Using colorectal cancer (CRC) as a model, we review some of the insights into cancer evolution afforded by cancer sequencing. These include: non-linear and neutral evolution; polyclonality of driver mutations and parallel evolution in adenomas, although only rarely in carcinomas; the ability of mutational processes to shape evolution against the force of selection; the presence of rare driver genes that function in the same signalling pathways as the longstanding canonical drivers; and the existence of selective windows that constrain the functional effects of cancer driver mutations within limits.