Bite makes way for brain

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iansmith

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A single mutation may have caused gross anatomical changes that spurred human evolution | By Brendan A Maher

A pile of evidence from disparate disciplines indicates that a single change in a single gene—MYH16—may be responsible for significant morphologic differences between humans and other primates, including possibly the three-fold increase in brain size that set the earliest species of Homo apart from their kin. This is the first protein disparity between humans and chimps that can be correlated to drastic anatomical changes seen in the fossil record, according to a group of University of Pennsylvania researchers who published a letter in the March 25 issue of Nature.

“This is a brilliant piece of detective work that has enormous implications for medicine, biology, evolution, molecular genetics, [and] the human genome,” said Frederick S. Kaplan, a professor of orthopedic molecular medicine at Penn who was not part of the study. “By relegating a gene to the evolutionary garbage heap, we were able to lift the constraints to the development of human complexity,” he told The Scientist.

Powerful muscles for biting practically dominate the cranial structures of most primates, including gorillas, chimps, and extinct Australopithecus and Paranthropus species. A gene responsible for a majority of jaw musculature was lost from human ancestors, presumably 2.4 million years ago, according to the study. Drastic reductions in these muscles may have lifted significant physical constraints on braincase volume, allowing primates with weak jaws and big brains to eventually think about their origins.
http://www.biomedcentral.com/news/20040324/04 [Broken]
 
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nautica

One loci causing those kind of changes. Personally, I don't see how that is possible. Has this gone through peer review???

What are your thoughts??

Nautica
 

iansmith

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This original paper has gone through peer review. It will be publish in nature.
http://www.nature.com/nature/links/040325/040325-1.html

The correllation is good but it does not mean that the gene made us smarter. the mutation migth of be the first step towards a bigger brain development.
 

Monique

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Front page art on Nature magazine..
Nautica, this one locus (one loci is kinda contradictory :P) didn't cause these changes, but it allowed it to happen.

The idea is that with the complex muscle attachements it is impossible to change the morphology of the cranium. But since the mutation inactivates the gene, weaker muscles are formed, allowing for modulations of the overall structures.

The fact that it is found in all humans and not in primates really is a tell-all sign that something is going on..
 
It makes no sense to me.

If the human ancestor lost the gene for strong muscle it had still no extra brain to compensate for the obvious loss of fitness.

It would have to compete with same-brained, better jawed specimens.

what do you think?
 

selfAdjoint

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spuriousmonkey said:
It makes no sense to me.

If the human ancestor lost the gene for strong muscle it had still no extra brain to compensate for the obvious loss of fitness.

It would have to compete with same-brained, better jawed specimens.

what do you think?

The only way this could work would be if this population had changed its diet from things (like vegetable materials) that required heavy chewing to things (like half rotten meat) that didn't. So the adoption of a scavenger life style could make the heavy jaw muscles redundant. That wouldn't CAUSE them to shrink, of course - evolution doesn't work that way. But it could PERMIT them to shrink, if development of something else, like an enlarged brain, required it.
 

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