“These people had no blueprints to work with, nor, as far as we know, any previous experience at building something like this,” says study co-author Leonardo García Sanjuán, an archaeologist at the University of Seville in Spain. “And yet, they understood how to fit together huge blocks of stone” with “a precision that would keep the monument intact for nearly 6,000 years”.

They absolutely would have had prior experience if fhe process is complex. Humans tend to have bursts of developing new techniques sprinkled around, but a complex structure would be rhe result of combining existing knowledge in a new way with a few new techniques. They wouldn't figure a bunch of things out at the same time and build something to last thousands of years. They probably built similar structures that didn't hold up as well first and learned from it.