There is also this implicit form of -ism built into it, in that certain groups of people were "obviously" less intelligent so it is unlikely they could ever build something magnificent or intellectually obscure. Whether it is a belief that aliens must have built Mayan or Egyptian Pyramids because of a bias that they were dumb savages, or whether it is dismissal of alternate forms of successful government and social organization in "uncultured" parts of the world.

It is easier to assume something like "this mechanism shouldn't exist" if you (general "you") think a group of people are already beneath you due to your implicit biases.