Gene Involved in Brain Development Evolved Rapidly in Humans

[mark kennedy]

And this precise effect explains why the gene has remained almost completely unchanged for so long, until a large selection pressure in favor of change in that gene occurred.

Natural selection preserves a favored trait, it does not produce it. You are ignoring the need for the nucleotide sequence to be altered in the first place. This makes no sense whatsoever, you have the effect before the cause.

But the scenario where the mutation results in a meaningless amino acid only make it easier to produce a beneficial mutation! If the mutation is that destructive to the coding, the fetus would be unlikely to survive at all, and the parents would be able to try again much more quickly.

So how many lethal mutations do you think nature tinkers with before it gets lucky. It's like winning the lottery at least three times in a row, did you forget this?

That is all the possiblities that you have to work with. What happens when a single nucleotide is substituted in one of those amino acids? What do you estimate the probability that it will be transposed into a meaningfull sequence? I only ask because we are looking at 6 with how many lethal mutations left in the wake?

Unfortunately, I don't think anybody knows the exact probabilities of each kind of mutation. I mean, you have four possibilities:
1. A destructive mutation (fetus does not survive, either for very long in the womb, or for very long after).
2. A mutation that has no effect (won't spread through the population as a whole).
3. A mutation that degrades the survivability or reproductive capability of the organism (certainly won't spread through the population).
4. A mutation that increases the survivability or reproductive capability of the organism (will spread relatively quickly).

I don't know, this is such an intelligent answer I am just going to leave this statement alone with my full agreement.

Unfortunately, of the ~400 possible insertion/change mutations in the gene, I don't think we have any way of knowing how many fit into each category. But we could just take the worst-case scenario, and state that only those 18 mutations which separate us from our ape brethren are beneficial to brain development (highly, highly unlikely, but why not, for the purpose of argument?).

I am not sure but I think you may have an interesting proposition here. We would need to know the exact amino acid sequence but it would be fun to try. If you have 64 possible combinations of the 4 nucleotides involved in all DNA (4*4*4), then you are limited are you not? If we know the exact amino acid sequence of both ape and man in this gene we could probably come up with a scenerio. I'll do some looking around but I'm not promising anything.

Now, still with the assumption of ~100,000 hominid population, we know that any mutation in the HAR1 gene will happen about once every generation.

There is really no chance that populations approached 100,000. They were limited to central Africa up until just over a million years ago, there is no way populations approached that many, it was more likely around 10,000.

But the probability for this mutation to be beneficial is about ~1/20. So it takes 20 generations for a beneficial mutation to occur. But there's still a relatively high mortality rate among humans, so even though we have rather high selection pressure in favor of well-developed brains, there's still a significant chance the hominid child in question won't ever grow up. So let's say it takes, on average, fifty tries for that gene to survive until it can actually spread.

I don't know what you are doing with this hypothetical but it begs the question of the gene actually being changed.

So that's one mutation every 1000 generations that spreads throughout the population. Once the mutation has occurred, as long as the selection pressure is there, it will spread throughout the entire population. So we have 18 of these mutations to perform, or 18000 generations. Let's bump it up to a good round 20000 generations.

Ok, let's see what you do with half a million years to accumulate 18 substitutions in a highly conserved gene.

If every generation is 20 years, we have a mere 400,000 years required for the HAR1 gene to change all 18 base pairs.

So, combining a near worst-case scenario for the probability of a mutation being beneficial, and adding in a 1/50 chance that that mutation will spread throughout the genome, we still have a miniscule time scale, in evolutionary terms, for the full gamut of changes in the HAR1 gene to have occurred.

That is amazingly general rationalization of a very specific sequence. While I do enjoy watching you applying the rate of spontaneous mutations to overall divergance it does not apply to a specific gene like this one. First you have to find a beneficial effect from a mutation in a gene effecting the developing human brain.

Good luck with that one because I have yet to even see a mere mention of one and I have been doing this for a couple of years now.

 

[rmwilliamsll]

I really doubt that's going to happen very often, though.


find out if a few human pseudogenes have been completely sequenced. what is the average number of mutations in the pseudogenes versus the functional copies?

i don't have the time tonight but perhaps will tomorrow to research this issue.

 

[Chalnoth]

So how many lethal mutations do you think nature tinkers with before it gets lucky. It's like winning the lottery at least three times in a row, did you forget this?

I never claimed otherwise. But the fact that many mutations in an active gene will be destructive means that those mutations that are beneficial are more likely to occur (since presumably human ancestors, just like humans today, would have given birth more often if an offspring dies than if that offspring lives).

Ok, let's see what you do with half a million years to accumulate 18 substitutions in a highly conserved gene.

To answer this question, you have to ask why it was conserved for so long in other species. The short answer is certainly natural selection. It is entirely possible that in no other mammal or bird was intelligence favored so much as it was in our hominid ancestors, enough so that our ancestors may have been capable of dealing with possibly deleterious side effects in order to obtain higher intelligence.

 

[birdan]

That is amazingly general rationalization of a very specific sequence. While I do enjoy watching you applying the rate of spontaneous mutations to overall divergance it does not apply to a specific gene like this one. First you have to find a beneficial effect from a mutation in a gene effecting the developing human brain.

Good luck with that one because I have yet to even see a mere mention of one and I have been doing this for a couple of years now.

How about two examples?

-the microcephalin gene. A variant arose sometime between 14,000 and 60,000 years ago.

-the ASPM gene, whose variant arose approximately 5,800 years ago.

These variants are so recent (evolutionarily speaking) that they are not fully dispersed throughout the population. And possibly these variants were instrumental in the development of toolmaking and written language, resp. At any rate, both genes regulate brain growth, and since the variants have dispersed through some 70+% of the population, they probably aren't detrimental changes, at the very least.

 

[mark kennedy]

find out if a few human pseudogenes have been completely sequenced. what is the average number of mutations in the pseudogenes versus the functional copies?

Think about it, you are talking about some kind of a pseudogene. I am talking about a reulatory gene involved in the development of the neocortex.

i don't have the time tonight but perhaps will tomorrow to research this issue.

I think you should, I provided the abstact and a link to a really good discussion on the subject. If you need anything just let me know.

Grace and peace,
Mark

 

[mark kennedy]

I never claimed otherwise. But the fact that many mutations in an active gene will be destructive means that those mutations that are beneficial are more likely to occur (since presumably human ancestors, just like humans today, would have given birth more often if an offspring dies than if that offspring lives).

This is not such a complicated issue, the gene is highly conserved for 310 million years, then about 2 million years ago it diverges in a big way. Normal natural selection is not an answer, what was the first cause is the question.

To answer this question, you have to ask why it was conserved for so long in other species. The short answer is certainly natural selection.

You allways have to play that wild card and the fact of the matter is it's not an answer. In order for natural selection to act there has to be a change in the nucleotide sequence. Natural selection did not wave a magic wand because it would be benefical, it only preserves what is allready there...but you were saying...

It is entirely possible that in no other mammal or bird was intelligence favored so much as it was in our hominid ancestors, enough so that our ancestors may have been capable of dealing with possibly deleterious side effects in order to obtain higher intelligence.

I don't want to be rude but no it's not entirely possible for a gene to change like this just because it would be an advantage. Sure it would be preserved if it happened but it does not happen.

Bottom line, natural selection is not an answer it's an a priori assumption of a common ancestor.

 

[mark kennedy]

How about two examples?

Oh that would be fun!

-the microcephalin gene. A variant arose sometime between 14,000 and 60,000 years ago.

You do know that it results in a smaller brain right, how is that a selective advantage?

-the ASPM gene, whose variant arose approximately 5,800 years ago.

An abnormal spindle is your idea of evolution? Come on, there is no selective advantage to be had.

These variants are so recent (evolutionarily speaking) that they are not fully dispersed throughout the population. And possibly these variants were instrumental in the development of toolmaking and written language, resp. At any rate, both genes regulate brain growth, and since the variants have dispersed through some 70+% of the population, they probably aren't detrimental changes, at the very least.

So it's possible that this genetic mutation that reduces the human brain is the key to understanding our history? I don't know what kind of a variant you are talking about here, I am talking about the HAR1 gene. The one that produces an abnormal spindle is an interesting one but not going to qualify as a demonstrated or directly observed mechanism.

 

[Chalnoth]

I don't want to be rude but no it's not entirely possible for a gene to change like this just because it would be an advantage. Sure it would be preserved if it happened but it does not happen.

Bottom line, natural selection is not an answer it's an a priori assumption of a common ancestor.

It doesn't change just because it would be an advantage. It changes randomly, and comes to dominate the population when natural selection makes the change beneficial (which is, in turn, a function of environment, an environment which includes not only the physical environment, but the social environment, the chemical environment within the cell, including the other genes within the cell).

But mutations that are advantageous happen all the time, a number of which have been well-documented.

In addition, the fact that humans and chimpanzees have a common ancestor is not an assumption. It's a proven fact. The evidence is written all over our respective DNA.

 

[Chalnoth]

You do know that it results in a smaller brain right, how is that a selective advantage?

A specific mutation in the microcephalin gene causes abnormally small brain size. The gene itself regulates brain size, and is quite beneficial.
http://hmg.oxfordjournals.org/cgi/content/abstract/13/11/1131

 

[birdan]

-the microcephalin gene. A variant arose sometime between 14,000 and 60,000 years ago.

You do know that it results in a smaller brain right, how is that a selective advantage?

The microcephalin gene is part of the human genome. Everybody has this gene. All primates have a version of this gene. You are confusing microcephaly (an abnormal condition caused by a truncated mutation of this gene) with the gene itself. Comparing the human version of this gene to other primates finds 22 substitutions in the gene, resulting in 15 amino acids differences, with the most recent variation occurring 14,000 to 60,000 years ago. These variations are strongly suspected as being a primary driving force in the increase in brain size of humans over other primates.

 

[NASAg03]

the evolution logic is circular. it's a self-sustaining theory used to show that there doesn't NEED to be a god, and as such, they don't believe god exists.

evos make presumptions about the "naturally selective environment" that can't be proven. they state the environment dramatically changed over a period of 5 myr vs. 100 myr, which allowed chance mutations to dramatically change the primate genone and form humans.

evo circular logic:

1. environmental changes 2 mya naturally selected beneficial chance mutations in DNA, resulting in dramatic changes (18 over 2 million years) to a conservative gene (2 changes over 130 million years).

2. chance mutations captured in a conservative gene prove there were significant changes 2 mya.

 

[Chalnoth]

No, evolution is not circular, because it holds itself to the requirement that it describes the results of experiments which test reality.

 

[mark kennedy]

It doesn't change just because it would be an advantage. It changes randomly, and comes to dominate the population when natural selection makes the change beneficial (which is, in turn, a function of environment, an environment which includes not only the physical environment, but the social environment, the chemical environment within the cell, including the other genes within the cell).

That is exactly the problem with the HAR1 gene, random mutations are no explanation at all. We are talking about 18 nucleotides being substituted in a gene that has only say two substitutions in 310 million years. What you are missing is the distinction between a conserved and a transposable element.

But mutations that are advantageous happen all the time, a number of which have been well-documented.

They do? Take a look at this, it's a lists of well documented effects from mutations:

http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chooser.shtml

Click on any chromosome and you will get a list of the harmfull effects of mutations. So why didn't the Human Genome Project produce a simular list of beneficial effects? Because they are so rare and marginal in their effect there was no basis for such a list, that's why!

In addition, the fact that humans and chimpanzees have a common ancestor is not an assumption. It's a proven fact. The evidence is written all over our respective DNA.

No it's not a proven fact, it's a presumed fact that is unfalsifiable and as such does not qualify as a law of science, a theory or even an hypothesis. It's a myth and the inability to identify a genetic mechanism for this kind of an alteration speaks volumes for the power of an a priori assumption to blind peoples perceptions.

The laws of inheritance recognize a limit beyond which one species cannot change from one species into an altogether different kind. Evolution as natural history begs the question of a real world cause on it's hands and knees.

 

[mark kennedy]

the evolution logic is circular. it's a self-sustaining theory used to show that there doesn't NEED to be a god, and as such, they don't believe god exists.

Evolution as science is the change of alleles in populations over time. The real question is how many changes can be explained by known natural mechanisms. What they do is take something that is observed over days, weeks, years or in some cases decades. Then they project it over millions of years using convolution statistics to make it plausable.

evos make presumptions about the "naturally selective environment" that can't be proven. they state the environment dramatically changed over a period of 5 myr vs. 100 myr, which allowed chance mutations to dramatically change the primate genone and form humans.

Natural selection explains a lot about how harmfull mutations are eliminated. It does not rewrite the genetic code which is exactly what would have had to happen. Natural selection is nothing more then the death of the less fit, it produces absolutly nothing. They have the effect before the cause because the cause is allready presumed.

evo circular logic:

1. environmental changes 2 mya naturally selected beneficial chance mutations in DNA, resulting in dramatic changes (18 over 2 million years) to a conservative gene (2 changes over 130 million years).

2. chance mutations captured in a conservative gene prove there were significant changes 2 mya.

If it's a simularity then its and inherited trait, if there is a difference then it is an adaptation. Notice they never ask the real question of whether or not the single common ancestor model can be universally applied. They desperatly don't want you to know that the differences between apes and humans are far larger then we have been told. Now with comparitive genomics the truth is slowly coming out, random mutations does not explain the accelerated evolution of human lineages from that of apes.

Grace and peace,
Mark

 

[Chalnoth]

That is exactly the problem with the HAR1 gene, random mutations are no explanation at all. We are talking about 18 nucleotides being substituted in a gene that has only say two substitutions in 310 million years. What you are missing is the distinction between a conserved and a transposable element.

Only two substitutions that have spread throughout the population, you mean. This doesn't say anything about the mutation rate of the gene: it says something about the natural selection that the gene underwent in those organisms.

Obviously something about the natural selection changed in humans to allow this gene to evolve quickly. Its evolution is well within the mutation rate of humans (~175 errors per generation, out of ~3 billion base pairs).

What changed? Well, it could have been cultural, as in strong pressure on group members who have more intelligence. It could have been genetic: some of the mutations might have been detrimental if gene X wasn't there. I'm not sure what the people working directly in the field are saying, but I bet they have better ideas about it than this.

They do? Take a look at this, it's a lists of well documented effects from mutations:

http://www.ornl.gov/sci/techresources/Human_Genome/posters/chromosome/chooser.shtml

Click on any chromosome and you will get a list of the harmfull effects of mutations. So why didn't the Human Genome Project produce a simular list of beneficial effects? Because they are so rare and marginal in their effect there was no basis for such a list, that's why!

This just says that beneficial mutations are rare. Here are a few examples, after a quick bit of Googling:
http://www.gate.net/~rwms/EvoHumBenMutations.html
But it doesn't really matter that benficial mutations are rare: once they occur, they quickly spread through a population experiencing strong natural selection.

No it's not a proven fact, it's a presumed fact that is unfalsifiable and as such does not qualify as a law of science, a theory or even an hypothesis. It's a myth and the inability to identify a genetic mechanism for this kind of an alteration speaks volumes for the power of an a priori assumption to blind peoples perceptions.

Of course it's falsifiable, but I'll explain the evidence that proves beyond any reasonable shadow of a doubt that we did come from the same ancestor.

One type of mutation involves a virus inserting itself into a cell's DNA in order to use that cell to reproduce itself (destroying the cell). Sometimes, the virus undergoes the mutation that prevents the insertion from working properly: the cell survives, and the virus' code remains in the cell's DNA. Every once in a great while, the cell infected in this way is a sex cell that later ends up entering the genome of the offspring of this creature. If this mutation is not damaging (most mutations are neutral, after all), then this retrovirus insertion acts as a genetic marker: a specific piece of DNA at a specific place in the genome. Given the rarity of this type of insertion, it becomes a very clear indication of common descent.

We have detected some such retrovirus insertions that are in common between chimps and humans:
http://www.talkorigins.org/faqs/comdesc/section4.html#retroviruses

Common descent could be immediately falsified in the same way using this technique: one does not expect the retrovirus insertions that we see in humans, but are absent in other apes, to ever occur in any other animal. The probabilities are just absolutely astronomical against such an occurrence that it would be a clear falsification.

 

[mark kennedy]

No, evolution is not circular, because it holds itself to the requirement that it describes the results of experiments which test reality.

You are confusing evolution as science with evolution as natural history. You have completly ignored the evidence presented in this thread concerning the HAR1 gene. You keep chanting natural selection and random mutations but neither of these are any kind of an explanation at all.

What they would have expected is 1 or 0 substitutions, what they found was 18. The researchers said that out right, they did not beat around the bush. Your talking in circles around an evident and obvious fact, this gene is uniquely human and naturalistic causes for it do not exist.

Still you insist on your a priori assumption as a self-evident fact, regardless of the evidence and in this case, in spite of it.

 

[Chalnoth]

You are confusing evolution as science with evolution as natural history. You have completly ignored the evidence presented in this thread concerning the HAR1 gene. You keep chanting natural selection and random mutations but neither of these are any kind of an explanation at all.

Of course I do. Because the numbers make sense. Fast evolution of the HAR1 gene is no problem at all, provided the environment and natural selection are right. It is interesting that this gene evolved so quickly in humans, but so little in the other species talked about. But it isn't a refutation of evolution.

Evolution, after all, does not predict that evolution must progress along the same path in all organisms. In fact, it predicts that every organism's evolutionary path will be distinct. So not only is this not a refutation of evolution, I would expect it. I'd be willing to bet, for example, that if we looked hard enough we could find some other gene sequence that evolved as quickly in birds (likely relating to the formation of wings and/or feathers), but has stayed the same in their common ancestors that did not become birds.

P.S. Please respond to my previous post before tackling this one. I think it's got a lot more meat to it.

 

[mark kennedy]

Only two substitutions that have spread throughout the population, you mean. This doesn't say anything about the mutation rate of the gene: it says something about the natural selection that the gene underwent in those organisms.

Only two substitutions have spread through countless populations in 310 million years is what I mean. Like I keep trying to tell you, this would be an extraordinary change if were even possible. You are leaving out the only other viable alternative, two seperate lineages fully formed.

Obviously something about the natural selection changed in humans to allow this gene to evolve quickly. Its evolution is well within the mutation rate of humans (~175 errors per generation, out of ~3 billion base pairs).

No it's not well within the range because it is a highly conserved region. Show me one single beneficial effect from a mutation that is expressed in the brain. As many times as I have asked this question I have yet to get a single example.

What changed? Well, it could have been cultural, as in strong pressure on group members who have more intelligence. It could have been genetic: some of the mutations might have been detrimental if gene X wasn't there. I'm not sure what the people working directly in the field are saying, but I bet they have better ideas about it than this.

You sure love to talk in circles around the evidence don't you? More intelligence is allways a benefit but natural selection can only act on what is allready there. Let me share with you what people working in the field are saying:

The sophistication of the human brain is not simply the result of steady evolution, according to new research. Instead, humans are truly privileged animals with brains that have developed in a type of extraordinarily fast evolution that is unique to the species.

"Simply put, evolution has been working very hard to produce us humans," said Bruce Lahn, an assistant professor of human genetics at the University of Chicago and an investigator at the Howard Hughes Medical Institute.

"Our study offers the first genetic evidence that humans occupy a unique position in the tree of life...

"We've proven that there is a big distinction," Prof Lahn said. "Human evolution is, in fact, a privileged process because it involves a large number of mutations in a large number of genes.

"To accomplish so much in so little evolutionary time - a few tens of millions of years - requires a selective process that is perhaps categorically different from the typical processes of acquiring new biological traits."

"The making of the large human brain is not just the neurological equivalent of making a large antler. Rather, it required a level of selection that's unprecedented."

http://cogweb.ucla.edu/Abstracts/Dorus_04.html

This just says that beneficial mutations are rare. Here are a few examples, after a quick bit of Googling:
http://www.gate.net/~rwms/EvoHumBenMutations.html
But it doesn't really matter that benficial mutations are rare: once they occur, they quickly spread through a population experiencing strong natural selection.

Sure they do and the key here is, once they happen. Most mutations do nothing at all, the majority of the balance are mostly deleterious (harmfull). A very few may be beneficial for a time but usually are marginal in their effect.

Of course it's falsifiable, but I'll explain the evidence that proves beyond any reasonable shadow of a doubt that we did come from the same ancestor.

No you did not, you did a google search and kept chanting random mutations and natural selection. The actual evidence this thread is supposed to be discussing has been ignored both by you and the other posters. You have yet to explain how it is possible for such a highly conserved gene to be changed on this level. The human brain is unique and the more you look at the genes involved the greater the differences between humans and chimpanzees you see:

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.

http://www.christianforums.com/showpost.php?p=19911383&postcount=39

The retrovirus is not only off-topic, it is irrelevant. We are talking about a specific gene and the general subject of the evolution of the human brain. None of the evidence you seem to think is so conclusive proves this gene could evolve, let alone that it did.

Now if you want to make an honest effort to understand what the problem is here then I'm happy to discuss this at any length, in as much as I am able. They are finally beggining to unravel the genetic code and finding that it would have taken an unprecedented acceleration of the evolution of human genes related to the expansion of the human brain.

"A bigger, more complex brain may have advantages over a small brain in terms of computing power, but brain expansion has costs. For one thing, a big brain is a metabolic drain on our bodies. Indeed, some people argue that, because the brain is one of the most metabolically expensive tissues in our body, our brains could only have expanded in response to an improved diet. Another cost that goes along with a big brain is the need to reorganize its wiring. “As brain size increases, several problems are created”, explains systems neurobiologist Jon Kaas (Vanderbilt University, Nashville, Tennessee, United States). “The most serious is the increased time it takes to get information from one place to another.” (Molecular Insights into Human Brain Evolution, Jane Bradbury)

Natural selection does not produce bigger brains, it preserves favorable traits. Random mutations cannot even come close to explaining this and you keep insisting that they do. Why? Because no one knows how this is possible but we are all supposed to assume it is anyway. I'm no buying it.

 

[rmwilliamsll]

Show me one single beneficial effect from a mutation that is expressed in the brain. As many times as I have asked this question I have yet to get a single example.


The problem is how we find mutations. Up until just recently the only way to screen large numbers of people looking for alleles was to look at blood proteins and then look at the DNA underlying them.

We find almost all alleles at specific loci because of disease processes. That does not mean that there aren't other alleles at those loci nor does it mean that all people have the same allele at all the rest of the genes, it is a artifact of how we look at genetics.

Now this is changing as dna sequencers get cheaper and more wide spread. It is changing as projects like that in Iceland by deCODE Genetics of Reykjavik take hold and begin to produce data.

One of the big problems is that people see the money value of what they are doing and lots of these databases are pay for, lots of the sequences will be patented and other ways of monetizing the information. This will keep a lot of it off the net where types like us can learn about it.


However, there are fascinating clues that the brain is continuing to evolve.

just following the links in this is a good education on the issues.
http://www.futurepundit.com/archives/cat_brain_evolution.html

from: http://biology.plosjournals.org/perlserv/?request=get-document&doi=10.1371/journal.pbio.0040072

Recent articles have proposed that genes involved in brain development and function may have been important targets of selection in recent human evolution [8,9]. While we do not find evidence for selection in the two genes reported in those studies (MCPH1 and ASPM), we do find signals in two other microcephaly genes, namely, CDK5RAP2 in Yoruba, and CENPJ in Europeans and East Asians [46]. Though there is not an overall enrichment for neurological genes in our gene ontology analysis, several other important brain genes also have signals of selection, including the primary inhibitory neurotransmitter GABRA4, an Alzheimer's susceptibility gene PSEN1, and SYT1 in Yoruba; the serotonin transporter SLC6A4 in Europeans and East Asians; and the dystrophin binding gene SNTG1 in all populations.

http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=16151010&dopt=Abstract
http://www.ncbi.nlm.nih.gov/entrez/...ve&db=PubMed&list_uids=16151009&dopt=Abstract

http://www.vdare.com/Sailer/060101_economist.htm

here is an excellent review paper on the whole topic:
http://www.pnas.org/cgi/reprint/0509691102v1

here's one on PDYN
http://www.dukenews.duke.edu/2005/12/wrayplos.html


there are lots of information on the issue of evidence for recent human brain evolution including mutations that are known to do benefical things.

 

[Chalnoth]

Only two substitutions have spread through countless populations in 310 million years is what I mean. Like I keep trying to tell you, this would be an extraordinary change if were even possible. You are leaving out the only other viable alternative, two seperate lineages fully formed.

No it's not well within the range because it is a highly conserved region. Show me one single beneficial effect from a mutation that is expressed in the brain. As many times as I have asked this question I have yet to get a single example.

As I keep trying to say, merely stating that it is a "highly conserved region" without understanding why it is a highly conserved region is pointless. Transcription errors, for instance, will be almost independent of location on the DNA strand. Many transcription error mutations would have happened in any gene over a span of 301 million years. The only possible thing that one might use to explain the conservation of that gene is that natural selection prevented it from changing.

Sure they do and the key here is, once they happen. Most mutations do nothing at all, the majority of the balance are mostly deleterious (harmfull). A very few may be beneficial for a time but usually are marginal in their effect.

But this doesn't matter, because natural selection ensures it is only those that are beneficial are extended throughout a population. But since it is natural selection that decides whether or not a mutation is beneficial, for how long a mutation is beneficial depends entirely upon the environment. For example, you're probably thinking about the mutations that result in antibiotic resistance in bacteria, mutations that cease to be beneficial once the antibiotic is removed.

But take another example: the mutation responsible for sickle cell anemia. This mutation makes those affected resistant to malaria. Thus the mutation is beneficial in any area where malaria is a problem, but detrimental in any area where malaria is not a problem. Thus the gene in question has spread rapidly in those areas where malaria is a problem.

I see the progression of the HAR1 gene much in the same way: our ancestors, at one point, experienced some environmental, social, or genetic factors that caused a strong amount of selection in this gene. The ancestors of the chicken experienced different circumstances, circumstances that strongly selected against the basically inevitable negative side effects of single mutations in the HAR1 gene.

No you did not, you did a google search and kept chanting random mutations and natural selection. The actual evidence this thread is supposed to be discussing has been ignored both by you and the other posters. You have yet to explain how it is possible for such a highly conserved gene to be changed on this level. The human brain is unique and the more you look at the genes involved the greater the differences between humans and chimpanzees you see:

But we have proof that humans are descended from chimps through these retrovirus insertion markers! We therefore need to understand how we descended from apes, not question whether it happened at all. The only possible conclusion one can draw if one accepts your arguments is that human evolution was directed. But I'm not willing to give up that easily. We could understand so much more about how the world works by asking how it might have occurred naturally than just giving up and saying, "God did it." (Not that I'm working in this field, but the same issues arise in Cosmology).