The Evo-Devo of Vocal Communication: Insights From Marmoset Monkeys

The vocal behavior of marmoset monkeys reveals that they exhibit developmental processes strikingly similar to early human vocal development. These processes include babblinglike vocal output and a role for social feedback in changing this output into mature-sounding vocalizations. We show how the rhythmicity of the autonomic nervous system may be part of the physiological mechanisms for how the early vocalizations are produced and how they are shaped by social feedback. We then propose that humans and marmosets may have converged on this similar vocal development trajectory because they both adopt a cooperative breeding strategy. While the similar behaviors are the result of convergent evolution (ie, Old World nonhuman primates do not exhibit them), the neural circuits underlying the behavior in marmoset monkeys and humans may be identical as mechanisms for neural development are highly constrained.