Care to tell me why it matters whether or not the collection of concepts within the theoretical framework of evolution can be conveniently reduced to a single sentence? It is not particularly difficult to discover the actual concepts at issue, e.g., variation through random mutation, changes in allele frequencies in a population over time, genetic drift, and natural selection.
It is particularly difficult to put those concepts on a postcard.
But why is that exercise even necessary? What point is served?
Take a few sentences. But state it, for goodness sake. You talk about - the theory of evolution. Can't you even say what it is? specifically, succinctly, as if you knew what you were talking about?