This interrupted case study leads students through an exploration of the evolutionary origin of apparently cooperative guarding behavior in meerkats. Students generate hypotheses, evaluate the predictions associated with them, and then analyze graphical data from the literature to determine which hypotheses for the evolution of this behavior are supported by evidence. Students are led to confront their misconceptions about altruism and solidify their understanding of how natural selection operates in animal groups to drive the evolution of specific behaviors. Before beginning the case, students should have a firm grasp of natural selection, fitness, and evolution, and should be able to write and identify good hypotheses and predictions. Originally designed for an introductory biology course for majors, the case could also be used in a non-majors course or an upper-level course, such as animal behavior or evolution, in which it would serve as the first in a series of lessons exploring the topics of kin selection, inclusive fitness, and eusociality.