Researchers have proposed a new answer to the question of how the human brain has grown so large. They believe that our unique thinking abilities we have to … weak jaw muscles. A mutation that occurred 2.4 million years ago, the ancestors could deprive people of the ability to produce one of the major proteins of the jaw muscles. In the absence of restrictions in the form of a bulky chewing apparatus human skull got freedom to grow.
• Jaws people are much weaker than in monkeys
Time of occurrence of this mutation coincided with a time of rapid growth of the brain, which occurred, according to the paleoanthropologists, about two million years ago, says Nancy Menofia-Purvis, from the University of Pennsylvania. The culprit of this, apparently, was the protein MYH16, an important component of powerful jaw muscles of many non-human primates. When the researchers analyzed samples of human DNA from around the world, they found that we all have a defect in the gene encoding this protein. With the help of the rate of evolution, they determined the age of the mutation. Comparing the human skull with heads of other primates, they noted that even dalnorodstvennye primate species featured powerful ridges on the skull, to which were attached the heavy muscles of the jaw.
These details on human skulls were missing, despite the close family ties with the gorillas. Our skulls could lose these ridges when the muscles ceased to have too much impact on the skull. After parting with large attachments for muscles, the skull had the opportunity to acquire a modern rounded shape. After all, powerful jaws are incompatible with a powerful brain.