2Words are the physicians of the mind diseased.-Aeschylus, Prometheus Bound
INTRODUCTIONThe question of the origin of modern humans has inspired more scenarios, stories, and research than perhaps any other in biology and the humanities. In one of the first such stories, Plato describes how Epimetheus the Titan distributed abilities to each kind of animal, but used them up before reaching humans. His brother Prometheus, seeing that humans had nothing enabling them to survive, stole technology and fire, and knowledge and philosophy, from the gods and bequeathed these skills and abilities upon them. As eating from the tree of knowledge prompted the Biblical God to banish Adam and Eve, so Zeus punished Prometheus by binding him to a rock, and so humans have paid dearly for their gifts of cognition ever since they were bestowed.In this paper I will seek to bring the Prometheus myth and metaphor up to date, with a focus on language, the gift most uniquely human. Analysis of the evolution of human language brings together three of the greatest unknowns in biology: the brain, the genome, and the evolution of modern humans. It has thus generated a vast literature, a verbiage so extensive that it tends to obscure the paucity of facts. Moreover, the facts that do exist reside in diverse, specialized disciplines from genetics to phylogeny, paleontology, anatomy, neuroscience, psychology, psychiatry and linguistics. My goal is to integrate across these disciplines using the only tool that unites them, evolutionary biology. Language, and humans, are social, so my conceptual monkey-wrench of choice for such a construction is theory for the evolution of social behavior (Alexander 1980(Alexander , 1987, the only science that addresses how human sociality, and its genetic underpinnings, change under Darwinian selection.I begin with a few basics about the brain, language, and how natural selection works at different levels from genes to groups. Next, I explain how the brain and language can be studied using the three main approaches for analyzing the adaptive significance of traits: functional design, measurement of selection, and the comparative method. I then apply the comparative method to a new form of diversity: autistic and psychotic-affective spectrum conditions, the main generalized 'mutations' of human sociality and language. Our goal here is to understand how human language and communication have evolved by analyzing how these adaptive systems can be perturbed. The nature of such perturbations provides insights into our cognitive and emotional architecture, 3 just as mutations in a single gene provide insight into its functions in physiology and development.Virtually all previous studies of language evolution have focused on cooperative and beneficial aspects of human communication, such as coordination of activities, pedagogy, or impressing a potential mate with syntactic and emotive prowess. This perspective is incomplete, because human social interaction is always permeated by complex mixtures of cooperation and confl...
