Anwar said:
Possible both the Voth and the ancestors of humans were the result of the Progenitor seedings.
That I can agree with, there really is no reason why two or more intelligent species could have formed (The Xindi come to mind).
However, what I think happened was that the Voth had a level of technology maybe less than a hundred years above our current level. They most likely developed on a large island or small continent that was free of the major predators of the time (i.e. T-Rex, Allosaurus). But did have some predators in order to help spur evolution (family/tribal groups, using tools to hunt, or defend themselves from predators, language).
They then were able to tame their land and develop advanced technology. They most likely saw the dinosaurs maybe even studied them, but kept away knowing that these creatures were too large and too numerous to tame. Then again, they might have simply been very eco-friendly and left them be knowing that their homes were protected by ocean.
They saw the changes happening on Earth, increased volcanism, geological instability, which they might have figured to be survivable. That is until the asteroid was spotted. They predicted the time of its impact, and using every resource they had, they fled into space.
That further spurred technological advancement until they reached the state that Voyager saw them at.
Why wasn't any trace of them ever found? One explanation is that their home was at or near ground zero for the impact. Another is that their home could have been a volcanic island that exploded and took the remnants of their civilization with them. Or simply, after 65 million years of disrepair their civilization vanished through erosion, and reclamation.