What is the justification for the belief that intelligence requires an immortal soul?

This question arose in the context of arguments about extraterrestrial intelligent species. Some Christians, especially among Young Earth Creationists, believe that we can rule out the possibility of ETs on the basis of Scripture. Anyway, my intention here is not to prove or disprove that, but rather on some ideas which have appeared within the discussion. This article by Gary Bates makes many arguments for that conclusion, and I'm wondering about one specific part of the argument, namely the assumption throughout that ETs must have immortal souls, just as we do (I know some schools of thought dispute this; those are outside the scope of the question). They bring up an idea from Michael Heiser that "Just like ‘bunny rabbits’ on the earth, they do not need salvation—even though they will die, they are going to neither heaven nor hell." The respond thus: > And Heiser’s ETs in spaceships require a level of intelligence not found in rabbits. This acutely highlights the injustice of their suffering the effects of the Curse, including death and ultimately extinction when the heavens are ‘rolled up like a scroll’ (Revelation 6:14). It also seems bizarre to assign no moral responsibility for the actions of highly intelligent beings. But this response is somewhat oblique - Heiser's argument isn't that they aren't morally accountable (at least not as presented by Bates), but rather that they don't go to heaven or hell. Bates seems to be a tacit assumption here that an immortal soul is a prerequisite either for intelligence or for moral responsibility. It isn't clear which, but in either case, I'd like to understand the philosophical underpinnings here a little better. **Have some Christian philosophers made the case that moral accountability and/or rational intelligence require an immortal soul?** If so, what reasoning is used to argue for that conclusion?