In primate evolution, what advantage did forward-facing eyes provide?

Forward-facing eyes in primates offer a significant advantage in terms of enhanced depth perception. This ocular arrangement allows for binocular vision, where both eyes can focus on the same object from slightly different angles. The brain combines these two images to create a single, three-dimensional view of the environment. This ability is crucial for activities that require precise judgment of distance, such as leaping between branches in a forest canopy or accurately reaching for food. Enhanced depth perception plays a vital role in a primate's ability to navigate their environment, find food, and avoid potential predators, all of which are essential for survival.

The other choices relate to different adaptations or features that do not directly stem from the positioning of the eyes. While improved smell pertains to olfactory capabilities, better balance is typically linked to anatomical features rather than vision, and stronger grasping abilities are related to the structure of hands and feet rather than the placement of the eyes. Therefore, forward-facing eyes specifically enhance depth perception, making it the correct answer in the context of primate evolution.