Suppose I wanted to write a novel, in which there was another planet the same size as Earth, and it shares Earth’s orbit. I will name the other planet, Tierra. No one on Earth ever saw Tierra because it was exactly halfway away from us in the orbit. Therefore, the sun was always between Earth and Tierra. Both planets were created at the same time, and life on them turns out to be similar. I want the people on Tierra to look like Earth people, but I want them to be eons ahead of us in science, technology, personal development, and social order. The UFO’s seen so often on earth are from Tierra, mostly citizens of Tierra visiting Earth on sightseeing trips.
If life evolved simultaneously on the two planets, how can I explain the far more advanced development of the people on Tierra? Suppose, too, that I wanted the relatively astronomic difference to be due to something the earthlings could have done early in their development, but didn’t.—something that could be seen as taking the wrong option in a fork in the road. Make it something we earthlings could possibly do now to start making the kind of advancement in our social order that we have made in science and technology.
I’ll leave it for you to ponder. I think I have a good idea, but if you have any suggestions, send them to email@example.com. I’ll post the best idea(s) soon.