in Final Fantasy IX, Gardland uses Soulcage to separate Gaian and Terran souls from the soul circulation process with Gaian Souls being stopped and ejected out of Iifa's roots as mist while Terran Souls are allowed to continue with the process.
Now obviously replacing every Gaian Soul with a Terran Soul in the process is a long process which is why Garland needed Kuja and Zidane to create conflict to speed it up, however the process has been going on for thousands of years and according to the wiki Terran flora and fauna are already showing up
1000 years ago Garland placed the Soul Divider at the Iifa Tree's base to discard the Gaian souls and replace them with Terran ones, thus slowly restoring Terra. Terran flora and fauna began reviving on Gaia as it was finally recovering from the destruction that happened in the wake of the failed Fusion. The discarded Gaian souls were sent off through the tree-roots to the continent where, by this time, a civilization had formed.
So i am wondering, are the varied non-monster species on Gaia a result of Terran Souls replacing Gaian ones? like say some of the species on Gaia at the moment of the game are actually Terran species? if so what species (or people) are actually Terran? (Excluding the obvious, Kuja, Zidane, Garland and Mikoto)