Unlikely, since we see that Big A was human all throughout when the humanoid animals met him, but then he left, because most likely he started to transform. Him being an animal beforehand wouldn't have made sense because the animals met him after they were traumatized.
Maybe the transformation happens both ways like animals turn human and human turn animal
Ooooh that actually makes a lot of sense and I also noticed fluffy as a dog but I didn't pick up that he transformed from dog into human . But it doesn't explain how Mr A had goat (or some sort of animal) ears so maybe there's a mix of humans transforming to animals and animals transforming to humans. That might also explain why some people like M and K didn't go crazy when they remembered their lives because they did actually have a life but other people that transformed into a human did go crazy and try to kill themselves because they were confused or shocked or something
They know their own backstories though. And remember changing.
My theory is just a theory, A GAME THEORY!
This is my theory
I think they are not human turn animal but animal turn humanoid. Fluffy seems to be that if we see last chapter as foreshadowing on Fluffy. I think what Little A see is animal human transformation and his parents didn't believe in him and thought he is insane or traumatized. So I guess the memory of the past is just make up stuff that animal believe they are