Answer to Question #122854 in Evolution for NIBEDITA RUDRA

Question

Describe the two non - language skills that seem to have played a significant role in the evolution
of communication abilities of humans.

Answer 1

1)     GESTURES

A study done across 3 European zoos found that shows the apes have at least 25 signals or gestures for ‘I want to play’, for example – ranging from a back roll and somersault, to a yank of their hair or a bite of the air, or clowning gestures like playing with their faces and placing objects on their heads. Brushing with a hand means they want something to stop, while embracing and pulling another ape at the same time means they want it to walk with them. These are very similar habitual or gestural acts that are done by the modern human as well.It seems not too far-fetched to suppose that the cerebral asymmetry of function developed in conjunction with the asymmetric activity of the two limbs during tool use, with the left hemisphere becoming the hemisphere specialized for sequential limb positioning/ movement (precise motor control). Thus when a gestural system was employed, it would presumably also be controlled primarily from the left hemisphere. It is clear that the employment of most tools requires the asymmetrical use of both arms, in modern man context, it is systematic where one hand (usually the left) acts as the stable balancing hand, and the other (right) acts as the moving hand for actions like chopping or hitting.

Researchers have also found out that neurons in the premotor cortex of the primate respond when it makes grasping movements or gestures with their arms or hands. Also dubbed as “mirror neurons”, they also respond when the animal observes another animal making movements, thus mapping the perceived gestures into produced gestures. This also brings us to understand the manipulative nature of primates.

Modern humans

At first, facial and manual gestures would have been accompanied by grunts (no speech), but in modern humans vocal language is accompanied by manual gestures to add meaning/ support the message they want to convey. We often include manual gestures to substitute spoken particles/ words (i.e. He’s completely (gone crazy) – using a spiral twisting manual gesture near the head to indicate crazy).

                                2)  FACIAL EXPRESSIONS

It is likely that the face increasingly became more involved in gesturing, along with the higher sophistication of tools usage, creation and manipulation, which heavily occupied the hands. The development of facial muscles and thinner jaw structures also enabled for more flexibility in creating such expressions. Facial gestures can also be associated with vocalization acts and sounds like lips-smacking, teeth chattering and whistling (to display hunger, looking for fun).