Maybe absorbing other creations in only possible for advance shapers, but since in all the genefore games so far, you start of as a novice, and only learn spells and whatnot, and not actually the regular things the shapers would be teaching you, and so you can't absorb other creation. Also, maybe you could absorb the artila in GF3 because it was a fairly basic creation, and for something with a strong mind like a servile, you might not be able to do that.