Innateness and maturation in linguistic development

Language is species-specific, species-wide, and highly structured. Its principles (Universal Grammar) are innate (genetically determined) in the child, although some linguistic capacity is subject to a maturational schedule, examples of which are given. Some particular aspects of language are learned, in a way driven by Universal Grammar. However, empiricist "learning theories" of all types are far too weak to be useful in explaining either the final adult language or the precise timing of developmental processes. The assumption of Universal Grammar is, in fact, crucial in explaining what kind of learning actually takes place.