Need to have the information for advanced course work in department. Need to know the normative information in this class for courses on pathologies. All known human cultures have a spoken language. Some do not have written language. Some use sign language as alternative.
Children develop language on about the same schedule, regardless of the language they are learning.
Prerequisites for language development a. Deaf will not develop speech without special intervention. Dependent on exposure to others in environment using language. We speak the language we hear as we grow up. A French king brought newborns from around the world to determine what language they would speak if they were not exposed to any language from birth.