This case study was developed for an upper-level undergraduate evolution course in order to provide an example of natural selection in hominids and encourage critical thinking and understanding of the subject. The case focuses on the cognitive evolution of great apes in response to diet specialization. Orangutans, along with other great apes, are in decline globally due to habitat loss and changing environments. Because of great ape life history traits, their high cognitive function, and diets that specialize on ephemeral fruits, they are faced with a situation where they may not be able to adapt to rapidly changing environments. This may lead to a “cognitive trap” whereby their high cognitive functioning may ultimately help lead to their extinction. The case provides an overview of how natural selection shapes adaptations in great apes, such as dentition morphology, in response to diet. Finally, the case provides a review of natural selection and its requirements, how selection can lead to adaptations, and how some traits may even become maladaptive when environmental conditions vary.