Since at least 1930, evolutionary explanations have focused on Darwin's mechanism for driving evolution, namely natural selection (and one of its side effects, adaptation), mostly neglecting other evolutionary forces. Yet, genetic drift probably plays a huge role in plant evolution, as does drift's supporting cast of gene-gene interactions and inbreeding. I argue that cactus evolution should be largely driven by drift, rather than selection, because of high rates of polyploidy, inbreeding, and endemism, which collectively result in highly reduced effective population sizes for virtually all of the Cactaceae.