I've seen some of these, some are known to be fakes, and some could represent the sun or the moon which are most often circular. It seems to me that if something as advanced as a spaceship had appeared to primitive man, or even up until the 18th century or so in some parts of the world, that it would have been worshiped as a god, and it's legend would have grown to the point it would have it's own religion based on ancient lore. But instead there were other things worshiped, and more stories of dragons and giants than of objects flying through the sky at amazing speed.
I understand your perspective.