No scientific Theory can be proved - it can only be disproved. That is in the nature of science: a Theory is simply a Hypothesis that has satisfied many tests and defeated may attempts at disproof. However, a theory can be tested - and frequently is. The theory could very easily be *disproved* - by finding human bones in the same strata as dinosaur bones, for example. Or any other mixture of remains from what are regarded as widely differing times. You can also see evolution in action - for example, in the development of antibiotic resistance in bacteria. The large the species you want to see evolution in, the longer it will take, because it seems to take a few hundred generations for evolution to show up clearly. In bacteria, that may be only months; in mammals that is usually the better part of a century.