Let's make this easy; here's some links to Wikipedia articles:
Historical Linguistics - includs the study of language origins and tracing the historical relations between languages.
Creole languages - languages that are created naturally by next generation learners of cultures working with pidgins; pidgins are communication systems developed between adult populations who do not share a common language
Nicaraguan Sign Language - a sign language that developed in isolation among a deaf community of children.
Maybe that helps get you started...
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