Essentially, what if Polynesian peoples had kept up some form of contact with their urheimat in Taiwan or Malaysia, as well as between islands, and also built up long-term relations with South America, into the time of the Ming Dynasty (if it isn't butterflied away), when Chinese ships could be sent east.
I'm thinking that it could result in the creation of a script of some sort, maybe initially for trade but that later trickled into the rest of society. I could also be entirely wrong.