If we did on what grounds would we do so? Lower average intelligence? How exactly could we do that while granting similar rights to humans with equivalently low IQs?
It's hard to imagine that this wouldn't destroy modern liberal societies. We would either grant them equal rights at a huge societal cost, or start denying rights based on intelligence which would come at a huge ethical cost.
I think about this a lot in regards to extinct human species. I often wonder what would happen if we found Neanderthals hiding out on an island somewhere. What rights would we give them? Would we allow them to bred with humans? It seems every answer is wrong.
It's very, very rare for a human to have to prove mental competence for any reason. We let mentally incompetent people grocery shop and drive cars and vote, knowing full well they're a danger (or at least not a net benefit). Every town in every country contains well-known incompetent citizens.
What's the default for intelligent non-humans?
Does each one have to prove mental competence? At what level: that of an average human, or that of the lowest competent human?
Is the default to assume they are competent, and have all the rights and privileges of a human, or is the default to assume they aren't competent and don't have those rights?
Personally, it makes sense to me to err on the side of "any being who tells me plainly that they want a vote gets to vote".
Great questions, we will need some good answers soon. Not so much for the monkeys, but for AI.
What do you mean?