Humans brought to Earth, not native to it.
Diogenesister, you might be thinking of Blackwolf instead.
That poster seems to be a teenage girl.
I'm hope yet doubt that the true answers can happen in our lifetime.
Maybe Dr. Who could help you.
You could pop into the Tardis, go back in time and see for yourself.
This type of stunted thinking is used to explain other things but all they do is make for a crazy complex scenario instead of the bleeding obvious one.
For instance, some people claim that it's impossible that humans could discover or figure out how to make fire. The explanation they come up with is that it must have been brought to earth by space aliens who passed it onto people (who seem to pick it up enough to pass it on to others).
I think in their heads this "solves" the issue of fire-making being discovered but it doesn't - it just now has to be discovered on another planet by other creatures with different materials (seems like they must have wooden trees just like ours - that's handy!) and of course there's now interstellar space travel that needs to be invented and applied.
All to avoid accepting that some smart dude figured out how to make fire and our ability to communicate and pass on knowledge means that we benefit as a species, building up a body of knowledge and know-how over time.
Same with life / evolution - instead of accepting the overwhelming evidence that life developed to suite the planet *on* the planet, people want to come up with some kooky explanation involving spaceships and live being developed on some magical mirror-earth where it ends up exactly suited for this one ... somehow.
It's just utter drivel.
Occam's razor is the tool needed. Why look to aliens to explain what is already explained by palaeontology?
This is the plot of at least two recent movies. Also, I think every Star Trek series that has ever been made has had an episode dedicated to this idea. Heck, I think ST the Next Generation had two!