Even the worst possible environment...say, repeated concussions to the head via a hammer, will still result in a human scoring far above any non-human.
I'm pretty sure you're wrong. I think research suggests that dolphins, parrots, bonobos and some other animals have tested higher than humans.
At standard IQ tests? Surely the creature doing a a standard IQ test needs at the very least opposable thumbs?
There will of course be exceptions, but a brain damaged but somewhat functioning human will always score better than a non-human at human-designed intelligence tests.
The argument isn't that a dolphin or bonobo isn't potentially smarter than a brain damaged human, but that by designing our tests for human use we are explicitly excluding non humans.
What are you trying to point out? That IQ tests as they are written for humans are biased in favor of humans?
Intelligence between humans and animals can (or could) be compared, but--like when testing between human populations--you wouldn't use a test that is so heavily biased against one of the groups that they can't even attempt it.
I'm pretty sure you're wrong. I think research suggests that dolphins, parrots, bonobos and some other animals have tested higher than humans.