Source: Arizona State University
The face you see in the mirror is the result of millions of years of evolution and reflects the most distinctive features that we use to identify and recognize each other, molded by our need to eat, breath, see, and communicate.
After our ancestors stood on two legs and began to walk upright, at least 4.5 million years ago, the skeletal framework of a bipedal creature was pretty well formed.
Limbs and digits became longer or shorter, but the functional architecture of bipedal locomotion had developed.
But the skull and teeth provide a rich library of changes that we can track over time, describing the history of evolution of our species.
Diet has played a large role in explaining evolutionary changes in facial shape
As the environment changed to drier, less wooded conditions, especially in the last two million years, early Homo species began to routinely use tools to break down foods or cut meat.
Changes in the human face may not be due only to purely mechanical factors
The human face, after all, plays an important role in social interaction, emotion, and communication.
Some of these changes may be driven, in part, by social context. Large, protruding brow ridges are typical of some extinct species of our own genus, Homo, like Homo erectus and the Neanderthals.