Dual neural network model of speech and language evolution: new insights on flexibility of vocal production systems and involvement of frontal cortex

Human speech vastly outperforms primate vocal behavior in scope and flexibility making the elucidation of speech evolution one of biology's biggest challenges. A proposed dual-network model including a volitional articulatory motor network originating in the prefrontal cortex that is capable of cognitively controlling vocal output of a phylogenetically conserved primary vocal motor network attempts to bridge this gap. By comparing neuronal networks in human and non-human brains, crucial biological preadaptations are found in monkeys for the emergence of a speech system in humans. This model can explain behavioral evidence for vocal flexibility in cognitive tasks as well as during vocal development in monkeys as intermediate steps in the continuous evolution of speech in the primate lineage.