I don't even think intelligence itself is understood.we have very few things to compare human intelligence to. And there's many known cases of "less intelligent

I don't even think intelligence itself is understood.we have very few things to compare human intelligence to. And there's many known cases of "less intelligent" species accomplishing things that "more intelligent" species cant. (Eg. Humans cant organize like ants can, though ants cant do calculus as far as we know) So without knowing how to measure intelligence or what high intelligence is. I don't think I can have an opinion on if intelligence is fixed.