Mutation and epigenetic molecular clocks in cancer.

A quandary of evolution is how to measure change over time. A natural inclination is to use morphologic criteria-the greater the differences between two phenotypes, the greater amount of time needed to evolve these differences. However, appearances may be deceiving, and another approach to infer time is with molecular clocks. Here, the greater the differences between two genomes, on average the greater the time since a common ancestor. Recent advances in DNA sequencing shed new light on how human cancers might evolve.