Primate Physiology’s Legacy in our Human Experience
MASTERY OF SPACE(VOLUME)
Whereas Mammals mastered the two-dimensional horizontal plane, Primates extended their reach into the third dimension. This initially involved modifying their forelimbs for climbing – to pull themselves up into otherwise inaccessible reaches of the forest. As they liberated their forelimbs from the demanding task of holding up the weight of the body they were able to explore other ways to use these limbs, which evolved into tool use and bipedal gait.
Action in the three spatial dimensions can be seen in the anatomy of the shoulder.
The Homunculus is a model of how we would appear if our structure reflected the density of neurons invested for its control. The absolute dominance of the hands, and to a lesser degree the face and tongue, indicate the importance of tool use for our species. The thing I would change about the Homunculus is that he/she should be wearing a watch.
The evolution of the neurological framework that enabled bipedal gait and tool use is discussed here:
COGNITION AND THE EVOLVING BRAIN
NEXT EVOLUTIONARY LEAP
HUMAN EVOLUTIONARY POSSIBILITIES