Synkinesia may have played a pivotal role in transforming an earlier gestural language (or protolanguage, if you prefer) of the hands into spoken language. We know that emotional growls and shrieks in primates arise mainly in the right hemisphere, especially from a part of the limbic system (the emotional core of the brain) called the anterior cingulate. If a manual gesture were being echoed by orofacial movements while the creature was simultaneously making emotional utterances, the net result would be what we call words. In short, ancient hominins had a built-in, preexisting mechanism for spontaneously translating gestures into words. This makes it easier to see how a primitive gestural language could have evolved into speech—an idea that many classical psycholinguists find unappealing.
As a concrete example, consider the phrase “come hither.” Notice that you gesture this idea by holding your palm up and flexing your fingers toward yourself as if to touch the lower part of the palm. Amazingly, your tongue makes a very similar movement as it curls back to touch the palate to utter “hither” or “here”—examples of synkinesia. “Go” involves pouting the lips outward, whereas “come” involves drawing the lips together inward. (In the Indian Dravidian language Tamil—unrelated to English—the word for go is “po”).
Obviously, whatever the original language was back in the Stone Age, it has since been embellished and transformed countless times beyond reckoning, so that today we have languages as diverse as English, Japanese, !Kung, and Cherokee. Language, after all, evolves with incredible rapidity; sometimes just two hundred years is enough to alter a language to the point where a young speaker would be barely able to communicate with her great-great-grandmother. By this token, once the juggernaut of full linguistic competence arose in the human mind and culture, the original synkinetic correspondences were probably lost or blended beyond recognition. But in my account, synkinesia sowed the initial seeds of lexicon, helping to form the original vocabulary base on which subsequent linguistic elaboration was built.
Synkinesia and other allied attributes, such as mimicry of other people’s movements and extraction of commonalities between vision and hearing (
We also need to ask how gesturing evolved in the first place.2 At least for verbs like “come” or “go,” it may have emerged through the ritualization of movements that were once used for performing those actions. For instance, you may actually pull someone toward you by flexing your fingers and elbow toward you while grabbing the person. So the movement itself (even if divorced from the actual physical object) became a means of communicating intent. The result is a gesture. You can see how the same argument applies to “push,” “eat,” “throw,” and other basic verbs. And once you have a vocabulary of gestures in place, it becomes easier for corresponding vocalizations to evolve, given the preexisting hardwired translation produced by synkinesia. (The ritualization and reading of gestures may, in turn, have involved mirror neurons, as alluded to in previous chapters.)
So we now have three types of map-to-map resonance going on in the early hominin brain: visual-auditory mapping (