Don Juan had defined the concept of warrior-travelers, saying that it referred to sorcerers who, by being warriors, traveled in the dark sea of awareness. He had added that human beings were travelers of the dark sea of awareness, and that this Earth was but a station on their journey; for extraneous reasons, which he didn’t care to divulge at the time, the travelers had interrupted their voyage. He said that human beings were caught in a sort of eddy, a current that went in circles, giving them the impression of moving while they were, in essence, stationary. He maintained that sorcerers were the only opponents of whatever force kept human beings prisoners, and that by means of their discipline sorcerers broke loose from its grip and continued their journey of awareness. ~ Carlos Castaneda, The Active Side of Infinity
I believe that I read a similar interpretation of this in a book I read by Ken Carey, maybe in The Third Millennium: Living in the Posthistoric World. Carey, who had an apparent connection to the works of Castaneda which is evident in his writing, said something about how the Earth was a travel destination for universal beings, a place where they stopped to refuel, refresh and explore and that one day, a predatory race came to earth, never left and took over. If this is true then it may well explain the alien petroglyphs that have been found carved in stone around the world. Perhaps this was their “I was here” mark, much like people carve their initials in trees. Or maybe, they were depictions carved based on what those who inhabited earth at that time saw. Or both.