the minmatar have their tribes, which have distinct and definite differences in appearance and culture.
and have maintained this, despite difficulties such as any blending during enslavement, or the whole emigrants/immigrants to/from the Federation, or other such things, such as a global/interstellar culture which would tend to promote mixing.
which to me suggests they are possibly a lot more picky about relationships than others.
e.g. the two caldari bloodlines look very similar, you can't say "that's a Civire, that's a Detei", but you can pick out the different tribes a lot more easily (although that may just be an accident of art direction).
A lot here depends on whether you believe that the tribal bloodlines
have been maintained. Ken's plausibly suggested, in his hitchhikers' guide, that the "tribes" are post-Rebellion inventions, complete with official origin stories based on murky tales and wishes. I'd take that further and suggest that the visually-apparent "tribes" might be the result of Amarrian breeding for certain types of work, much as you can tell a Great Dane (boar hunting) from a Border Collie (herding) from a Bichon Frise (companionship).
(One of the possibilities of this view, by the way, is that Sebiestor are generally so pale because most of them are genetically at least half True Amarrian, while the Vherokior are a blend of Matari bloodlines and Khanid. Against that theory is the difference in the life expectancies that were once offered for "Minmatar" and "Amarrians": it'd be interesting to see the Minmatar life expectancies broken down by "tribe" and "slave/free" status.)
(Another possibility is that the Amarrians took slaves from the Matar continent of Mikramurka to Bhizheba, for instance, and then got a bit superstitious about mixing the lines, so tried to source further stock which shared the characteristics of the first lot.)
I'd be very surprised if it turned out that enslaved Matari had intentionally managed to maintain tribal bloodlines through 700-800 years of slavery. That would be a very different model of slavery to the
familiar Earth patterns: more akin to occupation than slavery, perhaps, which would be
possible for some portions of the cluster but hard to reconcile with other parts of what we've seen.
(
Detour: Do we know anything about Amarrian technology, culture, and attitudes surrounding birth control? I realised after writing that earlier post that my assumptions about slavery and genetics were forged in times of relatively unreliable birth control. If the done thing is to feed female slaves the local equivalent of RU486 any time their bleeding is overdue and they haven't been put to an approved stud -- and to vasectomise
Louella's mancubines -- AND if it's somehow a contamination to mix the elevated Amarrian bloodlines with lesser races, then there might be less genetic mixing than I assume. That still doesn't argue for Minmatar control: the studs used over slaves would most likely have had the qualities their Amarrian holders and managers wished to encourage.)