G'Naakbusters
Emperor Mongoose
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.
Uncertain:
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:
Harappan (Solomani Rim)
Khulan (Vland)
Menetha (Kilong)
Miyavine (Dagudashaag)
People of Tanny (Massilia)
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.
Uncertain:
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:
Harappan (Solomani Rim)
Khulan (Vland)
Menetha (Kilong)
Miyavine (Dagudashaag)
People of Tanny (Massilia)