I don't feel like that is a concern you should be just dismissing out of hand. They're remarkably similar to a race that was showcased in one of the single most popular sci-fi series ever to have existed. Going ahead, you need to keep that in mind, whether you knew about them beforehand or not.
But, to answer your question: I'm with Doshii on this one. Earth has always been kept distant, at a good remove from the rest of the setting. While several races can honestly be presumed to be descended from humans, none of them have ever claimed to come from Earth as an origin, and I think it should remain that way. Whether the premise of HOW they came to leave Earth is feasible or not, I don't think it SHOULD work. Earth is a lost, distant legend at most, and it should stay that way. I just don't see how them being from Earth in any way actually improves them as a race, instead of them just being a species who evolved in similar fashion to Earth's dinosaur's originally.