4.03 - The Role of Vision in the Origin and Evolution of Primates

Abstract

The origin of Primates was associated with a suite of changes to not only the visual system, but other functional systems as well. Understanding the role of vision in primate origins and evolution requires an understanding of the integration of visual system function and evolution with these other systems. Changes to the visual system at primate origins resulted in increased sensitivity to low light levels, improved fine-grained stereopsis, increased visual acuity, and increased motion sensitivity. These changes to the visual system were accompanied by improved abilities to localize sounds or movements in space, increased manual dexterity, and changes to the somatosensory and somatic motor systems that provided for improved control of visually guided reaching and grasping movements, possibly for feeding in the terminal branches. These changes were accompanied by modifications in gait and musculoskeletal anatomy of the hands and feet related to arboreal locomotion, including leaping and grasping on fine-branch supports. These changes were manifest not only in the musculoskeletal periphery, but also throughout the central nervous system, including the origins and terminations of the corticospinal tracts, the premotor areas controlling limb movements, the visual cortex, and the primary and secondary sensorimotor areas. Explanations for primate origins must take into account not only the changes in these separate systems, but also their integration in the whole organism.