other groups with the human species is definitely there - Catachans are all considered thuggish, dangerous, but reliable in a tight spot, Cadians are methodical, Galathamorians are religiously superior, etc... Never mind that that can't be true of all cases, these are the stereotypes the Imperial populace will hold, and they count as racial stereotypes.

[Dolnikan]

Most planets would be inhabited by a single 'race'. There is very little interplanetary travel and the Imperium's common people would in many cases assume that someone who looks different is a mutant, a bit like in our middle ages where people with other skin coloursa would be assumed to be very strange, add to that the fear of mutants and a pogrom is born. On some planets there will be a distribution like on earth, mostly planets where the mobility of people is low. When it is easy to travel the potentially different groups will mix to such an extent that they would become a homogenous group. Here on earth races developed when there was very little mixing of populations over longer distances, it was very unlikely for someone to mate with someone from another part of the world.

There also would be cultural stereotypes, even on a planet, like people from Hive Gamma are shifty, you can't trust them, those from two villages away are a bunch of retards, just like you see here on earth. Stereotypes about people from outside one's own group tend to be negative.

[Ancelyn]

This thread is still going?. Final comment from me, the Deathwing were based on native Americans. Thus demonstrating that Space Marines are not all caucasian.

[TallulahBelle]

science fiction relies on stereotypes for a lot of things race included, the cultural stuff is entwinned with race to talk about it I mean the vitrians were described as dark the guard in the book Imperial Glory are basically the ghurka brown skinned small, carry knives etc.