Similar questions have been asked. Try a Google search of site:reddit.com/r/askhistorians "ancient aliens"

https://www.reddit.com/r/AskHistorians/comments/1ajb6b/ever_since_ancient_aliens_was_thoroughly_debunked/

https://www.reddit.com/r/AskHistorians/comments/7u1vm7/ama_pseudoarchaeology_from_atlantis_to_ancient/

https://www.reddit.com/r/AskHistorians/comments/vhxcg/is_there_anything_historically_reasonable_about/

https://www.reddit.com/r/AskHistorians/comments/1na4w1/what_is_the_most_concise_way_to_shut_down_an/

https://www.reddit.com/r/AskHistorians/comments/1ovugj/how_do_you_disprove_the_claims_in_ancient_aliens/