There are two principal explanations for the differences in maxillary angle, teeth, and palate between chimpanzees and humans. The first is that although chimpanzees and humans can eat many similar foods, they do not have similar diets overall. Chimpanzees in the wild eat more fruit than anything else, with figs playing a particularly important role in their diet. They also eat nuts, seeds, and, when other food is scarce, even tree bark. Although chimpanzees can eat meat, this typically accounts for only about six percent of their diet. They also eat insects, many of which have hard shells.

The other vital difference between humans and chimpanzees is that chimpanzees do not cook their food. This means that when they do eat meat, the exercise is much more demanding for their teeth than when a human eats the same type of meat cooked. A great deal of the food eaten by human beings, including fast food such as hamburgers, fries, and ice cream, could be consumed fairly easily without any teeth at all and without much space inside the mouth for chewing. Chimpanzees require sharper teeth than humans do to process their diet, and they put more pressure on those teeth. They also need more space inside their mouths to chew tough food.