From the 1992 lecture brochure:
Humans are distinct from all other animals in two important respects. First, we are chiral, i.e. handed. We consistently use one hand in preference to the other for skilled tasks such as writing. Second, we communicate with structured language as opposed to the small repertoire of specific sounds used by whales or apes.
These capabilities are controlled by the brain which is itself chiral, speech being controlled by the left hemisphere in a way which is more specific for right handers than for left handers.
Overall, we are much less symmetrical than we appear superficially. The mirror image of one side of our bodies is often quite different from the other. The finger prints from the left hand are different from those on the right and below the surface our hearts lie on one side of the centre line and our livers on the other. One of our eyes and one of our ears is dominant in relevant tasks and we fold our arms and hands in a consistently asymmetric fashion.
We ask whether our handedness which is of long standing - at least half a million years - is innate or acquired. Evidence suggests that handedness is inherited in a complex way and there is no evidence to suggest an adaptive advantage. The mechanisms of inheritance (genetics) depend upon handed molecules and we return to this theme in Lecture 5. Meanwhile our perceptions of left versus right are crucial and the actions of our hands - in which we have clear superiority over other animals - are related to our mental processes including language.