The Evolution of Speech and Language
Human speech, language, and cognition derive from anatomy and neural mechanisms that have been shaped by the Darwinian process of natural selection acting on variation but that have roots present in other living species. Languagedid not suddenly arise 50,000-100,000 years ago through a mutation that yielded an innate "faculty of language " nordoes the human brain include an organ devoted to language and language alone. Broca's area is not the center oflanguage. Neural circuits linking local activity in different neural structures regulate complex behaviors. Neural circuits thatwere present in early mammal-like reptiles play a part in regulating laryngeal phonation, conveying both referentialinformation and emotion. Speech plays a central role, enabling transmission of information at a rate that exceeds theauditory fusion frequency. The unique human tongue enhances the robustness of speech, but Neanderthals and otherarchaic hominins whose neck and skull proportions preclude their having an adult-like human tongue nevertheless couldtalk. Comparative studies of present-day apes suggest that hominin "protolanguage" lacking syntax never existed. Theneural bases of human language are not domain-specific - in other words, they are not devoted to language alone.Mutations on the FOXP2 transcriptional gene shared by humans, Neanderthals, and at least one other archaic speciesenhanced synaptic plasticity in cortical-basal ganglia circuits that are implicated in motor behavior, cognitive flexibility,language, and associative learning. A selective sweep occurred about 200,000 years ago on a unique human version ofthis gene. Other transcriptional genes appear to be implicated in enhancing cortical-basal ganglia and other neuralcircuits.
