I believe that the ancient astronaut theory is true. Many civilizations of long ago all have their own stories and mythology that speak of several gods and their interactions with them. Yet the theory is that the people were mistaking extraterrestrials as gods. I'm putting my own spin on it where I believe that the big three represented in most mythologies actually represented three different alien races or extraterrestrial groups.
The bulk of the contact would have been with the extraterrestrials that they gave the strongest attributes to. The Greeks had Zeus and the Romans had Jupiter. Thor was in Norse mythology and Indra was in Hindu mythology. The Aztecs had Xolotl, the Mayans had Chaac and the Incans had Apocatequil. Set was in Egypt, Lei Gong was in China and Susanoo was in Japan. The world over civilizations had contact. They were mainly based in space but their ships were known to land on the planet and there were several stories of interactions with the gods or aliens. They were supposed to have been similar in appearance to the people of Earth.
There was a second alien race which set up camp in the oceans. The Greeks had Poseidon and the Romans had Neptune. Aegir was in Norse mythology and Varuna was in Hindu mythology. The Aztecs had Tialoc, the Mayans had Chac and the Incans had Pariacaca. Yam was in Egypt, Gong Gong was in China and Suijin was in Japan. Their main colony was Atlantis which may have been an island or a large ship. I believe these were more like the traditional grays. There are still reports in recent years of mermaids in the north Atlantic that share characteristics to the grays but have fish tails instead of legs.
The third group of extraterrestrials hail from another dimension rather than another planet. These are those represented by the underworld. The Greeks had Hades and the Romans had Pluto. Odin was in Norse mythology and Yama was in Hindu mythology. The Aztecs had Mictlantecuhtli, the Mayans had Hunhau and the Incans had Supayacetus. Anubis was in Egypt, Yama was also in China and Shinigami was in Japan. These aliens are able to travel between our dimension and theirs. At times they take people from our world into theirs. Sometimes those people get lost in the barrier between the two dimensions and they are perceived by those on our side as ghosts.
