We can no more "prove" the theory of evolution than we can "prove" the theory of gravity. Because scientific theories can never be proven - they can only ever be useful. That is to say, the validity of a scientific theory is in its exploratory and predictive abilities. Not it's "proofs".
However, specific inferences from a theory can be factual (demonstrable with measurable accuracy). For example, it is a fact that objects with mass attract to each other. It's also a fact that we share a common ancestor with all other species on this planet.