not quite the same

Of course it's not quite the same. Neither is being stupid quite the same as being ugly. But do you really think a thing is only a real insult if it's about something that directly impacts your reproductive fitness? That seems a very odd idea to me. (And I question whether being intelligent -- as opposed to unintelligent, rather than outright stupid -- is a net benefit to reproductive fitness; I would guess that typical reproductive fitness is no worse at IQ 100 than at IQ 140. If you think "unintelligent" implies stupider than that, feel free to pretend I said "not especially intelligent" instead of "unintelligent".)