Darwin's Finches Only Evolve Back and Forth

Peter and Rosemary Grant are professors of ecology and evolutionary biology at Princeton. In this month's edition of the journal Current Biology they co-author the article "Darwin's Finches." The famus finch beaks oscillate, over time, back and forth. We can thus raise the question: if they diverge only then to converge back to what they were before, is that really evolution? The Grant's article leaves that question unasked and unanswered. Arn.org responds that we know the answer to the question is "yes," but it is only microevolution.