EDIT: TY /u/Kegaha Mankind, bad choice of word. To be more precise, the change from the Egyptian/Roman/Greek/Northern Gods to Christianity, Islam and Judaism.
If you don't mind, can you specify what you mean by "Mankind"? If you mean humanity as a whole, then I fear your premise is wrong, monotheism is not universal. Shintoism, Hinduism, ... Are polytheist religions that are still "common" nowadays.