In debates over evolution and creationism, it is common for creationists' to demand for "proof" of evolution (common descent). Science doesn't deal in absolute proofs, though. Scientific theories
are provisional and are supported by evidence or data. Proof in science is not the same as proof in mathematics; in science, proof is gradually achieved through the accumulation of evidence which is best explained by one idea or set of ideas. This is what we have with evolution.
The direct evidence for common descent and evolution are enabling evidences. They demonstrate that common descent is possible and maybe even likely. However, they don't conclusively show that common descent occurred because no one was actually there to observe it over such a long period of time (the same problem that exists when there is no direct eyewitness in a murder trial
Inferential evidence for evolution is evidence that does not involve direct observation of evolution but from which we can infer that evolution has occurred. The three main kinds of inferential evidence for common descent are contemporary homologies, biogeography, and the fossil record. Inferential evidence is open to interpretation, but this doesn’t mean inferential evidence is weak. The more such evidence that exists and the less any alternatives can explain it all, the stronger evolution is.
Theodosius Dobzhansky, one of the 20th century's most eminent evolutionary biologists, had it right when he said, "Nothing in biology makes sense except in light of evolution." Evolution is the conceptual paradigm that ties together all the life sciences. Without the explanatory framework provided by the theory of evolution, the biological sciences would be disjointed and much within biology would not make sense. Denial of evolution thus amounts to denial of the foundations of modern biology.
Creationism is wrong — not simply mistaken or misunderstood, but flat-out and unequivocally wrong. It's a denial of the reality of our world in order to make room for a discredited religious ideology that has no connection with reality. Creationists disagree, of course, but do they realize just how large their task is if they wish to demonstrate that evolution is wrong? I don’t think so.
Is there evidence that supports the "theory" of (fundamentalist) creationism? Because creation theory in general does not have specified boundaries, just about anything could be considered "evidence" for or against it. A legitimate scientific theory must make specific, testable predictions and be falsifiable in specific, predictable ways. Evolution fulfills both of these conditions and many more, but creationists are unable or unwilling to make their theory fulfill them.