Final answer:
Primates are thought to have developed unique traits due to the adaptive pressures of arboreal living, visual predation, or coevolution with flowering plants. These adaptations include opposable digits for grasping, enhanced vision over smell, and tactile discrimination for feeding among the angiosperms.
Step-by-step explanation:
The theories on the adaptive significance of traits that characterize primates suggest different evolutionary pressures that shaped primate development. The arboreal theory suggests that primates evolved traits such as opposable thumbs and toes for better grasping in a tree-dwelling lifestyle. Additionally, this theory highlights enhanced vision over smell, which is pivotal for navigating the three-dimensional arboreal environment.
Another theory is the visual predation hypothesis, which argues that primate adaptations are the result of hunting insects and small animals in the forest undergrowth rather than living in the trees. Traits like forward-facing eyes and grasping extremities aided in the detection and capture of prey amidst the foliage.
The angiosperm theory posits that primate evolution is linked to the rise of flowering plants. This suggests that the ability to visually discriminate and tactfully handle fine food items like fruits and seeds from these plants was an adaptive benefit that shaped primate traits.