Evolution is not a theory.
Evolution is “descent with modification”; it is an observable fact.
Darwin did not “invent” the concept of evolution, it has been present in both Western and Eastern thought for at least 2500 years.
The primary alternative to belief in evolution prior to its establishment as a fact was Essentialism (or “Special Creation”) – the belief that all organisms contain an immutable “essence” granted them by a creator.
A classic example of observable evolution in a biological system is the phenomenon of multi-drug resistant bacteria (“super bugs”) such as Staphylococcus aureus (golden staph).
Another example of observable evolution in a biological system is selective breeding – evolution driven by artificial selection.
Facts and theories differ in science in that the latter are explanations for the former.
Darwin and Wallace’s “Theory of Natural Selection” explains the fact of evolution by elucidating a mechanism for evolutionary change in biological systems.
Jean-Baptiste Lamarck proposed an alternative theory as an explanation for the fact of evolution; it was published in 1809 – 50 years before Darwin’s “On The Origin of Species”.
One way of testing the accuracy of a theory is by comparing its predictions to observable facts. Almost every observable fact from palaeontology, physiology, embryology, biochemistry and genetics matches up with the Theory of Natural Selection; those that do not are explainable as different forms of evolution (e.g., “genetic drift”).
The fact of evolution and the robustness of the Theory of Natural Selection do not disprove the existence of a creator; they just render it unnecessary.
Evolution is not unique to biological systems – it also occurs in language, culture and all anthropogenic technologies.