Ancient Structures and Smart Ancestors ?

Q. How could human beings without sophisticated tools or knowledge of engineering craft and transport or build such incredible structures? My theory: I think many people underestimate power of free time in your hands (including us on the Internet) and empty mind. Let's imagine world with - No stock market, no television, no internet, no porn channels, no comics, no advanced machines, vehicles etc. All that leaves on this planet to do some structures like pyramids, towers and palace, caves and other art stuff. It's that simple. You assume that ancestors were too smart. You also have to consider the point that ancestor were jobless or they were ruled by few people with mind or power, ego and have too many useless things to do in their lifetime. Let's apply this to prometheus, I am sure they took some humans on their ship to build temples or resting places. What do you think?