We received this email from a PRI educated clinician in Minnesota:
“I just thought I’d pass on some information from a Nova program that was on television recently. A doctor was researching genetic abnormalities associated with muscular dystrophy. He was interested in this field because both his older and younger brothers suffered from the disease.
He found an area in the genetic sequence where muscle genes had been “turned off”. He then tested himself and others who didn’t have the disease and determined that normal individuals also had these genes “turned off.” He then studied the genetic code of chimpanzee’s and the great apes and discovered that their genes were still “on.” He then discovered that the genes in question controlled the size and strength of the masseter (jaw) muscle.
Human masseter muscle has been on the evolutionary decline for some time now and is a fraction of the size found amongst the apes. In fact, the great apes have a masseter approaching the size of our quadriceps muscle. I thought perhaps our muscles have declined because we eat more marshmallows than they do but the doctor had a better explanation.
He reasoned that the greater the size and strength of the masseter muscle, the earlier in life the skull articulations must fuse in order to oppose the muscle’s pull. Ape skull articulations apparently fuse at about 3-4 years of age whereas human skull articulations don’t fuse until approximately 30 years of age. The delayed fusion has allowed our brains (and skull) to expand over the years in contrast to the apes.
The moral of the story is that improving human intelligence and brain size is more important than eating a tough steak.”
Mark Wolf, PT
