Evidential Language

My son sent me this linguistic tidbit from Barking Up The Wrong Tree:

Tuyuca requires verb-endings on statements to show how the speaker knows something. Diga ape-wi means that “the boy played soccer (I know because I saw him)”, while diga ape-hiyi means “the boy played soccer (I assume)”. English can provide such information, but for Tuyuca that is an obligatory ending on the verb. Evidential languages force speakers to think hard about how they learned what they say they know.

Since most of my posts are way too long, I'll just let you ponder the significance of this on your own. (Tuyuca is spoken, it says, in the eastern Amazon. Ethnologue says there are about 815 speakers in Columbia and Brazil.)