Seeing as how the Last Common Ancestor between us and chimps is estimated to have existed somewhere between 7 million and 10 million years ago, it is rather unlikely there were super advanced people 300 million years ago. 300 million years ago would place them squarely in the late Carboniferous period. There weren't even dinosaurs at that time.

There is no such evidence in any time period. And while such a time scale as 300 mya, in the Carboniferous period, would limit our knowledge, we do have an ample fossil record: the animals that would become mammals don't appear until 50 million years later. It'd be another 200 million year until the primate opposable thumb developed.