re: tube
The ancient Americans were some of the most advanced astonomers of their day. They were also acomplished mathmaticians. That they may have lacked Europeans and Asian in metalurgy and other technologies doesn't imply they were primative. The Olmec/Mayan/Aztec calendars were far superior to the European calendar. It's a shame the Spaniard destroyed so much of the Mayan writing. I think we might be surprised with all they knew.
Dave M