]My impression is that that that the Altha were "seed stock" for the universe. The Ka'ta'viir were a unique sub stata of the Altha that were senstive to the Essaence? That might not have been completely addressed in Spacemaster, but it parallels Niven's Ringworld? This is all built out of late 70's and early 80's?
I have not checked SM in a long time, but I think there was a number of hints that the Altha were the Sianetic Harbinger, the "seeder race" of the universe - which does not mean that they seeded it with their own genetic template, especially if you see what they did on Kulthea. The Kulthean timeline indicate that the Altha were a conquering race, so they might have found suitable genetic material somewhere and transplanted it on numerous planets to create slave races for colonisation (and cattle for the meat grinder of galactic warfare when needed). The K'Taa'Viiri were, once again from the Shadow World timeline, an Althan clan that had particular proficiency in Essaence manipulation, but since Essaence is singular to Kulthea, they must have had other advantages to rise to such prominence (wealth, psionic mastery, you name it).
And yes, Space Master is "heavily inspired" by the main sci-fi trends of the time. There is something timeless in the idea of a stellar "empire" with "noble houses" jousting for power with an established church as arbiter (and player at the same time) and a merchant's guild to round up the usual suspects, while aliens prowl the border and an "ancient race" still lurks in the dark of space. It's nothing original, even for sci-fi RPGs.