I always wonder if this "no one wrote down vowels" thing was really because these languages were spoken without vowels. The issue with your theory is the numer

I always wonder if this "no one wrote down vowels" thing was really because these languages were spoken without vowels. The issue with your theory is the numerous counterexamples of languages from the same region which did not (and in fact still do not in plenty of cases) include vowel indicators in their writing systems, but nonetheless spoke and still speak the vowels. Also, Egyptian is known to have included "determinative" hieroglyphs for cases where the reading would otherwise be ambiguous; the determinative allowed words with the same consonant structure but different vowels to be distinguished from each other (though the determinative itself did not encode a vowel; instead it indicated what type or category of thing the preceding word was, which allowed the reader to choose the correct option). Plus your example of a vowel-less word is from a language which does have vowels: https://en.wikipedia.org/wiki/Nuxalk_language#Vowels https://en.wikipedia.org/wiki/Nuxalk_language#Vowels