I'm not surprised. People had so much free time to figure stuff out. I mean most of our knowledge is from people just sitting there trying to figure stuff out. Thousands of years ago you didn't have internet, tv, radio or any other mind numbing distractions.
Cool. The question that I have is how did they get the tabletop stones in place after two had been fitted vertically?
Same way he lifted the stone 3 feet to start the slide, also digging suggest that they may built dirt hills temp to get started toward the top. Regardless, incredible achievements with common sense.
This is real cool! I remember seeing a special on TV about someone near Homestead, FL, who made a large structure out of pieces of coral using simple principles like this guy. Some of the pieces of coral (upwards of 10 tons) rotate on a single bearing.