Did Imperial China, ca. 800, not view itself as more advanced than its neighbors to the North? Did the Aztec Empire, ca. 1300, not view itself as more advanced than the "dog people" to the north?
Can progress be defined in a culturally indifferent way?
As I wrote in your thread on /r/asksocialscience:
"Progress" is a normative assessment that we tend to eschew as historians. What is "progress?" What does it tell us? "Progress" is just a word that describes certain social, technological, whatever conditions of a society we decide to care about. But beyond simply describing them, it places a moral or normative judgment on them and labels them "good."
This is an historically un-useful thing to do.