First off, this was wonderful. Easy +1
Unrelated to that, I couldn't help but notice some connections to SCP-1427. Given that the name of the species here is different than the one discussed in SCP-1427, I doubt the author intended for them to be related. However, between the general connections in terms of time period and also the idea of nuclear fallout, I can't help but headcannon some connection between the two.
Perhaps Homo nobilis is a translation of what they called themselves while Homo descensus is what we named them. I could just be reaching way too far here, but it's these small connections between unrelated things on the site that often elevate the reading experience for me.