The identification and the evaluation of arguments are fundamental elements of critical thinking. However, the explicit promotion of these elements is virtually absent from university science courses. Much of the reason for this is that in most universities, across nearly all disciplines, instructors are required to see the conceptual content coverage of the syllabus as a priority. Moreover, lack of preparation and the fact that critical thinking activities are time-consuming rapidly reduce the interest of many instructors to include them in their courses. Here, we describe the use of a dialogue-based critical thinking classroom scenario (CTCS). The study used a mixed-methods approach with both quantitative and qualitative analyses of questionnaire responses. One hundred and seventeen undergraduates (73 females; 44 males; ages 16-24 years), enrolled in an introductory science course in Colombia, were asked to identify and evaluate arguments regarding a dialogue between two scientists who explore the controversial question of whether or not the concept of race is applicable to humans. It was found that the dialogue-based CTCS provided students with opportunities to identify and evaluate arguments both for and against the question and to make informed decisions about whether or not the concept of race in humans is biologically meaningful. Moreover, analyses of responses to closed-ended and open-ended questions revealed that more than half the participants were able to evaluate arguments in a fair-minded way. Practical implications for the cultivation of critical thinking skills in higher education and further research are discussed.