Educational efforts to incorporate ethical decision-making in science classrooms about current science and technology issues have met with great challenges. Some research suggests that the inherent complexity in both the subject matter content and the structure and dynamics of classrooms contribute to this challenge. This study seeks to investigate the viability of an educational heuristic based on a complex systems evolutionary approach to both harness complexity inherent in the learning system of the classroom and to improve student knowledge of a complex scientific issue. The evolutionary mechanisms of variation, interaction, and selection were used to construct a 10-day curriculum and instruction unit on the topic of genetic engineering. Eleven Grade 9 students participated in the study. The data analysis was completed using three data sources: daily database discussions and ratings and rationales provided over four time-points, probing student opinions and understanding of genetic engineering research. A repeated-measures analysis of variance conducted on 43 student rationales indicated a continuing trend of increasing understanding of complex systems concepts over time. There is also evidence to show that students as a whole group operated as a complex system in their patterns of decision-making. A number of themes identified in student database discussions reveal processes students themselves believed influenced change at the social and conceptual level, including the evolutionary mechanisms upon which the program was designed. (Contains 5 figures, 7 tables and 2 notes.) [Research for this article was partially funded by Imperial Oil Charitable Foundation.]