The importance of the chin to the human body has been the subject of numerous debates over the years with no definite answer in sight. A new study, however, offers to settle the argument by shedding light on the chin's purpose.
Researchers from the University of Florida discovered that the development of the chin, as it is seen today, is the result of key changes in man's eating habits 6 million years ago. The change in diet to softer meat and the introduction of cooking techniques allowed early humans to eliminate the need for big, powerful mandibles and, as a consequence, the jaw became smaller over time.
Dr. James Pampush and his team collected chin data from more than 100 species of primates and cross-referenced them with historical records. Through computer modelling, the team traced the changes in alignment of the front of the jaw and the degree at which it evolved.
The study, published in the Journal of Human Evolution, found no evidence of genetic drift, or random occurrence, citing that the chin developed 77 times faster than the normal rate observed for features on a primate. The researchers could not find any proof that the chin served a definite purpose.
In a recent interview, Dr. Pampush presented his theory behind the importance of the chin.
"Most people outside of anthropology are surprised to learn that humans are the only animal that has a chin," Pampush said. "It's such an unusual feature that in a way it sort of helps define what it means to be human."
Pampush went on to explain in another statement the development of the lower portion of the mandible.
"Around 2 million years ago, there were a lot of changes to the 'human-like' animals. Homo erectus had a larger body size, much larger brains, was probably cooking and there's a good chance they were using clothing. They are very human-like, but had no chins. I'm guessing the changes which ultimately lead to the chin are directly related to cooking, and indirectly related to larger brains and bodies."
Pampush stated that the invention of cooking allowed the Homo erectus to spend less time in eating. This led to the teeth becoming smaller, and the decrease in the size of the teeth gave the chin its spandrel look.
The new study presented by the University of Florida contrasts against previous theories that the chin evolved as an example of sexual selection. These earlier notions suggest that men with well-defined chins are likely to make good mates.
Another theory claimed that the chin serves to balance the stress put on the mandible during chewing, but Pampush's research also cast doubt on that idea.
Photo: Caitlin Regan | Flickr
