Creationism and Human Brain evolution

[mark kennedy]

Greetings debaters,

I bring you yet another renunciation of the much celebrated, never demonstrated, often pontificated, single common ancestor model...but seriously folks. Let us ponder the the most signifigant questions confronting the single common ancestor model in our day. What makes us human? (Nature 437, 69-87 ) What is the genetic basis for the threefold expansion of the human brain in 2 1/2 million years?(Genetics, Vol. 165, 2063-2070) What is the genetic and evolutionary background of phenotypic traits that set humans apart from our closest evolutionary relatives, the chimpanzees?(Genome Research 14:1462-1473)

One of the problems with the evolutionary expansion of the human brain from that of an ape is the size, weight and complexity. The human brian would have had to triple in size, starting 2 1/2 million years ago and ending 200 to 400 thousand years ago. The brain weight would have had to grow by 250% while the body only grows by 20%. The average brain weight would have to go from 400-450g, 2 1/2 MY ago to 1350–1450 g 0.2–0.4 MY.

"It is generally believed that the brain expansion set the stage for the emergence of human language and other high-order cognitive functions and that it was caused by adaptive selection (DECAN 1992 ), yet the genetic basis of the expansion remains elusive."

Evolution of the Human ASPM Gene, a Major Determinant of Brain Size, Genetics, Vol. 165, 2063-2070, December 2003

Jianzhi Zhang tried to determine if positive selection of amino acid substitutions that left the reading frame open are detectable in the ASPM gene. He instead found strong purifying selection and concluded that the postive selection of the ASPM gene took place time between 6–7 and 0.1 MY ago (0.5 x 10,000 generations x 20 years/generation). Researchers have determined that the gene is still evolving but I wonder how a congenital developmental defect characterized by severely reduced brain size could be an advantage.

Overall genetic differences create a problem since the size of the genetic differences is growing. Type 'DNA simularities between humans and chimpanzees' into a google search engine and you will find estimates close to 99%. Growing evidence has determined that these estimates are just plain wrong. The divergance has been found to include indels of considerable length, in the comparision of the Chimpanzee Chromosome 22 and its counterpart Human Chromosome 21 found that 83% of chimpanzee chromosome 22 proteins are different from their human counterparts.

"Sakaki said their analysis found about 68,000 insertions or deletions. "That is almost one insertion/deletion every 470 bases," he said. In addition, a small proportion of genes showed a relatively higher rate of evolution than most other genes. "We haven't known what proportion of the genes shows adaptive evolution. This study shows it to be about 2 to 3%," he said."

Chimps are not like humans Whole-chromosome comparison reveals much greater genetic differences than expected

More recently, the Chimpanzee Genome project published their highly anticipated Initial sequence of the chimpanzee genome and comparison with the human genome, Nature 437, 69-87 (1 September 2005). What they found was the the differences between the chimpanzee and human genomes have a 35 million nucleotide difference with five million insertion/deletion events, and various chromosomal rearrangements. This would include a 3 million bp divergance in the function part of the genome effecting vital functions.Even by conservative estimates the fixation of single base substitutions, insertions, deletions and polymorphisms (including chromosomal rearrangements) would have to average anywhere from 3 to 7 bp differences, fixed in the respective geneomes, per year for humans to evolve from apes. The most important of these would be the human brain with the most important changes occuring in the cerebral cortex.

Consumed with incredulity I started to wonder how the genes effecting brian function were related to the presumed common ancestor of Man and Chimpanzee. What I found was astonishing and I don't mean the differences between chimpanzees and humans, which are considerable. The differences within their respective species and, even more supprising, from one individule to another are far larger then I realized. In fact, 22% of the genes that showed differences between humans and chimpanzees where due to differences between individules within their respective species.


What follows is from Regional Patterns of Gene Expression in Human and Chimpanzee Brains . Apparently the transcriptomes differ more between individules then between regions. In comparing human and chimpanzee genes differ by 10% in at least one region with the majority being shared in all others. I will make every attemp not to exaggerate the differences nor dismiss the simularities. I, like most people interested in the theory of evolution, am interested in the genetic basis of evolution.

"The draft sequence of the chimpanzee genome will allow most nucleotide differences between the two species to be listed. However, to interpret these differences in terms of function, an important step is to know how gene expression has changed between humans and chimpanzees. Because several important phenotypic differences that distinguish humans and apes are associated with cerebral activity, it is of particular interest to investigate the gene expression patterns in brains of humans and chimpanzees."​

Figure 1 Location of areas sampled from the human cerebral cortex.​

The cerebral cortex in involved in many complex brain functions including memory, attention, perceptual awareness, "thinking", language and consciousness.

"In the cerebral cortex, the biggest difference in gene expression is between the primary visual cortex and the anterior cingulate cortex in both humans and chimpanzees, where 193 and 227 genes differ in expression in humans and chimpanzees, respectively."


The primary visual cortex has been observed to have distinct differences between chimpanzees and other primates considered to be related to humans. The human nonphosphorylated neurofilaments (NPNF) is denser with embedded cell bodies, were intermingled with lightly stained territories, giving the layer a mesh-like appearance. (Cerebral Cortex, Vol. 12, No. 7, 671-691, July 2002)

In other regions the differences are close to nonexistant.

"Only one gene out of the 4998 genes with detectable expression differs in expression between Broca's area and the left prefrontal cortex in all three humans analyzed and none in chimpanzees."

Figure 3 Number of genes exhibiting expression patterns specific to brain regions in humans and chimpanzees.

In all the differences amount to:

"406 differentially expressed genes for which the chimpanzee DNA sequence is known, 207 are more highly expressed in humans and 199 in chimpanzees."

What is the explanation that is most often used to explain the level of divergance in genes affecting the brain? Welcome to the wonderfull world of duplications. Chromosomes 1, 2, 4, 5, 9, 12, 15, 16, 17, and 18, are known sites of signifigant differences between chimpanzees and humans. Instead of differences modern researchers simply insert the word selection instead of admitting the coding regions have distict structural differences. In the conclusion they assume that these chromosomal rearrangements led to speciation because they lead to lower recombination in the heterokaryotypes.

"Gene expression differences between humans and chimpanzees are furthermore associated with regions of segmental duplications in the human genome Table 5 . This association is seen for genes that show higher expression levels in humans than in chimpanzees, whereas there is no statistically significant association with genes that are more highly expressed in chimpanzees."

They are still propagating the idea that we are 99% identical to the chimpanzee and this is not only wrong, it is shamefull. If there is going to be a substantive discussion of what shapes the diversity alleles in populations over time the actual differences should be accounted for. Here is a fairly typical statement of fact that has been proven wrong conclusivly. Submitted as a post script for your general interest and amusement.

"Humans are 99.9% alike genetically, and that 0.1% makes all the difference in terms of appearance, personality, and susceptibility to disease. That 0.1% promises to shed light on the evolutionary forces that control genetic variation as well as the genetic origins of human disease."

A DNA Recombination “Hotspot” in Humans Is Missing in Chimps

We are talking about what makes us human and the genetic basis of our supposed shared common ancestory with chimpanzees. Will they and those who made these erroneous statement in the past now revise their statements? If they do the recombination rate and segmental gene duplications just got harder to demonstrate, four to five times harder in fact. In the case of human genes expressed in the brain as compared to the chimpanzee its more like ten.

 

[notto]

Mark, are you suggesting that all of the specimins with intermediate brain size and body mass were specially created along with humans and chimps?

What 'kind' are they?

 

[mark kennedy]

Mark, are you suggesting that all of the specimins with intermediate brain size and body mass were specially created along with humans and chimps?

What 'kind' are they?

They are fagmentary, anecdotal evidence of epochs of history that are speculated about endlessly. The genetic basis for this unprecedented evolutionary change is unknown, and IMO, impossible.

 

[Loudmouth]

Mark,

I think you are making some fundamental errors in your essay. You switch in between gene expression and gene sequence. These are actually two different mechanisms that can create phenotypic differences. For instance, it is possible that switching a human gene for a chimp gene may not affect phenotype. Instead, it is when the gene is expressed and how strongly the gene is expressed which results in the observed phenotype.

Secondly, it is still not known what each gene is responsible for in both humans and chimps. Without knowing gene function how is it possible to discount common ancestory?

Thirdly, handwaving fossil evidence is not going to help your case. The fossils are real, even if you don't want them to be.

 

[mark kennedy]

Mark,

I think you are making some fundamental errors in your essay. You switch in between gene expression and gene sequence. These are actually two different mechanisms that can create phenotypic differences. For instance, it is possible that switching a human gene for a chimp gene may not affect phenotype. Instead, it is when the gene is expressed and how strongly the gene is expressed which results in the observed phenotype.

It may well be true that I make certain errors in the specifics related to gene expression and gene sequence. My interest in the paper was the level of divergance and the genetic basis.

"22% of the genes classified as differentially expressed between humans and chimpanzees are caused by nucleotide sequence differences between the species." (see Estimating the Effect of Interspecific DNA Sequence Differences)

Secondly, it is still not known what each gene is responsible for in both humans and chimps. Without knowing gene function how is it possible to discount common ancestory?

Without knowing why is it nessacary to assume it? It is presumed across the board and as long as the nucleotide seqeunces are virtually identical it makes sense. Otherwise, I think independant lineage makes a lot more sense.

Thirdly, handwaving fossil evidence is not going to help your case. The fossils are real, even if you don't want them to be.

I'm not handwaving them away, the human brain would have had to triple in size because of the fossil evidence, not dispite it.

 

[Loudmouth]

It may well be true that I make certain errors in the specifics related to gene expression and gene sequence. My interest in the paper was the level of divergance and the genetic basis.

"22% of the genes classified as differentially expressed between humans and chimpanzees are caused by nucleotide sequence differences between the species." (see Estimating the Effect of Interspecific DNA Sequence Differences)

And all we get, again, is incredulity. For example (from the OP):

"One of the problems with the evolutionary expansion of the human brain from that of an ape is the size, weight and complexity. The human brian would have had to triple in size, starting 2 1/2 million years ago and ending 200 to 400 thousand years ago. The brain weight would have had to grow by 250% while the body only grows by 20%. The average brain weight would have to go from 400-450g, 2 1/2 MY ago to 1350–1450 g 0.2–0.4 MY."

Why is this a problem? What prevents mutations from causing this brain increase? (sidenote: I think it is 400-450 cc, not grams).

Without knowing why is it nessacary to assume it? It is presumed across the board and as long as the nucleotide seqeunces are virtually identical it makes sense. Otherwise, I think independant lineage makes a lot more sense.

Since evolution suggests that all mammals share a common ancestors does this mean, according to you, that all mammals should be almost identical at the DNA level?

I'm not handwaving them away, the human brain would have had to triple in size because of the fossil evidence, not dispite it.

And yet these fossils are intermediate between chimps and humans, exactly what we would expect if evolution were true. If special creation were true we would not expect any intermediates.

 

[mark kennedy]

And all we get, again, is incredulity. For example (from the OP):

"One of the problems with the evolutionary expansion of the human brain from that of an ape is the size, weight and complexity. The human brian would have had to triple in size, starting 2 1/2 million years ago and ending 200 to 400 thousand years ago. The brain weight would have had to grow by 250% while the body only grows by 20%. The average brain weight would have to go from 400-450g, 2 1/2 MY ago to 1350–1450 g 0.2–0.4 MY."

Why is this a problem? What prevents mutations from causing this brain increase? (sidenote: I think it is 400-450 cc, not grams).

Deleterious effects. Most of the adaptive evolution going on are related to high levels of recombination, not random mutations. (its grams, the context of the statement was the difference in weight)

Since evolution suggests that all mammals share a common ancestors does this mean, according to you, that all mammals should be almost identical at the DNA level?

Evolution does not suggest common ancestors, it looks at changing alleles in populations over time and discovers that many of them do have common ancestors. This is what creationism would expect when the created kinds spread and multiply according to their kinds. Single common ancestory is another thing entirely and the evidence goes just as far to suggest independant lineage of higher taxa, if not more. What is more, all mammals are not virtually identical even between chimpanzees and humans. If there is 40 million nucleotide divergance between Man and Apes then how far do you think we have diverged from new world monkeys? The DNA is allways going to be simular because the there are only four different nucleotides matched up in pairs.

And yet these fossils are intermediate between chimps and humans, exactly what we would expect if evolution were true. If special creation were true we would not expect any intermediates.

Intermeditates that would have had to triple the size of their brains starting 2 1/2 million years ago in size weight and complexity. The genetic basis is unknown so without a demonstrated or directly observed molecular mechanism you have an a priori assumption.

 

[AirPo]

They are fagmentary, anecdotal evidence of epochs of history that are speculated about endlessly. The genetic basis for this unprecedented evolutionary change is unknown, and IMO, impossible.

So what you're saying is that we don't know therefore Go did it?

 

[mark kennedy]

So what you're saying is that we don't know therefore Go did it?

No, I am saying that the divergance between humans and chimpanzees is much higher then we have been led to believe. With a 40 million nucleotide difference between chimpanzees and humans, 3 million of them in the functional part of the gene special creation is still a viable alternative to the single common ancestor model. In fact, it makes a lot more sense.

 

[Pete Harcoff]

So what you're saying is that we don't know therefore [God] did it?

You've just summed up the entire creationist position.

 

[AirPo]

No, I am saying that the divergance between humans and chimpanzees is much higher then we have been led to believe. With a 40 million nucleotide difference between chimpanzees and humans, 3 million of them in the functional part of the gene special creation is still a viable alternative to the single common ancestor model. In fact, it makes a lot more sense.

I don't see how that follows at all. We increase our understanding, you say that's even more unbelieveable, therefore special creation?

 

[ImmortalTechnique]

A PERFECT AD FOR THIS THREAD:

Join 1000s of K12 students & adults for free online study of Narnia. www.TheNarniaAcademy.org
<IMG height=1 alt="" width=1>Ads by Google
<IMG height=1 alt="" width=1>

 

[AirPo]

You've just summed up the entire creationist position.

Bad habit of mine

 

[Loudmouth]

Deleterious effects. Most of the adaptive evolution going on are related to high levels of recombination, not random mutations.

Recombinations are random and they are mutations. Did you mean point mutations?

Evolution does not suggest common ancestors, it looks at changing alleles in populations over time and discovers that many of them do have common ancestors.

The theory of evolution states that all life originated from a single ancestor. Did you miss that part?

This is what creationism would expect when the created kinds spread and multiply according to their kinds.

Yep, the eukaryote kind and the prokaryote kind.

Single common ancestory is another thing entirely and the evidence goes just as far to suggest independant lineage of higher taxa, if not more.

I'll concede to different origins for eukaryotes and prokaryotes. However, I don't think this is what you are shooting at. Care to give us the objective criteria for determining what does and doesn't belong in the same kind? Are humans and chimps in the Hominidae Kind?

If there is 40 million nucleotide divergance between Man and Apes then how far do you think we have diverged from new world monkeys?

Why do new world monkeys have nucleotides if they were created separately?

The DNA is allways going to be simular because the there are only four different nucleotides matched up in pairs.

They were created separately, so why do they share DNA? Birds and bats do not share feathers or nipples, so why say that it makes sense that birds and bats share the same genetic molecule?

What is more, all mammals are not virtually identical even between chimpanzees and humans.

Yes, it's called random mutation.

With a 40 million nucleotide difference between chimpanzees and humans, 3 million of them in the functional part of the gene special creation is still a viable alternative to the single common ancestor model. In fact, it makes a lot more sense.

Uhh, weren't you the one who said the following:

"The genetic basis is unknown so without a demonstrated or directly observed molecular mechanism you have an a priori assumption."

So not knowing the exact genetic mechanism for brain increases is a problem for evolution but not having any evidence for a supernatural creator is no problem at all? You're joking, right?

 

[AngelusTenebrae]

Deleterious effects. Most of the adaptive evolution going on are related to high levels of recombination, not random mutations.

Genetic recombination also works. Deletion of gene sequences may be loss of information, but perhaps it was the loss of a codon that would code for an amino acid in a protein chain. So if we remove that amino acid and it becomes another substance, possibly a better one, one that may help produce a larger or better brain, that could work. The only implication of "deleterious effect" is removing a gene sequence as related to the production of a protein. But removing or adding an amino acid from a protein chain doesn't say much about whether the protein is beneficial or not. It is the identity of the protein, where it is being used, and the interactions with other substances that is more significant.

Evolution does not suggest common ancestors, it looks at changing alleles in populations over time and discovers that many of them do have common ancestors. This is what creationism would expect when the created kinds spread and multiply according to their kinds. Single common ancestory is another thing entirely and the evidence goes just as far to suggest independant lineage of higher taxa, if not more. What is more, all mammals are not virtually identical even between chimpanzees and humans. If there is 40 million nucleotide divergance between Man and Apes then how far do you think we have diverged from new world monkeys? The DNA is allways going to be simular because the there are only four different nucleotides matched up in pairs.

Ever heard of asexual reproduction? All that's required is a single common ancestor. Either it has mutations, or it uses this thing called conjugation, which amounts to sexual reproduction, or more importantly, genetic recombination. Given that we've been around for quite a while, and evolution of primates would have been millions of years ago, it's not difficult to see chaneg in 40 million nucleotides, since we're also considering generations of a reasonable population of primates.

Intermeditates that would have had to triple the size of their brains starting 2 1/2 million years ago in size weight and complexity. The genetic basis is unknown so without a demonstrated or directly observed molecular mechanism you have an a priori assumption.

The precursors of brains is the ganglion. Mutations or genetic recombination resulted in cephalization, the centralizing of a group of ganglion in one region. With natural selection, this would shift the development of the nervous system towards a primitive brain, and eventually, better ones.

 

[mark kennedy]

I don't see how that follows at all. We increase our understanding, you say that's even more unbelieveable, therefore special creation?

No, we don't increase out understanding, our brain would have to triple in size, which would be an unprecedented evolutionary process. No one has ever seen positive selection on this level but if the alternative is God we have to reject it, irregardless of whether or not we have a genetic basis for the change.

 

[AngelusTenebrae]

No, we don't increase out understanding, our brain would have to triple in size, which would be an unprecedented evolutionary process. No one has ever seen positive selection on this level but if the alternative is God we have to reject it, irregardless of whether or not we have a genetic basis for the change.

In science, God is not an alternative. This selection for the brain would be helped by bipedalism, so if the idea was increase in intelligence and tool making, then increased brain size is a preadaptation after bipedalism. You can't imagine a cow picking up a phone now, can you?

 

[AirPo]

No, we don't increase out understanding,

I meant now that we've mapped the chimp genome.

our brain would have to triple in size, which would be an unprecedented evolutionary process.

Why is that a problem? You're not implying that it happened all at once are you?

No one has ever seen positive selection on this level but if the alternative is God we have to reject it, irregardless of whether or not we have a genetic basis for the change.

That's a mighty big IF. And it doesn't follow logically.

 

[Loudmouth]

No, we don't increase out understanding, our brain would have to triple in size, which would be an unprecedented evolutionary process.

There are many unprecedented evolutionary changes. That's kind of what you would expect from a blind process. Why is this one a problem?

No one has ever seen positive selection on this level but if the alternative is God we have to reject it, irregardless of whether or not we have a genetic basis for the change.

Look at the changes seen in dogs. Nothing in nature has ever created such diversity in such a short time.

Oh, and how did you rule out Leprechauns as another alternative? Flying Spaghetti Monster? Why play God-of-the-Gaps?

 

[Dr.GH]

Well, it is nice to see that Mark can use the PubMed search, or maybe Google Scholar. But what in the world makes you think, Mark, that the genomic sequence of the Chimp is an evolutionary dilemma? From the abstract of the The Chimpanzee Sequencing and Analysis Consortium whoes article you cited:

Here we present a draft genome sequence of the common chimpanzee (Pan troglodytes). Through comparison with the human genome, we have generated a largely complete catalogue of the genetic differences that have accumulated since the human and chimpanzee species diverged from our common ancestor, constituting approximately thirty-five million single-nucleotide changes, five million insertion/deletion events, and various chromosomal rearrangements. We use this catalogue to explore the magnitude and regional variation of mutational forces shaping these two genomes, and the strength of positive and negative selection acting on their genes. In particular, we find that the patterns of evolution in human and chimpanzee protein-coding genes are highly correlated and dominated by the fixation of neutral and slightly deleterious alleles. We also use the chimpanzee genome as an outgroup to investigate human population genetics and identify signatures of selective sweeps in recent human evolution.