If we start thinking in terms of what happened through the stages of evolution, when mammals evolved they required lots of nurturing. When they were born, they were not able to take care of themselves. Unlike reptiles that hatch and scamper off to the water, mammals need to be suckled. So with this physiological evolution, there also evolved social cueing—facial expressivity, crying, vocalizations, sucking movements; all these types of behaviors of the neural regulation of the face provide poignant cues and are part of the mammal’s repertoire for behavioral and state regulation.
We still use the same “cueing” communication system to test social interactions. The neural regulation of the facial muscles provides a way to reduce psychological distance before we deal with the inherent risk of moving physically closer. This social engagement system enables people to touch each other. We don’t just walk up and touch someone; there’s a whole interaction between the face, vocalizations, other bodily cues, to see if we feel safe with each other. Then we can touch. Thus, social engagement behaviors precede the development of social bonds. Social engagement behaviors provide an option to test interactions in “psychological space” with very low risk, prior to the test in “physical” proximity. Polyvagal theory shows that as reptiles evolved into mammals, the neural regulation of the heart and lungs changed. It came to be regulated by an area of the brain that also controlled the facial muscles. After that, emotional expressivity, ingestion of food, listening and social interactions were all related to how we regulated our bodies. Those components calmed us down. Thus, social behavior could be used to calm people down and to support health, growth and restoration.