Touching off a scientific furor, researchers say they may have discovered the mutation that caused the earliest humans to branch off from their apelike ancestors - a gene that led to smaller, weaker jaws and, ultimately, bigger brains. Smaller jaws would have fundamentally changed the structure of the skull, they contend, by eliminating thick muscles that worked like bungee cords to anchor a huge jaw to the crown of the head. The change would have allowed the cranium to grow larger and led to the development of a bigger brain capable of tool-making and language. The mutation is reported in the latest issue of the journal Nature, not by anthropologists, but by a team of biologists and plastic surgeons at the University of Pennsylvania and the Children's Hospital of Philadelphia. The report provoked strong reactions throughout the hotly contested field of human origins with one scientist declaring it "counter to the fundamentals of evolution" and another pronouncing it "super 33 minutes ago The Pennsylvania researchers said their estimate of when this mutation first occurred - about 2.4 million years ago, in the grasslands of East Africa, the cradle of humanity - generally overlaps with the first fossils of prehistoric humans featuring rounder skulls, flatter faces, smaller teeth and weaker jaws. And the remarkable genetic mutation persists to this day in every person, they said. Nonhuman primates - including our closest animal relative, the chimpanzee - still carry the original big-jaw gene and the apparatus enabling them to bite and grind the toughest foods. "We're not suggesting this mutation alone defines us as Homo sapiens," said Dr. Hansell Stedman of the University of Pennsylvania School of Medicine. "But evolutionary events are extraordinarily rare. Over 2 million years since the mutation, the brain has nearly tripled in size. It's a very intriguing possibility." University of Michigan biological anthropologist Milford Wolpoff called the research just super." "The other thing that was happening 2 1/2 million years ago is that people were beginning to make tools, which enabled them to prepare food outside their mouths," he said. "This is a confluence of genetic and fossil evidence." Other researchers strenuously disagreed that human evolution could literally hinge on a single mutation affecting jaw muscles, and that once those muscles were reduced, the brain suddenly could grow unfettered. "Such a claim is counter to the fundamentals of evolution," said C. Owen Lovejoy of Kent State University. "These kinds of mutations probably are of little consequence." Others sought to find some middle ground in the debate. University and commercial laboratories rapidly are comparing the human genome with that of chimpanzees to determine what makes people human, and how the earliest transitional creatures known as hominids split from Old World apes and monkeys some 6 million years ago. So far, perhaps 250 genetic differences 250 genetic differences have been flagged for further study. Jaws have been a focus of evolutionary research since Darwin, and the mutation offers a tantalizing theory. But it is unlikely that one mutation - even at a crucial evolutionary juncture - would make a person, some skeptics said. "They have successfully nailed a genetic mutation that works to deactivate these jaw muscles," said Richard Potts, director of the Human Origins Program at the Smithsonian Institution. "But their suggestion connecting it to the brain is way too speculative."
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Quite interesting, I hope they look into it further. What's the question?
