In any situation in which qualities may give rise to order which can both change and persist over time, evolution not only can occur but must occur. Consider the opening 'moments' of the universe. Potentially, every possible configuration of natural forces may have occurred. The vast majority of them, however, would be unstable and incapable of 'surviving' the ruthless 'selection' of the cosmic firmament. However, some configurations would persist longer than others; some would be capable of influencing the universe around them in such a way as to make conditions more congenial to the formation and propagation of configurations similar to their own. Eventually, the 'particles' and 'forces' we know today form and go on to combine into more complex structures. Interaction of these particles and forces vast time scales creates layer upon layer of complexity: atoms, molecules, quasars, stellar and planetary systems. Various structures compete for the resources created by the big bang, diversifying and forming an 'astrophysical ecosystem'. Hydrogen atoms come together to form stars; stars create heavy elements, which then form more quickly into hotter stars and the cool, solic planets which orbit them. Combinations of these complex conditions eventually lead to the formation of complicated molecules which can more quickly and consistently create copies of themselves in a way which leads to yet more intense competition for even scarcer resources: replicating organic chemistry. For billions of years, organic molecules slowly develop in complexity and begin to form stable systems that enhance the viability and replication of their component parts: organisms. Prokaryotes beget eukaryotes, which beget multicellular life, which begets plants and animals, which beget proto-humans, which beget self-replication mental information constructs: memes. At every stage, a slow buildup of complexity and diversity leads to a moment of transition in which an association of disparate parts yields a vast dividend in stability and replication power, all from the basic premise of variation, selection, replication: given any situation in which order can both change and persist over time, any structures which persist longer, and influence other structures in such a way as to assist the formation of order similar to themselves, will tend to create conditions of increasing diversity and complexity.
The more I consider it, the more I believe that the theory of evolution has far broader explanatory power than just the narrow case of biological life. Meme theory is the most obvious extension of evolution, but ultimately the case could be made for extending evolutionary theory into every aspect of order observable in the universe. This could be thought of as the General Theory of Evolution, of which Darwin's Special Theory of Evolution is a particular case.