Final answer:
Primates' enhanced sense of touch is attributed to well-developed tactile pads on their fingers. Other adaptations such as opposable thumbs and brachiation also distinguish primates from other mammals, but it's the tactile pads that are crucial for the sense of touch.
Step-by-step explanation:
Primatologists have found that the evolutionary development responsible for primates' enhanced sense of touch is the presence of well-developed tactile pads on their fingers. These tactile pads are made up of fat and nerves, which enhance the sensitivity of touch. Such tactile sensitivity in primates is conducive to a variety of tasks in their arboreal or terrestrial environments. Contrary to options such as the lack of opposable thumbs and reduced tactile sensitivity, which would hinder touch sense, or increased reliance on smell, which is not primarily associated with the sense of touch, the well-developed pads play a crucial role in primates' tactile abilities.
In contrast to other mammals, primates exhibit several adaptations beneficial for life in the trees, such as the presence of five digits on each extremity, opposable thumbs and, in many species, opposable big toes that facilitate grasping and manipulating objects. Furthermore, primates' reduced reliance on the sense of smell and their adaptations for brachiation, like the rotating shoulder joint, and stereoscopic vision, are evolutionary developments that distinguish their sensorial experiences from those of other mammals.