While most students take a position for or against evolution, few actually understand the concept of natural selection or appreciate the idea of descent with modification. This problem/activity challenges students to provide structured arguments and evidence for their belief-based conclusions on either side of the creation-evolution issue. The “right answer” is insufficient without support. The problem focuses on characteristics of human ancestors (e.g.scales) rather than the ancestors themselves (e.g. fish or reptiles), requires students to use the library and/or Internet resources, and gives them practice with oral and written communication skills. It introduces PBL (ice-breaker) in a way that emphasizes both content and process.