More straw clutching
Interesting point. I wonder if anyone on this thread can come up with an explanation.
I think my sister used to date him!
LONDON (Reuters) - A genetic mutation that occurred 2.4 million years ago could be the reason why modern humans have such big brains and weak jaws, scientists said on Wednesday.
They discovered that a fault in a gene called MYH16 in modern humans happened at about the same time that their skulls started to change in shape from other primates, allowing their brains to increase in size.
But the trade-off was a smaller, less powerful jaw.
"The coincidence in time...may mean that the decrease in jaw muscle size and force eliminated stress on the skull which released an evolutionary constraint on brain growth," said Nancy Minugh-Purvis, a member of the team at the University of Pennsylvania School of Medicine, that made the discovery.
All humans have the MYH16 mutation but other primates, including chimpanzees and macaques, still have the intact gene. Over the past few million years, since the genetic fault occurred, human skulls have grown three times in size and the outwardly elongated jaws have receded.
Pete Currie, of the Victor Chang Cardiac Research Institute in Sydney, believes the research published in the science journal Nature could be the first functional genetic difference between humans and apes.
"Remarkably, the timing of the appearance of this genetic alteration, or mutation, roughly coincides with the appearance of "human-like" characteristics in the hominid fossil record," Currie said in a commentary in the journal.
Minugh-Purvis along with Hansell Stedman and other experts at the university pieced together the complicated puzzle after discovering that the gene was intact in primates but mutated in all humans.
A genetic fault is often linked with some type of inherited disease but the scientists were puzzled about what type of disease was common in all humans throughout the world.
Further research revealed that MYH16 was associated with muscles involved in chewing and biting and it encoded a protein in primate jaw muscles. This led the researchers to suspect the so-called disease in humans was a weaker bite.
Stedman and his colleague said the weaker bite would have lessened the force on the skull so it could grow larger and provide more space for a bigger brain.
"We can only hope that this study represents the vanguard of a new wave of analyzes that focus on the genetic basis of human evolution," Currie added.
A genetic mutation that occurred 2.4 million years ago could be the reason why modern humans have such big brains and weak jaws, scientists said Wednesday.
They discovered that a fault in a gene called MYH16 in modern humans happened at about the same time that their skulls started to change in shape from other primates, allowing their brains to increase in size.
But the trade-off was a smaller, less powerful jaw.
"The coincidence in time...may mean that the decrease in jaw muscle size and force eliminated stress on the skull which released an evolutionary constraint on brain growth," said Nancy Minugh-Purvis, a member of the team at the University of Pennsylvania School of Medicine, that made the discovery.
All humans have the MYH16 mutation but other primates, including chimpanzees and macaques, still have the intact gene. Over the past few million years, since the genetic fault occurred, human skulls have grown three times in size and the outwardly elongated jaws have receded.
Pete Currie, of the Victor Chang Cardiac Research Institute in Sydney, believes the research published in the science journal Nature could be the first functional genetic difference between humans and apes.
"Remarkably, the timing of the appearance of this genetic alteration, or mutation, roughly coincides with the appearance of "human-like" characteristics in the hominid fossil record," Currie said in a commentary in the journal.
Minugh-Purvis along with Hansell Stedman and other experts at the university pieced together the complicated puzzle after discovering that the gene was intact in primates but mutated in all humans.
A genetic fault is often linked with some type of inherited disease but the scientists were puzzled about what type of disease was common in all humans throughout the world.
Further research revealed that MYH16 was associated with muscles involved in chewing and biting and it encoded a protein in primate jaw muscles. This led the researchers to suspect the so-called disease in humans was a weaker bite.
Stedman and his colleague said the weaker bite would have lessened the force on the skull so it could grow larger and provide more space for a bigger brain.
"We can only hope that this study represents the vanguard of a new wave of analyzes that focus on the genetic basis of human evolution," Currie added.
In like manner, the smaller jaw turned ape like creatures into humans.
And that's just how many have been flagged for study. It doesn't say how many genetic differences there are.
Sounds a lot more like a lot of design work than random mutations to me.
This makes a bit of sense. Observe this chimp skull:
Without the need for all that extra materal up there to hold the massive jaw muscles, a different -- and separate -- mutation for a larger brain case would then be able to survive. It could pass through the birth canal without killing the baby. One mutation, the relatively trivial one for a smaller jaw, makes the other mutation able to survive.
I don't know the answer to that, but sometimes one mutation has broad spectrum of effects.
First? The hominids had been walking upright for a couple million years before this mutation came along. And their jaws had been smaller than chimp jaws for a long time, too, without any great increase in brain size.
I'm not saying that they haven't uncovered a significant step on the road from ape to man, but it looks like just one out of many.
A pre-human that required tools to eat (because of smaller jaw size), would have started down the evolutionary path to real humans. And it would have started the evolution of a toolmaking culture, which is equally important as the DNA evolution going on.
The key to the article isn't brain size brought on by smaller muscles. It's the beginning of tool making, the biggest definition of humans over apes. (yes I know apes make "tools", but they don't chip rocks into arrowheads)
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