Chins Revisited -- A Reader Writes
A reader, Dr. Myer S. Leonard, DDS, MD, writes:
I enjoyed reading your article on chins in this morning's Evolution News ["On the Origin of Chins"]. Until 15 years ago I was professor of maxillofacial surgery at the University of Minnesota and one of the most popular lectures I gave was "Get a Chin, Get Ahead." In this I would show slides of many famous leaders, models, and other folk in the public eye and then have their chin airbrushed out of the picture. The change was so staggering that everyone agreed none of them would've been elected or chosen to be models or achieved much in the public eye. Of course there were exceptions -- Mrs. Thatcher did not have much of a chin!
I had looked at the skulls of many animals from rodents to lions and bears and as you so rightly point out none of them had a chin. With my colleagues I did some biomechanics testing and one of the things that we came to realize was that in every animal we examined there is simply cartilage at the symphyseal region [where the two halves of the jaw grow together], joining what in effect are two independent beams. The human chin is a continuum and when we put gauges on the left side of the chin we could see the stress and compression components would be passed through the area of the chin, whereas when we did this on animal skulls we saw less transmission of the forces to the opposite jaw.
One of the features of patients who consulted me because of microgenia [having an unusually small or deformed chin] was that their eyes ("the windows of the soul") often lacked any "fire" and after the surgery one could see the biggest transformation was in the glint of their eye! Indeed, several of them modified their personalities quite appreciably to be slightly more assertive.
It is funny how in the popular mind a prominent chin (e.g., Dick Tracy) is thought to be related to a somewhat pugnacious personality and a recessive chin to a somewhat docile personality.
Thank you, Dr. Leonard! We enjoyed your fascinating letter.
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