I think it's fair to say that if we ever put a full human being into superposition with a large enough environment for decoherence to happen within the experiment, many worlds is all but confirmed.
It's interesting to consider the implications of this line of thinking though; it seems like it would imply that causally-disconnected regions of spacetime (i.e. things outside of our light cone) are forever in a superposition of all possible quantum states, from our perspective, among other things.