Well all science fiction aside, and all silly magic religious theory aside.
At least the thousands of crazy person's encounter's have been all described as aliens being humanoid biped things similar to us.
even with space's infinite time and possibility, its pretty unlikely that they could evolve like that and we evolve like this separately.
therefore; aliens came first (because they are advanced tech, so we can guess) and humans(us) were put here on earth by them as some sorta silly alien social or developmental experiment. or whatever reason. and visit every so often every few years to watch us. then make a proper invitation to space as we put ourselves in the space age.
at least it explains more then "because god did it" lol. or the bullstuff science fiction has kids thinking alien life should be like.
