You're right, IQ tests that are not literacy-based are inconclusive.
Look, 45% of Egyptians are literate, so they probably took a few hundreds of them, and that's what the average was.
You do not even need IQ tests to guess what the IQ of a population is.
Are you even surprised that Japanese people have a very high IQ on average, for god's sake, that's where our baldness cure will be coming from!
If you reject evolution, you might as well do away with all science.
And it's not a matter of belief at that point.