What I’m looking at is the shift from the larger and heavier percussion made atlatl projectiles of the paleo period to the more refined and pressure flaked projectiles of the archaic period when bow’s were in use.
When were bows in use? Dates I have are like 800 AD for Woodland Indians. That’s pretty coincident with the arrival of quetzelcoatl ~ try: http://books.google.com/books?id=qsYMEwmNP34C&pg=PA58&lpg=PA58&dq=bows+and+arrows+arrive+in+America&source=bl&ots=AJtmk6mlcq&sig=c4aIRSP-XYsLjXTlE9Im4PVkctM&hl=en&ei=ndJ0TYrzBIn4gAeorKGiAw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBcQ6AEwAA#v=onepage&q=bows%20and%20arrows%20arrive%20in%20America&f=false