There are two types of evolution
Microevolution is the basic concept of natural selection, where the fittest survive and pass along their traits to their offspring. This is confirmed to be true, and people have witnessed it directly.
Macroevolution on the other hand is the idea that all living things come from a common ancestor, and over the course of billions of years every variety of creature we know descended from that one ancestor. This is not only not proven, it's full of holes. We have never seen one species transition to another over the course of generations, even in terms of creatures with shorter lifespans, like bugs. The "fossils" we've found of Neanderthals and other human ancestors are either speculation based on tiny bone fragments, or were proven to be hoaxes later on.