Pyramids built by man or extraterrestrials? Forbidden archeology

Step pyramids or pyramid-like buildings were built in ancient times at different times on different continents. Researchers now believe that between the different cultures separated by great geographical distance no connection existed, but that tribes living far apart these buildings are built entirely autonomous and independent. There are different theories about the origin of these customs. 
See also http://www.facebook.com/pages/Verbotene-Arch%C3%A4ologie/109481965747829