Ancient Alien Question: From UFOs to Extraterrestrial Visitations

Have we been visited by extraterrestrial beings? Did these "ancient aliens" contribute to the birth of human civilization? Do our ancient monuments contain evidence of their presence? Have we been visited by extraterrestrial beings? Did these "ancient aliens" contribute to the birth of human civilization? Do our ancient monuments contain evidence of their presence? Have we been visited by extraterrestrial beings? Did these "ancient aliens" contribute to the birth of human civilization? Do our ancient monuments contain evidence of their presence? Have we been visited by extraterrestrial beings? Did these "ancient aliens" contribute to the birth of human civilization? Do our ancient monuments contain evidence of their presence?