Final answer:
The feeding system differences between hominins and monkeys lie in their diets and physical adaptations, with hominins exhibiting traits for omnivorous diets and tool use, while having smaller teeth and an upright, bipedal posture, and monkeys typically being less varied in diet and more arboreal.
Step-by-step explanation:
The feeding system of hominins compared to monkeys reflects differences in diet, anatomy, and evolutionary adaptations. Early hominins and human ancestors were omnivorous, consuming both plant and animal foods, and they had adaptations for a gathering-hunting lifestyle that persisted for the vast majority of their evolutionary history. They possessed characteristics such as small front teeth (canines and incisors) and very large molars, a fully upright posture resulting in bipedalism, shortening of the arms relative to the legs, increased dexterity of the hands, an increase in brain size, especially in the frontal lobes, and a decrease in bone mass of the skull and face. These adaptations were in response to environmental pressures and the quest for varied food sources.
By contrast, modern humans have a more diverse diet including a large amount of highly processed, low fiber foods, grains, and vertebrate meat, which has influenced the size of human teeth and jaws. Meanwhile, most primate species are omnivorous with a preference for fruit, except for humans, who consume a wider range and a more processed selection of foods. Gorillas and orangutans, which share our hominid lineage, typically exhibit quadrupedal movement, but they can walk bipedally when necessary. The evolution of tool use, as seen in homo habilis and homo rudolfensis, is also a significant distinction, contributing to dietary expansion and cultural advancement in hominins.