The "theory" than man has an ancestral relationship with apes does not make any predictions. It is merely an assumption based on similarities in the present record. As such it does not qualify as science in the strict sense, but as speculation based upon unobserved, unrecorded phenomena. To the extent such theories exceed the bounds of the observable and the testable they hold no more intellectual credibility than the proposition that all things were created by an almighty God and are currently sustained by the same.
The idea that man has an ancestral relationship with apes is a part of a much larger and more inclusive theory that does make testable predictions and is falsifiable. If we were to find an organism with silicon oxides as its genetic material, I would be the first one to say that evolution must be wrong. If you found a large mammalian fossil in a precambrian rock layer, I would similarly conclude that the theory of evolution is wrong. Your example is only one prediction of the theory of evolution. Admittedly it is one that has not been fully tested, but every prediction of evolution that holds true lends increasing weight to the predictions of evolution that haven't been tested. I am not a biologist, so I am unable to provide more predictions of evolution, but they are present in the theory. Now tell me, what predictions are made by creationism? What observation would lead you to conclude that creationism is false? If you can't provide at least one observation that would cause you to stop believing in your idea of creationism, then it is not science. (Not necessarily implying that it isn't true, however.)