Hypothetically, if humans came from somewhere else (or were put here), they might indeed have started at a much higher tech level than they ended up at, regressing quickly as they had to make their way on a new world with what was available (and knowledge of the advanced past quickly fading).
Wouldn't surprise me at all if both Venus and Mars had all kinds of life on them before Earth did, and as both fell apart, Earth became the new prime real estate to flee to.
I'm getting into some wild speculation now though.