Vargr weakness

For what it's worth, the list of recognised Minor Human Races (so not including Variant Human Races, chimera, etc.) that I put together currently comes in at just under the 49/50 number (43, actually), with a few blank spaces for player/referee invention (and the Fiorin and Ilurian basically being just names that are only implied to be Human races, so can fill that role anyway).

Anakundu (Old Expanses): Not certain how easily they interbreed; given their short lifespan and awe of Vilani longevity, one assumes that if Vilani are compatible with Anakundu then that fact, along with the massive population disparity, probably means that pure Anakundu are rare by the time of the Third Imperium, assimilated into "Imperial Man".
Answerin (Vland): As GypsyComet says, it is reasonable to assume that even if interbreeding is possible, pure Answerin lineages were valued. I imagine that if they are compatible, there are pockets of Answerin genetics scattered across Imperial space. Answerin itself is probably reasonably distinct still, genetically.
Ayanshi (Reaver's Deep): Quite isolationist, don't interbreed; I imagine there would be metabolic issues if it was attempted?
Azhanti (Antares): Probably too distinct genetically to easily interbreed
Cafadans (Corridor): Low population, stay on their homeworld, so likely irrelevant to interstellar human genetics (sorry, Cafadans)
Cassilldan (Antares): Probably can interbreed with Vilani and Solomani; it's implied that they're a notable bloc much like Geonee, Suerrat, Darmine, Luriani, etc., so either way there's probably a fair few "pure" Cassilldan.
Darmine (Zarushagar): Can interbreed with Vilani and Solomani; percentage of pure Darmine among Darmine populations is unknown.
Daryen (Spinward Marches); interbred with Solomani to some extent
Dynchia (Leonidae): Very distinct, likely not compatible with other humans
Fiorin (implicitly, Third Imperium)
Floriani (Trojan Reach). Actually a constructed race of "biological androids"
Geonee (Massilia): Seem to remain distinct from Vilani and Solomani, probably not easily compatible.
Ghenani (Vanguard Reaches): Isolated on homeworld, which is relatively distant
Halka (Trojan Reach): Might have interbred with Florian League Vilani/Solomani minorities to some extent? I can't remember whether their compatibility was established.
Hanen (Gushemege): Probably incompatible? They have a large population but on a single world.
Happirhva (Reaver's Deep): Probably not compatible
Iltharans (Reaver's Deep): Not very fertile at the best of times, but probably compatible? Their world's fauna isn't very distinct from Terra's, I don't think any changes to their genome were too drastic.
Ilurian (implicitly, Third Imperium)
Irhadre (Lishun): Probably somewhat compatible? A bit of a controversial member of the Imperium, so somewhat at arm's length from the mainstream, which might account for their not being sucked into Imperial Man's genericness.
Issugur (Foreven): Not sure
Kargol (Leonidae): Neanderthal-derived, don't appear compatible with Solomani/Vilani.
Kedepu (Arzul): Described as interbred with Arzulan (that is, mixed Solomani-with-bit-of-Vilani) Humaniti.
Kukhunan, AKA Lancian (Gushemege): Seem to be compatible, indeed barely distinct from Solomani or Vilani anyway.
Liberts (Diaspora): Reference has been made to interbreeding with Solomani-Vilani.
Loeskalth (Gushemege) Only genetic remnants remain (so they only make this list controversially), but that shows that, yes, they were compatible.
Luriani (Ley): Distinct species but medical procedures can result in viable offspring (and families are often a mix of biological Luriani and culturally Luriani Solomani or Vilani anyway)
Mal'Gnar (Beyond): Isolated on homeworld
Murissi (Hlakhoi): A line in "The Deep and the Dark" suggests some cross-breeding with Solomani is possible, though whether that requires medical intervention we don't know.
Ne Kraeda ren Kelva (Far Frontiers): I know there's some backstory about this, I can't recall it off the top of my head.
Pirian (Gakghang): Compatible, I think.
Ronnin (probably) (Vland): The wiki extrapolates from the source to suggest that they are *probably* a distinct Human race, but it's not clear and either way they've interbred with Vilani, which is the only reason their small population hasn't died out.
Suerrat (Ilelish): Not compatible
Swanfeh (Gateway, though originally from elsewhere): No idea. I'm guessing compatible.
Sydite (Ley): Too derived to breed with other humans.
Syleans (Core): Interbred with Vilani and Solomani, pure lineages also remain
Tapazmal (Reft): Not sure, but as Darmine are compatible, I'm guessing they are too.
Tekundu (location unknown, implicitly Third Imperium). Probably not.
Thaggeshi (Vland): Both quite diverse and not far removed from Vilani-Solomani norms, so likely quite interbred with the mainstream.
Urunishani (Antares): Unknown
Vlazhdumecta (Far Frontiers): Apparently compatible with medical treatments; history of tweaking their genome since the Ancients were a bit sloppy apparently.
Yaskoydri (Coreward fringe of Charted Space, extra-Charted): Not sure.
Yileans (Gashikan): Heavily interbred with Vilani and Solomani, less than 5% of the Third Empire of Gashikan is pure Yilean, though most are part-Yilean.
Ziadd (Dagudashaag): Neanderthal-derived, not compatible with Vilani or Solomani (I wonder if they're somewhat compatible with Kargol or even Suerrat; the latter are relative neighbours?)
At least one Hive Federation member race (unnamed), possibly more than one.


Whether the Lamura (the Human half) are a Minor Human Race or descendants of Vilani, I can't remember (has either been confirmed?)
The Nullians (Hinterworlds) claim to be a Minor Human Race, but this is unconfirmed and they are perhaps more likely of Solomani-Vilani descent, dating from the Long Night.
The Saanshakase are descended from a transplanted Human population, but their actual original ancestry is unknown.

Pushing Up The Daisies and Having Joined The Choir Invisible:

(Solomani Rim)
Khulan (Vland)
Menetha (Kilong)
Miyavine (Dagudashaag)
People of Tanny (Massilia)
It is interesting to look at this from a primatology angle and think about what Vilani would look like. Europeans and Asians share a common ancestor about 40 thousand years ago and today are pretty distinct in appearance. Vilani and Solomani were separated 300,000 years ago. This is pretty much at the very beginning of Homo Sapiens and, whew, that is a lot time. Both could trivially pick each other out in a crowd. Personally, I would have picked 100,000 years ago to use Homo Sapiens Sapiens, but I think drawn out timelines is just an early sci-fi thing.

Vilani Differences
PACEC - Post Ancient Contact Evolutionary Change

Retain lactose intolerance (no livestock and PACEC)
Retain dark skin pigment (brighter star)
Retain dark irises (brighter star)
Retain dark hair (brighter star)
Retain prominent brow ridges (brighter star)
Lack blue eyes (cold/dark climate PACEC)
Lack red hair (Neanderthal contribution PACEC)
Lack resistance to any zoonotic diseases (no biologically related animals of any sort and PACEC)
Same height (taller for warmer climate but smaller for slightly higher gravity)
Straight haired (debatable - warmer climate versus coastal habitats versus hominid evolution and possible PACEC)
Develop less facial hair (warmer climate)
Develop less body hair (warmer climate)
Develop smaller eyes (brighter star or Vilani are nocturnal and develop larger eyes and smoother faces)
Develop smaller chin (300k years of only processed food)
Develop smaller/vestigial teeth (300k years of only processed food)

Historically we could expect four to five large Vilani genetic groups, but early technological development along with wars could have collapsed them back into one.

Demographic wise... Well, if I am space opera mode where technology is magic, then the Vilani and Solomani have blended together and are indistinguishable or have magically evolved in lock step despite being separated by hundreds of light years for 300,0000 years. Done. In scientific mode, well... 300,000 years. Would they have even found each other attractive to begin with? All that genetic drift makes offspring an uncertainty as well. But, we are going to assume that they do the nasty. In the Core, the Solomani genetic contribution would be minuscule. The only would you would know would be distant genetic traits resurfacing ("Hey mom, I got blue eyes just like great-great-great-granddad") or going to the Vilani version of 23andMe. To find Solomani, you'll need to head to the periphery where the pendulum swings the other way. On worlds originally settled by the Vilani, their presence would fade due to the ease of travel from Terra and also any impact from disease. A disease outbreak on a border would could very well kill everyone it would kill before word of it reaches an agency and then can prepare a proper response. I think disease would be the only way to get a equal mix of Vilani and Solomani. As Terran forces conquer the Vilani empire, they leave disease in their wake for which the Vilani are unprepared. Also, we are talking about modern people rather than 13th century farmers. People will be having children hopefully at least at replacement levels (rather than much less).
When the Ancients visited Earth there were several human "races". Sapiens, Neanderthals and Denisovians, plus the Erectus and Heidelbergensis and a few others.

Modern "Europeans" contain Neanderthal genes, while Asians are a mixture of Sapiens, some with Neanderthal, some Denesovian, some with both. Sub-Saharan Africans contain only very small amounts of these other genes, likely a result of... well best not to go into that.

Then there are the Polynesians and Austrailian Aborigines which may contain traces of hobbits still but those studies are contentious to say the least.

In the 57th century we only know for certain that the Zhodani evolved from the basic stock the Ancients transplante, with two distinct branches. Modern Zhodani evolved from them.
But you get into the tricky situation where the Ancients needed to know how Terrans would turn out to grab the right hominids in the right numbers. Technically doable if they had stuck around for longer than they did. Oh yeah, the thing we won't talk about. A pity that Africa doesn't preserve DNA evidence as well as colder climates.