like i said, similar, in terms of a creature that doesnt need mutation to be cast on it. guinea pig simply has it as one of the possible effects in order to prevent it from being OP and in order to make it more interesting.
i just think that as is, this is still too powerful, as i understand it, this card would be played (immaterial so no risk of it dying), next turn a mutant would be created, over time the mutant would die, then spawn two minor ones with the ability to evolves into the original card and start the process over again. honestly i think it would be better if you simplified it some more. if it were me, i would cut out the generation of the minor things entirely, but its your card and thats straying from your original vision, just my 2e.