How did ordinary humans build the pyramids or other ancient sites?

backbreaking effort, heavy loss of life. Upwards of 22,000 people died building the Panama Canal. And that was using "modern" construction techniques. While the actual techniques used have been lost to time, it is known that many thousands upon thousands of people were the laborers.

one stone at a time

ingenuity and muscle using engineering techniques

Slave labour with levers and pulleys.