In nature, competition within and between species is the norm, yet nature is also reputed to be a "peaceable kingdom" where animals cooperate rather than compete. This study explored how such contrasting views of nature influence students' biological reasoning. College undergraduates (n = 165) assessed the prevalence of cooperative behaviors, such as food sharing and symbiotic cleaning, and competitive behaviors, such as cannibalism and parasitism, and these assessments were compared to their understanding of evolution as a process of differential survival and reproduction. Participants underestimated the prevalence of competitive behaviors relative to cooperative ones, particularly for behaviors directed toward other members of the same species, and the accuracy of their judgments predicted how well they understood evolution, even when controlling for other predictors of evolution understanding, including perceptions of within-species variation and perceptions of geologic time. These findings suggest that overly benevolent views of nature compete with more realistic views and may hamper our appreciation of the mechanisms of adaptation.