Excellent question, Nothingness. What do you predict?
Let me make a prediction based on evolution.
Just from Linnean taxonomy, humans are very similar to apes. So we should find fossils that are intermediate between ape and humans.
Now here is the observation.
Consider
Australopithecus afarensis. It is the size of a chimpanzee. It is obvious an ape-like fossil. It had a brain about the size of a chimpanazee. It had locking wrist bones, which helps a chimp knuckle walk. But in relation to its size, its arms were intermediate in length between chimp and human -- if it were a knuckle walker, it would be very uncomfortable one. But it wasn't a knuckle walker -- the pelvis and the feet indicate that it was bipedal - a human trait. It had long canines like extant apes, but otherwise the shape of the jaw and teeth were intermediate between humans and chimps.
Let me make another prediction.
There should be fossils that bridge the gap between
A. afarensis and modern humans, both in morphology and time.
Observation: Now we have
Homo erectus. It is definitely bipedal, with no traces of knuckle walking or arboreal behavior that
A. afarensis had. It was more robust. The cranium was much larger, even approaching the very low end of range of modern humans. The face and teeth were much more human like. Yet it wasn't human -- even I can look at a skull and tell that. And it wasn't an ape (except in the sense that all of us tailless primates are apes -- you know what I mean) -- even I can look at the skull and tell that. In fact, creationist scientists themselves debate whether
H. erectus is human or ape. Best of all, it was dated, by means from other fields of science that have nothing to do with evolution, to be intermediate in age between
A. afarensis and modern humans.
Now, based on your hypothesis of a common designer, what do you predict? And how are your predictions sufficiently different from that of the theory of evolution to distinguish them?
Now, according to the theory of evolution, there was a common ancestor to chimpanzees and
A. afaranesis. If and when we find such fossils that show intermediate characteristics between
A. afarensis and chimpanzees, and if and when it is dated older than
A. afarensis this will be another confirmation of evolution.
But does your theory of a common designer predict such fossils will be found? If so, why? If not, then what does it predict? That is how one tests a scientific theory.