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The face you see in the mirror is the result of millions of years of evolution and reflects the most distinctive characteristics that we use to identify and recognize ourselves, shaped by our need to eat, breathe, to see and communicate.
But how has the modern human face evolved to look like this? Eight of the leading experts on the evolution of the human face, including William Kimbel of Arizona State University, collaborated on an article published this week in the newspaper Nature Ecology & Evolution tell this story of four million years. Kimbel is the director of the Institute of Human Origins and Professor Virginia M. Ullman of Natural History and the Environment at School of Human Evolution and Social Change .
After our ancestors stood on two legs and started standing up at least 4.5 million years ago, the skeletal frame of a biped creature was rather well formed. The limbs and figures have become longer or shorter, but the functional architecture of the biped locomotion has developed.
But the skull and teeth provide a rich library of changes that we can follow over time, describing the evolutionary history of our species. The main factors in the changing structure of the face include brain growth and adaptations to respiratory and energy demands, but most importantly, changes in the jaw, teeth and face have responded to changes in diet and eating behavior. We are or have evolved to become what we eat – literally!
Diet played an important role in explaining evolutionary changes in facial shape. Early human ancestors ate difficult plants that required large jaw muscles and cheeks to decompose, and their faces were therefore wide and deep, with massive muscle attachment areas.
When the environment has changed to become drier and less wooded, especially during the last two million years, the first Homo species began to regularly use tools to break down food or cut the meat. The jaws and teeth have changed to meet a less demanding food source, and the face has become more delicate, with a flatter face.
Changes in the human face may not be due solely to purely mechanical factors. After all, the human face plays an important role in social interactions, emotions and communication. Some of these changes may be dictated, in part, by the social context. Our ancestors have been challenged by the environment and increasingly influenced by cultural and social factors. Over time, the ability to form various facial expressions has probably improved nonverbal communication.
The large prominent brow ridges are typical of some extinct species of our genus, Homo, such as Homo erectus and Neanderthals. What role did these structures play in adaptive changes of the face? African great apes also have strong ridges, which the researchers suggest help to communicate domination or aggression. It is probably safe to conclude that similar social functions have influenced the facial shape of our ancestors and missing relatives. With large, sharp canines, large brow ridges have been lost along the evolutionary path to our own species, perhaps becoming less aggressive and more cooperative in social contexts.
"We are a product of our past," said Kimbel. "Understanding the process by which we became human gives us the right to look at our own anatomy with wonder and ask what different parts of our anatomy tell us about the historical journey to modernity."
Source of the story:
Material provided by University of the State of Arizona. Note: Content can be changed for style and length.
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