This introduction presents an overview of key concepts discussed in the book. The book addresses central issues in the domain of language development: the range of evidence in favor of a language instinct, the existence of a critical period for language acquisition, the issue of maturation in the context of language acquisition, and the impact of language on other cognitive systems. It focuses on the interplay between mind, brain, and behavior. The book deals with the nature of theoretically informed experiments, working memory and language processing, modularity, language deficits, and pathologies. It focuses on a range of issues relevant to the study of language evolution: the cognitive capacities of non-human primates, the abilities of non-human vocal learners, the potential use of fossil records to shed light on the evolution of language, the possible role of natural selection, and the insights from computational modeling in the context of language evolution.