"BRAZIL'S PIRAHÃ TRIBE
Living without Numbers or Time
By Rafaela von Bredow
The Pirahã people have no history, no descriptive words and no subordinate clauses. That makes their language one of the strangest in the world -- and also one of the most hotly debated by linguists."
I heard about these guys a while ago, it's very very interesting, and brings up some interesting problems for linguistics as a whole. If you're remotely interesting, go and read this.