The Indo-Europeans who spread over most Europe and a big chunk of Asia 4-5000 years ago, left their traces not only in language but in religion and social structure. A cardinal element of social structure seems to have been division into priests, warriors, and farmers, a social structure that existed ancient Greece, Rome, Germany and Ireland, and persisted in attenuated form even into the nineteenth century in Europe. It continues to play an important role even in modern India.
The religions of ancient Europe all had similar elements, with the names and characters of gods, rituals, and legends sharing powerful commonalities.
One common god, especially prominent in Greek and Roman mythology, was the one denoted by the Indo-European for father sky. (dyaus pita in Sanskrit, Ju piter in latin, and presumably *dyeus pəter in Proto-Indo-European). In much of the world the old gods have been chased out by the congenitally jealous Semitic God, but the old traces are not quite gone. The Lord's Prayer opens with "Our father, who art in Heaven..." Sounds like a sky god to me.
The old I-E gods are not forgotten. Versions of most persist in Hindu religion.
From: In Search of the Indo-Europeans, by J P Mallory.