It is well-known that in science, alternative hypotheses often happen to be in competition, but the point here is that a scientific hypothesis often cannot be tested in isolation but must be tested relative to other hypotheses. The fact that P(complex structures|Darwinian evolution) is extremely small does not tell us anything about Darwinian evolutionary theory. It does not make evolutionary theory implausible … science education needs to explain to students why an event being extremely improbable, given the mechanisms postulated by a scientific theory, does not undermine this theory in any way.
In other words, we can construct a silly theory—such as that all of biology, and everything else for that matter, arose on its own—and so long as there are no competing theories then it is a fact. This is another example of how evolution has corrupted our thinking.