Karl Popper wrote, in The World of Parmenides, (in Back To The Presocratics, from 1958 but edited again in 1989):
Here are the five fragments (DK B16 and 15; 18; 35; and 34) from Xenophanes’ writings.
The Ethiops say that their gods are flat-nosed and black
While the Thracians say that theirs have blue eyes and red hair.
Yet if cattle or horses or lions had hands and could draw
And could sculpture like men, then the horses would draw their gods
Like horses, and cattle like cattle, and each would then shape
Bodies of gods in the likeness, each kind, of its own.
The gods did not reveal, from the beginning,
All things to us; but in the course of time,
Through seeking we may learn, and know things better …
Popper is making a point about epistemology. I cut it off after the part relevant to my tangential comment.
Xenophanes may have be wrong about how other cultures thought about their Gods – which would, ironically, mean that he assumed others were more like himself than they really were. Popper should have known about and addressed this issue because it's part of the published literature:
Mythology: Timeless Tales of Gods and Heroes, by Edith Hamilton, 1942:
The Greeks, unlike the Egyptians, made their gods in their own image. Why it happened, or when, we have no idea at all. We know only that in the earliest Greek poets a new point of view dawned, never dreamed of in the world before them, but never to leave the world after them. With the coming forward of Greece, mankind became the center of the universe, the most important thing in it. This was a revolution in thought. Human beings had counted for little heretofore. In Greece man first realized what mankind was.
The Greeks made their gods in their own image. That had not entered the mind of man before. Until then, gods had had no semblance of reality. They were unlike all living things. In Egypt, a towering colossus, immobile, beyond the power of the imagination to endow with movement, as fixed in the stone as the tremendous temple columns, a representation of the human shape deliberately made unhuman. Or a rigid figure, a woman with a cat’s head suggesting inflexible, inhuman cruelty. Or a monstrous mysterious sphinx, aloof from all that lives. In Mesopotamia, bas-reliefs of bestial shapes unlike any beast ever known, men with birds’ heads and lions with bulls’ heads and both with eagles’ wings, creations of artists who were intent upon producing something never seen except in their own minds, the very consummation of unreality.
These and their like were what the pre-Greek world worshiped. One need only place beside them in imagination any Greek statue of a god, so normal and natural with all its beauty, to perceive what a new idea had come into the world. With its coming, the universe became rational.
Hamilton may be mistaken, but if so it's something Popper should have addressed. He reads like he's ignorant of the issue.
Wikipedia provides an indication of whether Popper should have known about this idea:
Edith Hamilton (August 12, 1867 – May 31, 1963) was an American educator and internationally known author who was one of the most renowned classicists of her era in the United States.
She got awards in Greece. I independently found her twice. First, other classicists mention her and I've read some books related to Greece. In particular I liked Greek Ways: How the Greeks Created Western Civilization by Bruce Thornton. The title is a reference to Hamilton's book The Greek Way (1930) which had the same theme: that the Greeks are our intellectual ancestors. Thornton's introduction discusses Hamilton and her importance and reputation, and the sources of some current opposition to her ideas in academia: postmodernism and multiculturalism (which are anti-Western ideas that also oppose Popper's thinking and values).
Second, I found Hamilton's Mythology book, quoted above, by searching for the best books to read on Greek mythology (which is the main focus of that book despite the generic title). It was highly recommended in several places.
Popper was an extremely hard and dilligent worker, and extremely well read – or so the reports say from various people who knew him. I would certainly have expected him to be familiar with Greek mythology and culture, not only Greek philosophers (I'd still guess that he was). It provides important context. Popper put so much effort into classics that he learned Greek to do it better. How, then, did Popper miss this? I'm no expert on Greece and I found it.
Internet vs. Library
Does Popper not having access to the internet at the time explain why he might not have come across this?
#15206 Yeah no internet makes things harder. But I think Hamilton was plenty well known for Popper to find her in a library or when speaking with classicists.
DeepMind's PYTHIA fills in missing characters in ancient Greek inscriptions
Tangent regarding ancient Greek: In 2019, DeepMind posted a paper about a program they wrote called PYTHIA that tries to fill in missing characters in ancient Greek inscriptions. PYTHIA apparently out-performed "two doctoral students with epigraphical expertise" in a test.