Why is evolution the only doctrine? What does this even mean?
I don't believe in evolution dogmatically. Why do I have to believe in evolution? If the theory of evolution was disproved tomorrow I would believe based on the new evidence. It is not the theory itself that has convinced me it is the efficacy of the theory's predictive power and the evidence provided independent from a plethora of branches of science.
It is also completely besides the point to being an atheist. If the theory of evolution were proved wrong tomorrow that would do nothing to convince me that some god(s) exist. It is not necessary that I believe in evolution in order to reject claims which have not met their burden of proof. If I were somehow convinced that evolution were not taking place in real time or that evolution is not the best explanation available to explain the diversity of species we see on earth it would be one more thing I didn't believe it would not cause me to believe in something totally unrelated.
I'm most interested to know what you mean by provide an alternative to evolution also
An alternative for how one kind of life evolves into another? That is thankfully somewhat explainable though you might be better served seeking out geneticists and paleontologists if you are really interested in the subject. If you wanted to disprove the theory I would start there.
If however you are referring to an alternative theory of the origins of life then you certainly don't understand what the theory of evolution actually states as it is not a theory about the origins of life at all but only how simple organisms can evolve into more complex ones through imperfect gene replication and the (non)guiding force of natural pressures causing some adaptations to be more successful in a given environment. I do not know how or where life originated and neither do you. In fact "god(s) did it" isn't any kind of answer even if it turned out to be technically true.
PLEASE UNDERSTAND THE DIFFERENCE BETWEEN THE THEORY OF EVOLUTION AND ANY GIVEN HYPOTHESIS CONCERNING HOW ORGANIC LIFE ORIGINALLY CAME TO EXIST.