Idas about how Eywa could feasibly have come into existence

[Mithcoriel]

Why? What's wrong with favouring all creatures alike? Why do you think they should favour the Na'vi over their predators, but not the Yeriks over their predators the Na'vi?

As us humans have gained greater control over the environment, we've used that control to domesticate useful species and wipe out ones that are detrimental to us or to our domesticates. Why wouldn't the trees do the same thing? Gain control over the animals that are useful to them and wipe out the animals that hurt them directly or eat the animals in the first group.

Well evidentally that's not what the trees/Eywa are doing. By the time the trees were able to influence animals in such an extreme way, there was obviously already some kind of mind in place that cared about the balance of all life.
Also, I'm a bit puzzled as to how the trees could so easy wipe out predators and have so much control over the species.