sdi

More Theosophy: Gottfried de Purucker agrees with you when he writes (in the Studies in Occult Philosophy): "No human being ever incarnates as a beast [for] there is absolutely a mental-psychical barrier preventing a human mind from entering a beast psycho-vital apparatus. [...] On the other hand, when a sorcerer, or a man of continuously evil life, through many, many incarnations on a steady downward grade, grows less and less human until the rupture with the spiritual and human monad takes place, [such] an abandoned vehicle is attracted to beast-bodies and even to plant-bodies. [...] Yet this is not [...] the incarnation of a human being, because such a degenerated, disintegrated, semi-annihilated human quaternary is no longer really human. [...] Such cases of degenerate human quaternaries, while fairly numerous in actual fact, are nevertheless quite rare or infrequent when compared with the immense number of beings forming humanity."

It seems clear to me from Sallustius, you, and from the various authors discussing reincarnation that I'm missing some vital piece of information.