Which of the following is a result of the evolutionary changes in hominins' faces?

The evolutionary changes in hominins' faces show a trend towards flatter faces, which is significant for several reasons. Over time, as hominins evolved, they shifted from a more prognathous face—characterized by a protruding jaw and forward-projecting teeth—to a flatter facial structure. This change is associated with a number of factors, including dietary adaptations, the development of tools, and changes in social behavior.

Flatter faces allow for a more vertical arrangement of the dentition, which is suited for a diet that includes a wider variety of foods, as opposed to the tougher foods that earlier ancestors might have consumed. Additionally, a flatter face can indicate a reduction in the size of the jaw muscles and teeth, possibly due to cooking and the use of tools, which reduce the need for heavy chewing. This evolutionary trait also supports changes in brain size and structure, as a flatter facial structure is often associated with larger brain capacities, allowing for advanced cognitive functions, communication, and social interaction.

In summary, the trend towards flatter faces in hominins reflects significant changes in behavior, diet, social structures, and cognitive development throughout human evolution.