Figure 3. The use of prosody to signal levels of distress.

In accordance with the model, early Hominans became capable of modifying their contact calls with intonations (prosody). This modification could have originated for the purpose of expressing different levels of distress. In this figure, we see a Homo habilis child using prosody to modify the contact call to express a high level of distress ( A) or a low level of distress ( C). The child’s mother then registers the call (by integrating his prosodic intonation and voice, location, and the absence of his face) to recognize whether her child requires immediate ( B) or non-immediate ( D) attention.