Book excerpt: Principles of Evolution considers evolution in the context of systems biology, a contemporary approach for handling biological complexity. Evolution needs this systems perspective for three reasons. First, most activity in living organisms is driven by complex networks of proteins and this has direct implications, particularly for understanding evo-devo and for seeing how variation is initiated. Second, it provides the natural language for discussing phylogenetic trees. Third, evolutionary change involves events at levels ranging from the genome to the ecosystem and systems biology provides a context for integrating material of this complexity. Understanding evolution means, on the one hand, describing the history of life and, on the other, making sense of the principles that drove that history. The solution adopted here is to make the science of evolution the primary focus of the book and place the various parts of the history of life in the context of the research that unpicks it. This means that the history is widely distributed across the text. This concise textbook assumes that the reader has a fair amount of biological knowledge and gives equal weight to all the major themes of evolution: the fossil record, phylogenetics, evodevo, and speciation. Principles of Evolution will therefore be an interesting and thought-provoking read for honors-level undergraduates, and graduates working in the biological sciences.