We are the descendents of anther world, but of this world at the same time. Thousands of years ago, an advanced race of beings, who being highly intelligent, and benevolent at the same time, rather then destroy a highly flawed race of creatures they called humans, decided to rid themselves of this contaminated species, by sending them to a sort of penal colony. Rather than exterminate the humans they decided to find a planet (Earth) that would support this species, and let nature take it’s course.
They thought it possible the species could advance to a point of not destroying everything they touch. There’s ample evidence that alien space craft are real, are here now, and historical records would indicated they have been here for thousands of years. The Human species (us) of aliens are a violent, unpredictable race, that raises havoc with everything they touch. Last century alone, we managed to kill 180 million of ourselves, mostly by the hands of governments created by the human (us) species. Humans lie, cheat, and steal in their natural state, but above all we kill, we are never satisfied, always wanting power, and control over everything, and once achieved, total discontent follows, and the cycle repeats.