Final answer:
Eocene primates evolved to have larger brains, more developed vision with the ability to see in three dimensions, and a diminished sense of smell compared to Paleocene primates. Therefore, the correct option is A.
Step-by-step explanation:
Eocene primates differ from Paleocene primates in several key ways, notably their increased reliance on vision, a reduced sense of smell, and larger brain size. Compared to other mammals, primates evolved to have larger eyes with forward-facing placement, allowing for stereoscopic vision (three-dimensional vision) due to an overlap in the visual fields of both eyes. Their reliance on vision is further strengthened by an enlarged brain area associated with vision processing, and a reduced area for olfactory (smell) processing. The evolution of primates during the Eocene saw significant anatomical changes including larger brains, reduced snouts, and adaptations like postorbital bars that are indicative of their reliance on sight over smell in their environment. Essentially, Eocene primates developed larger brains, enhanced visual capabilities, and diminished olfactory faculties compared to their Paleocene ancestors.