Genetics and the Evolution of the Human Brian

Oncedeceived said:

What is the connection to this gene to actual increase in brain size. Meaning how does the correlation of larger space equate to larger brain?

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SteveB28 said:

I would imagine this is regarded as just another piece of evidence. If the human brain has evolved in the manner in which evolutionary theory predicts that it would have, then we should be able to find evidence that supports this. The mechanism for permitting the possibility of a bigger cranial cavity would be one such piece of supporting evidence. This is not to suggest that a bigger brain, in and of itself, is the sole determinant of increased human intelligence, but it appears to be one ingredient.

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SteveB28 said:

I would imagine this is regarded as just another piece of evidence. If the human brain has evolved in the manner in which evolutionary theory predicts that it would have, then we should be able to find evidence that supports this. The mechanism for permitting the possibility of a bigger cranial cavity would be one such piece of supporting evidence. This is not to suggest that a bigger brain, in and of itself, is the sole determinant of increased human intelligence, but it appears to be one ingredient.

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OldWiseGuy said:

Why would the skull cavity get larger just because the jaw gets smaller, especially if it now is larger in relation to the smaller jaw? And if the skull did get larger it would more likely happen because of the pressure of an enlarging brain, not an expanding skull. But then why would the brain get larger? Certainly not from more mental activity, which it would not be able to accomplish due to the limitations of it's size. But if it could accomplish greater mental activity why would it need to expand in size? That would require restructuring the whole body of the critter to carry around this new oversized head.

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Oncedeceived said:

When did this "prediction" of how the human brain should have evolved and that it evolved in this manner?

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mark kennedy said:

Because the effects of mutations in brain related genes are always deleterious.

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Natural Selection is nothing more then an assumption:

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Mutations are a failure of DNA repair:

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I'm not expecting one.

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It's a direct question with a comprehensive answer, akin to what is 3 plus 1:

Single-nucleotide substitutions occur at a mean rate of 1.23%...On the basis of this analysis, we estimate that the human and chimpanzee genomes each contain 40–45Mb of species-specific euchromatic sequence, and the indel differences between the genomes thus total ~90Mb. This difference corresponds to ~3% of both genomes and dwarfs the 1.23% difference resulting from nucleotide substitutions (Initial Sequence of the Chimpanzee Genome, Nature 2005)​

Yet when announcing the results in their web focus article they say it's 98%:

What makes us human? We share more than 98% of our DNA and almost all of our genes with our closest living relative, the chimpanzee. (The Chimpanzee Genome)​

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I'm not expecting one, that much is sure.

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SteveB28 said:

I'm not sure what your question means - I'm assuming there are a few words missing ?

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Oncedeceived said:

You said it was a prediction that the brain would be larger and that the prediction included in what manner it would evolve. Understand my question now?

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SteveB28 said:

Somewhat. The "when" threw me. Are you asking when such a prediction was made, or when the enlargement of the human skull occurred?

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Oncedeceived said:

When did this "prediction" of how the human brain should have evolved and that it evolved in this manner?

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Oncedeceived said:

Yes, when and in what manner were you referring to?

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Gracchus said:

There is some evidence that the brain development of humans was an indirect result of a mutation that weakened human musculature. The reduction of the strength of the jaw muscles allowed the skull to continue to expand beyond of the limits of those primates with stronger muscles.

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