@jeremycherfas Is there a particular direction you're looking to go? For some of the underlying additonal proof in a similar direction, I'm still reeling at Lynne Kelly's Knowledge and Power in Prehistoric Societies (Cambridge, 2015) though her book Songlines with Margo Neale may be closer in tone and a bit less "academic". If you haven't read it, Walter Ong's Orality and Literacy is fascinating.