Why do some monkeys spend time grooming each other in large groups, while others lose their minds with rage if another monkey comes too close? Complex organisms exhibit behaviors that both fascinate and confound, and the way an animal behaves dictates how it interacts with its environment, with profound consequences. Individual behaviors can have dramatic effects on individual fitness, an individual's groupmates, and even the evolution of species. This leads to a fundamental question in behavioral evolution: why do animals do the things they do? The answer lies in the interaction between individual experiences and eons of natural selection. In this seminar, students investigate what organisms were, what they have become, and why. With a focus on the transitions in behavior that caused single cells to evolve over time into complex societies, students will apply evolutionary principles to individual development and explore how and why individuals choose certain behaviors over others.