Early Evolution of Bird-Type Language without Grammar: Duplication and   Mutation
  Using a series of computer simulations we have demonstrated a scenario of the early evolution of the bird-type primitive language. We do not assume wise agents who can use a grammar and manage an evolution without a grammar. Duplication and mutation of phrases is our strategy. Such a strategy is seen in wide classes of living phenomena. 
Miki Fukunoue, Osamu Narikiyo
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