Misconceptions about adaptation by natural selection are widespread among adults and likely stem, in part, from cognitive biases and intuitive theories observable in early childhood. Current educational guidelines that recommend delaying comprehensive instruction on the topic of adaptation until adolescence therefore raise concerns because children's scientifically inaccurate theories about species may be left unchallenged for many years, allowing them to entrench and become difficult to overcome. In consequence, this investigation sought to explore whether classrooms of kindergartners and second graders could acquire a basic but comprehensive understanding of adaptation from an intervention constructed around two picture storybooks that mechanistically explain natural selection. Learning was assessed in near and far transfer contexts both immediately and a month later. Kindergartners and second graders demonstrated substantial learning of biological information; however, second graders showed pronounced abilities to near and far generalize, immediately and over time. Results suggest that causally cohesive interventions with an emphasis on mechanistic explanation facilitate children's classroom learning of complex counterintuitive scientific ideas. © 2017 Wiley Periodicals, Inc. J Res Sci Teach 9999:XX–XX, 2017.