In the Advaita Vedanta world, the only two beings who were officially declared as fully liberated by Ramana Maharshi were his mother and
Lakshmi the cow. So in this context, being human or animal makes no difference... perhaps because humans are animals. We share 90% of our DNA with cats. :)
The best advice I can give is to focus on the perspective of fully realised beings. Scholars will get lost in debates which are of no real value. The perspective of the sages is along the lines of "you are already in the highest state, you just can't feel it because you are identified with your mind." This message needs to be understood as an invitation to undergo a transformation in identity.
Hence the oneness doesn't need to be achieved, but we merely need to see the falseness of the human identity for what it is. That's ultimately what this whole game is about.