It mentions that this was a culture without written language. I wonder if that was important - once you develop writing, it might be easier to pass notes than invent this.
The Incas that followed them had recorded language. I doubt it is really known positively that Chimu had no recorded language. There are quite a few peoples groups in the western hemisphere for which it is commonly asserted by outsiders they had no recorded language, but once you start studying them at all, you find they have a recorded language.
