Some philosophers, known as statisticalists, claim that the concept of natural selection, as it is normally presented in population genetics, is statistical in character and cannot be construed in causal terms. On the contrary, other philosophers, known as causalists, argue against the statistical view and reaffirm the causal interpretation of natural selection. A key element in this debate is the dispute on the nature of drift. If drift is a cause of evolution, uncertainty in population genetics is due to some processes that make a population deviate from predicted outcomes. While causalists see drift as a distinct phenomenon originated by some set of natural processes, statisticalists claim that there is no process that accounts for this uncertainty, since the uncertainty lies not in the events but in the fact that natural selection in population genetics is modeled by a statistical theory. This article aims to illustrate the debate between causalists and statisticalists in order to present a challenge that statisticalists need to address if they wish to maintain a naturalist stance.