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Author Topic:   Genetics and Human Brain Evolution
mick
Member (Idle past 4986 days)
Posts: 913
Joined: 02-17-2005


Message 46 of 157 (359579)
10-29-2006 1:00 AM
Reply to: Message 39 by eggasai
10-28-2006 4:45 PM


Re: some data and arguments on brain sizes in primates
eggasai writes:
The trend in the early hominids suggests to me that the trend in ape lineages was a decrease in absolute brain size
A plot of absolute cranial capacity over time, data drawn from every hominin skull found prior to 2000, shows precisely the opposite. Whether you consider these skulls to be part of the genus Homo or part of another extinct group of apes, there is no decrease over time in absolute cranial volume.
Source
eggasai writes:
Every ape skull dug up in Africa from prehistory is automatically put in human lineage
No, the skulls are placed in the "family tree" based on phylogenetic analysis of hundreds of morphological characteristics. These characteristics are strongly indicative of a greater affinity with Homo than with Pan or Gorilla. It's not a conspiracy or laziness - the shape of the tree is a mathematical result, it is not just drawn by hand from the imagination. You might make a valid argument that cladistic methods are inappropriate, but every proposed cladistic algorithm reaches a very similar conclusion, so you would have to propose a new algorithm.
The species in the cladogram below that are labelled "Homo" are so simply because they cluster with Homo sapiens. But it doesn't matter whether you call them "Homo" or just "extinct apes", their biological relationship to humans is specified by the shape of the tree and not by the names we give to them.
Source, based on 198 craniodental characteristics
eggasai writes:
There is no genuine absolute brain/body size ratios
That's a good point, but since we don't have any bodies with tissues we have little choice but to infer body mass if we want to talk about these issues. A variety of hominid and ape body mass models can be used; they are able to predict (imprecisely but reasonably) the body mass of extant apes; and they all give pretty similar results in terms of the general trend in encephalization. One might also calculate an encephalization quotient based on the correlation between cranial capacity and some other measurable skeletal variable, but I can't find an example of that having been done and I foresee difficulties because craniodental characters will be functionally correlated as well as correlated by body mass allometry.
eggasai writes:
The austrophithecines average slightly above that of a modern ape. The overall brain size did not double from the Austropithecines to the habilines. Homo habilis had a cranial capacity below 600cc while the austropithecines has a cranial capacity about 400cc. The cranial capacity does not actually make a signifigant jump until Homo habilis where it goes from under 600cc to close to 1000cc.
You are still using absolute brain volumes, and this is statistically unsound because you are ignoring a known fact that brain size is a covariate of body size. Consider the body mass and endocranial volume of two Homo habilis individuals and the mean values for a few other apes.


Species Body mass (g) Endocranial volume (cm3)

Male Orangutan 87700 393.1
Female Orangutan 37800 341.2
Male Gorilla 169500 537.4
Female Gorilla 71500 441.4
Male Chimp 60000 406.5
Female Chimp 47400 370.6
Female Bonobo 33200 295.5
Female H habilis 1 30286 594
Female H habilis 2 34883 509
Source
Although the brain volume of female Homo habilis is of the same order of magnitude as the male Gorilla, the habilis body mass is about five times smaller. Similarly, although the body mass of female Homo habilis is of the same order of magnitude as the female Bonobo, the habilis brain volume is half as large again. What does this signify? Each of the species listed here has a limited supply of resources that it can invest in its own growth and development. Homo habilis is clearly investing an enormously larger proportion of resources than the male gorilla in brain growth as opposed to the growth of the body. It is this difference in the allocation of resources to the brain versus elsewhere that is of evolutionary interest. The absolute values are of little interest because natural selection is acting on the trade-off over allocation of limited resources, not on absolute magnitude. Sure, big animals have access to greater resources and can grow larger arms, legs, fingers and brains. But such an increase in absolute brain growth tells us little about the evolution and energetics of brain development. The fact that an African male human being has an absolutely larger brain than an Asian female, for example, does not tell us much of evolutionary interest, since African males simply tend to be larger than Asian females. Once you correct for size, the two groups are seen to invest rather similar levels of their energetic resources into brain development.
If you think that correcting for body mass is irrelevant, why do you bring up the hominids rather than the dogs? They provide a far more striking example of rapid change in absolute brain size, with major differences such as between the brain size of a chihuahua and a great dane occurring over a few thousand years. Are such differences in dog brain size also impossible to account for with evolutionary theory? I doubt you'd even find a single creationist to agree with that.
Cheers!
Mick
Edited by mick, : typo

This message is a reply to:
 Message 39 by eggasai, posted 10-28-2006 4:45 PM eggasai has replied

Replies to this message:
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Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 47 of 157 (359592)
10-29-2006 4:40 AM
Reply to: Message 44 by crashfrog
10-28-2006 8:09 PM


Re: Fundamental Biology Question
I think Crash has done a great job of representing the 'reality based' approach to the central dogma. In case Eggasai once again completely fails to engage the substance of a c;ear contradiction of his fantasy molecular biology approach I'd like to suggest the Flash animations DNA transcription and RNA translation at communicating at an unknown rate as a nice visual presentation of the same processes.
TTFN,
WK

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Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 48 of 157 (359672)
10-29-2006 1:55 PM
Reply to: Message 42 by eggasai
10-28-2006 7:07 PM


Re: Maybe I should stay out of this.
The Talk Origins shelf of skulls gives the illusion of a gradual anagenesis of the human skull. Homo habils had a cranial capacity just over 500cc
Rudolphensis is 750+ cc.
... while the Austropithecines are thought to have averaged above 400cc.
Averaged, eh?
What size was the largest?
The period from at least 5 mya until under 2 mya represents a prolonged period of stasis with about a 200cc variance not counting dimorphic variables. Homo habilis was most likely contemporary with Turkana Boy or only seperated by a couple of hundred thousands years.
Habilis is also contemporary with australopithicenes. So are some specimens of erectus. And we are contemporary with monkeys. What's your point?
Turkana Boy weighs in at a cranial capacity above 900cc
880 cc.
and Homo erectus cranial capacity remains static for at least 1 million years.
Courtesy of the Panda's Thumb weblog.
Now, if you would like to take a walk through the shelf of skulls I would be delighted to debunk this optical illusion with substantive details. By the way, Homo rudolfensis was originally dated 3 million years old and only moved because Homo habilis was 200cc smaller. The dates assigned are obviously bogus...
Saying this won't make it so. If you have evidence that any of the dates are "bogus", please produce it.
On the contrary, I have the Chimpanzee Genome Consortioums conclusion that natural selection was not a factor in the evolution of humans from the last common ancestor of chimps and humans.
You have no such thing.
I have the selective coefficients from the divergance between human and chimpanzee genomes. I have the comparative anatomy of contemporary chimanzee and human morphological traits to use as a based line. Finally I have the divergance of the respective genomes and the observed mutation rate for hominids, the fixation rate and the deleterious effects of mutations on protein coding and functional genes.
And yet you have presented no quantitative reasoning.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.

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 Message 42 by eggasai, posted 10-28-2006 7:07 PM eggasai has replied

Replies to this message:
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tatiana 
Inactive Member


Message 49 of 157 (359674)
10-29-2006 2:22 PM
Reply to: Message 3 by New Cat's Eye
08-19-2005 1:23 AM


Warning - 419 scam i need your help
my name is tatiana kenneth, i saw your profil and need your assistance.pls contact me on this email address tatianakenn1@yahoo.com
WARNING: To anybody who received email from this person - This is a classic 419 scam operation, sometimes known as Nigerian Scam, though this one appears to come from the Ivory Coast. DO NOT CORRESPOND with this banned member.
Edited by AdminNWR, : Spam/scam warning

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eggasai
Inactive Member


Message 50 of 157 (359694)
10-29-2006 5:27 PM
Reply to: Message 46 by mick
10-29-2006 1:00 AM


Re: some data and arguments on brain sizes in primates
quote:
A plot of absolute cranial capacity over time, data drawn from every hominin skull found prior to 2000, shows precisely the opposite. Whether you consider these skulls to be part of the genus Homo or part of another extinct group of apes, there is no decrease over time in absolute cranial volume.
Homo rudolfensis KNM-ER 1470 was originally dated 3 million years old which would make it older then the australopithecines. It had to be moved up a million years because it didn't fit into the anagenesis of Darwinian naturalistic a priori assumptions.
quote:
No, the skulls are placed in the "family tree" based on phylogenetic analysis of hundreds of morphological characteristics.
They are placed in the chart in such a way as to give the illusion of anagenesis. What you are calling a phylogenetic analysis is really Darwin's tree of life revisted. It is an a priori assumption that has no genuine frame of referance.
quote:
eggasai writes:
There is no genuine absolute brain/body size ratios
That's a good point, but since we don't have any bodies with tissues we have little choice but to infer body mass if we want to talk about these issues. A variety of hominid and ape body mass models can be used; they are able to predict (imprecisely but reasonably) the body mass of extant apes; and they all give pretty similar results in terms of the general trend in encephalization. One might also calculate an encephalization quotient based on the correlation between cranial capacity and some other measurable skeletal variable, but I can't find an example of that having been done and I foresee difficulties because craniodental characters will be functionally correlated as well as correlated by body mass allometry.
You are trying to use a very precise measurement and apply it to skulls that are often crushed, fragmented and dated using highly subjective criteria. Cranial capacity represents a cerebral rubicon that marks a clear line of demarkation in the transition from ape to humans. The genetic basis for such a morphological innocation simply does not exist.
"We’ve proven that there is a big distinction. Human evolution is, in fact, a privileged process because it involves a large number of mutations in a large number of genes,” Lahn said.
“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.”
Generally speaking, the higher up the evolutionary tree, the bigger and more complex the brain becomes (after scaling to body size). But this moderate trend became a huge leap during human evolution. The human brain is exceptionally larger and more complex than the brains of nonhuman primates, including man’s closest relative, the chimpanzee.
One way to study molecular evolution is to examine changes of when and where proteins are expressed in the body. “But there are many challenges to studying the evolution of protein expression. Instead, we chose to track structural changes in proteins,” said graduate student Eric Vallender, lead author of the article along with former graduate student Steve Dorus, who both work with Lahn.
The researchers examined the DNA of 214 genes involved in brain development and function in four species: humans, macaques (an Old World monkey), rats and mice. (Primates split from rodents about 80 million years ago; humans split from macaques 20 million to 25 million years ago; and rats split from mice 16 million to 23 million years ago.)"
http://chronicle.uchicago.edu/050106/lahn.shtml
quote:
You are still using absolute brain volumes, and this is statistically unsound because you are ignoring a known fact that brain size is a covariate of body size. Consider the body mass and endocranial volume of two Homo habilis individuals and the mean values for a few other apes.
No I'm not, I'm making a very specific inferance based on what science is telling us about this supposed transitional. The brain would have had to triple in size in about 1.5 million years from Homo habilis 510cc and modern humans 1350cc. This become increasingly ridiculas when you look at the actual genes involved. Do you realize that most of the neural genes would require in-frame indels of considerable length. Brain genes are amoung the most highly conserved genes in the human body, a close second would be the liver which would have underwent intense adaptive evolution as well. Random mutations plus natural selection are obviously not going to get you where there. Relaxed funtional constrait does not make any sense because of the deleterious effects. Then there is the fact that these would have to be germline mutations during the cleavage stage and it is here that mutations are least likely to occur.
Now you can use all the scattergrams and tree like charts you like. The genetic basis such such a morphological giant leap does not exist except in the mind of Darwinians.
quote:
Although the brain volume of female Homo habilis is of the same order of magnitude as the male Gorilla, the habilis body mass is about five times smaller. Similarly, although the body mass of female Homo habilis is of the same order of magnitude as the female Bonobo, the habilis brain volume is half as large again. What does this signify?
What you are doing here is pouring the concrete before the frame is ready. EQ is fine for making precise measurements but we really don't have those from prehistory, for one thing the dates are highly subjective. That said, do you really think it makes sense to compare Homo habilis (actually an austropithcine if you mean OH62) to a gorilla? Why don't you do you little formula for a chimpanzee? I think you will find that Homo habils is just a little bigger.
quote:
It is this difference in the allocation of resources to the brain versus elsewhere that is of evolutionary interest. The absolute values are of little interest because natural selection is acting on the trade-off over allocation of limited resources, not on absolute magnitude. Sure, big animals have access to greater resources and can grow larger arms, legs, fingers and brains. But such an increase in absolute brain growth tells us little about the evolution and energetics of brain development.
You can't compare the adaptation of a limb to the complete overhaul of neural genes, it has no rational basis:
"“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,” Lahn said. “Our study offers the first genetic evidence that humans occupy a unique position in the tree of life. Simply put, evolution has been working very hard to produce us humans.” " (from the article linked above)
quote:
The absolute values are of little interest because natural selection is acting on the trade-off over allocation of limited resources, not on absolute magnitude.
The absolute values are of paramount importance whether they interest you or not. They are crucial because your explanation of natural selection would not have been a big factor.
"Although it is more difficult to quantify the expected contributions of selection in the ancestral population, it is clear that the effects would have to be very strong to explain the large-scale variation observed across mammalian genomes. There is tentative evidence from in-depth analysis of divergence and diversity that natural selection is not the major contributor to the large-scale patterns of genetic variability in humans." (Chimpanzee Genome Consortium, Nature 2005)
Charles Darwin when he wrote On the Origin of Species proposed that natural selection was the primary mechanism for adaptive evolution. In this day and age it's the first thing the evolutionists use to explain a major mophological adaptation. How did we get here? Darwin's On the Origin of Species is just one long arguement against 'special creation'. It's not a genetic mechanism, it's rethoric used as a dialectical tool meant to seperate people from belief in 'special creation', nothing more.
Want to show me I'm wrong, no problem. Let's take a walk through that actual scientific research. We can look at the Chimpanzee Genome paper, some of Bruce Lahn's work and the allometry of Asian Homo erectus skulls compared to modern Chinese. I'm telling you before we start, the transtion from Homo habilis to Homo erectus didn't happen and the evidence is telling us exactly that.
Edited by eggasai, : transcript error having a deleterious effect on my post

This message is a reply to:
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Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 51 of 157 (359698)
10-29-2006 5:50 PM
Reply to: Message 50 by eggasai
10-29-2006 5:27 PM


Re: some data and arguments on brain sizes in primates
Homo rudolfensis KNM-ER 1470 was originally dated 3 million years old which would make it older then the australopithecines. It had to be moved up a million years because it didn't fit into the anagenesis of Darwinian naturalistic a priori assumptions.
This is not true, which is why you are completely unable to substantiate it. A mere glance at the graph would tell you that that would still leave australopithicines earlier than rudolphensis; and a moment's common sense would have told you that the scientist who proposed the 3 mya date was a Darwinian.
They are placed in the chart in such a way as to give the illusion of anagenesis. What you are calling a phylogenetic analysis is really Darwin's tree of life revisted. It is an a priori assumption that has no genuine frame of referance.
This is not true, which is why you are completely unable to substantiate it. You are evidently entirely ignorant of the methods used --- why don't you go and find out about them?
You are trying to use a very precise measurement and apply it to skulls that are often crushed, fragmented and dated using highly subjective criteria.
Make up your mind. A moment ago you were arguing that the data on cranial capacity supported you. Now you are attempting to rubbish the data.
Cranial capacity represents a cerebral rubicon that marks a clear line of demarkation in the transition from ape to humans.
Please point it out on the graph.
The genetic basis for such a morphological innocation simply does not exist.
This is not true: we know of many genetic differences between humans and the other apes; we know that these differences affect brain proteins. See, for example, the paper you quote below.
"We’ve proven that there is a big distinction. Human evolution is, in fact, a privileged process because it involves a large number of mutations in a large number of genes,” Lahn said.
“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.”
Yes. And?
Let's hear a bit more from Lahn et al. From the same artcle, had you read it.
To further investigate the role of selection on brain development, the researchers compared the evolutionary rate of brain-related genes against a control group of 95 genes, which are involved in basic functions necessary for each cell in the body to survive.
“If there is something inherently different about humans in the evolution of their genes, not related to selection, the control genes should reveal it, too. These basic, conserved genes are the last to change,” Vallender said.
The control genes looked the same, indicating there was not an excess of changes in these genes during human evolution. This provides a sharp contrast to the tremendous excess of changes in the brain-related genes.
Generally speaking, the higher up the evolutionary tree, the bigger and more complex the brain becomes (after scaling to body size). But this moderate trend became a huge leap during human evolution.
Where is the "huge leap"?
The human brain is exceptionally larger and more complex than the brains of nonhuman primates, including man’s closest relative, the chimpanzee.
But not much larger than H. erectus.
Now you can use all the scattergrams and tree like charts you like. The genetic basis such such a morphological giant leap does not exist except in the mind of Darwinians.
Actually, the "giant morphological leap" exists only in the minds of creationists.
The absolute values are of paramount importance whether they interest you or not. They are crucial because your explanation of natural selection would not have been a big factor.
"Although it is more difficult to quantify the expected contributions of selection in the ancestral population, it is clear that the effects would have to be very strong to explain the large-scale variation observed across mammalian genomes. There is tentative evidence from in-depth analysis of divergence and diversity that natural selection is not the major contributor to the large-scale patterns of genetic variability in humans." (Chimpanzee Genome Consortium, Nature 2005)
You have misunderstood them completely. Most of the genetic differences between humans and chimps are of course the result of neutral drift. But the other biologists you have quoted have all said that selection must have been playing a very strong role when it comes to brain function.
How did we get here? Darwin's On the Origin of Species is just one long arguement against 'special creation'. It's not a genetic mechanism, it's rethoric used as a dialectical tool meant to seperate people from belief in 'special creation', nothing more.
This is not true, which is why you are completely unable to substantiate it. I know this because I have read the Origin Of Species. You should try it sometime, preferably before you next presume to lecture people on its contents.
Want to show me I'm wrong, no problem. Let's take a walk through that actual scientific research. We can look at the Chimpanzee Genome paper...
Yes. Start by reading that until you understand it.
I'm telling you before we start, the transtion from Homo habilis to Homo erectus didn't happen and the evidence is telling us exactly that.
Your claim being supported by ... what? Surely not those "skulls that are often crushed, fragmented and dated using highly subjective criteria"? 'Cos if so, then the graph clearly shows no great morphological leap. If, on the other hand, you are basing your opinion on something other than the actual fossil remains, I am at a loss to think what it could be.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.
Edited by Dr Adequate, : No reason given.

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 Message 50 by eggasai, posted 10-29-2006 5:27 PM eggasai has not replied

  
Wounded King
Member
Posts: 4149
From: Cincinnati, Ohio, USA
Joined: 04-09-2003


Message 52 of 157 (359699)
10-29-2006 5:59 PM
Reply to: Message 50 by eggasai
10-29-2006 5:27 PM


Re: some data and arguments on brain sizes in primates
This become increasingly ridiculas when you look at the actual genes involved. Do you realize that most of the neural genes would require in-frame indels of considerable length.
I doubt that anyone realises this since there is nothing to suggest that it is the case. Do you have any actual reference which suggests that the mutations would need to be in-frame indels, let alone of considerable length?
Brain genes are amoung the most highly conserved genes in the human body
This is a very strange way to think of things, it is more usual to talk of conservation with a particular group of organisms such as the mammals or vertebrates. Being conserved within the human body just suggests that they aren't likely candidates for somatic mutation. This also seems directly contradicted by a lot of the evidence you yourself have shown showing that many neural genes have been subject to mutation and in many cases apparently to very strong selection leading to many more changes than might be expected under neutral selection.
Random mutations plus natural selection are obviously not going to get you where there.
This only seems obvious to you, and you have yet to produce a scrap of reasoned argument why anyone should accept your contention.
Relaxed funtional constrait does not make any sense because of the deleterious effects.
You have produced no evidence to suggest that any of the difference between human genes and their highly conserved counterparts in other species have a deleterious effect. Your argument also seems to fail through basic logic. A relaxation of functional constraint by its very nature means that there are more possible non-deleterious mutations possible.
Then there is the fact that these would have to be germline mutations during the cleavage stage and it is here that mutations are least likely to occur.
What is this supposed to mean? Why should mutations occur during cleavage? I assume you mean cleavage during mitosis or meiosis rather than an embryonic cleavage stage but the reasoning behind your statement escapes me.
TTFN,
WK

This message is a reply to:
 Message 50 by eggasai, posted 10-29-2006 5:27 PM eggasai has replied

Replies to this message:
 Message 55 by eggasai, posted 10-29-2006 6:54 PM Wounded King has replied

  
eggasai
Inactive Member


Message 53 of 157 (359701)
10-29-2006 6:17 PM
Reply to: Message 48 by Dr Adequate
10-29-2006 1:55 PM


Re: Maybe I should stay out of this.
On the contrary, I have the Chimpanzee Genome Consortioums conclusion that natural selection was not a factor in the evolution of humans from the last common ancestor of chimps and humans.
quote:
You have no such thing.
"Although it is more difficult to quantify the expected contributions of selection in the ancestral population, it is clear that the effects would have to be very strong to explain the large-scale variation observed across mammalian genomes. There is tentative evidence from in-depth analysis of divergence and diversity that natural selection is not the major contributor to the large-scale patterns of genetic variability in humans." (Chimpanzee Genome Consortium, Nature 2005)
Maybe you should read my posts and the scientific literature a little more carfully.
Edited by eggasai, : Transcript error

This message is a reply to:
 Message 48 by Dr Adequate, posted 10-29-2006 1:55 PM Dr Adequate has replied

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Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 54 of 157 (359702)
10-29-2006 6:26 PM
Reply to: Message 53 by eggasai
10-29-2006 6:17 PM


Re: Maybe I should stay out of this.
Maybe you should read my posts and the scientific literature a little more carfully.
Funn-ee. Did you read a word of what you just quoted?
The Chimpanzee Genome Consortium say that there is little evidence that natural selection is the cause of genetic diversity in humans.
By what mental freak did you manage to read that as meaning that "natural selection was not a factor in the evolution of humans from the last common ancestor of chimps and humans"?
It's a complete non sequitur. To quote the late, great Thomas Ady: "Oh gallant! as the Wheel-Barrow goeth ramble the Ramble; so Peter Sherk owes me Five shillings."
---
If you had read the article about Lahn that you cited, you would have noticed that it is actually titled "Human cognitive abilities resulted from intense evolutionary selection, says Lahn". Didn't you even read the darn title?
Edited by Dr Adequate, : No reason given.

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eggasai
Inactive Member


Message 55 of 157 (359703)
10-29-2006 6:54 PM
Reply to: Message 52 by Wounded King
10-29-2006 5:59 PM


"natura non facit saltum"
"Taken together, gross structural changes affecting gene products are far more common than previously estimated (20.3% of the PTR22 proteins, as listed in Supplementary Tables 4 and 5)."
The International Chimpanzee Chromosome 22 Consortium, Nature 27 May 2004
These are inframe indels in protein coding genes, notice it's 20.3% of the ones on PTR22. Actually these are just differences in side by side comparision but when assuming a common ancestor it must have been an indel that produced it.
quote:
This is a very strange way to think of things, it is more usual to talk of conservation with a particular group of organisms such as the mammals or vertebrates. Being conserved within the human body just suggests that they aren't likely candidates for somatic mutation. This also seems directly contradicted by a lot of the evidence you yourself have shown showing that many neural genes have been subject to mutation and in many cases apparently to very strong selection leading to many more changes than might be expected under neutral selection.
What it contradicts is the a priori predictions of Darwinians who expected anagenesis progressions rather then a major overhaul of protein coding genes. That isn't near as astonishing as the inframe indels that would be required in the regulatory genes or the outliers, particularly the ones that are functionally biased in crucial neural development.
quote:
This only seems obvious to you, and you have yet to produce a scrap of reasoned argument why anyone should accept your contention.
It seems as obvious as it needs to if you are aquainted with the scientific literature on the subject. Why don't you google mutations and human neural genes or just read some of the papers I often quote, cite and link.
quote:
You have produced no evidence to suggest that any of the difference between human genes and their highly conserved counterparts in other species have a deleterious effect. Your argument also seems to fail through basic logic. A relaxation of functional constraint by its very nature means that there are more possible non-deleterious mutations possible.
The only times that relaxed functional constraint is obsered is rare instances where it improves the enzymes ability purge transcript errors. The only reason that the mutation rate is not 0 is because of the physiological costs of adaptation. Relaxed funtional constraint, 'by it's nature' runs the risk of severly deleterious effects due to an increase in the number of them. I fail to accept the logic you are using because...how can I say this nicely... it oversimplifies things way too much.
quote:
What is this supposed to mean? Why should mutations occur during cleavage? I assume you mean cleavage during mitosis or meiosis rather than an embryonic cleavage stage but the reasoning behind your statement escapes me.
"The diversity of the earliest stages of development, here illustrated strictly within the vertebrates, provides one of the strongest challenges to the neo-Darwinian conception of homology and macroevolution. Given the hierarchical, step-wise logic or "architecture" of animal development, early stages such as cleavage and gastrulation lay the groundwork for all that follows. Body plan structures in the adult, for example, trace their cellular lineage to these early stages. Thus, if macroevolution is going to occur, it must begin in early development. Yet it is precisely here, in early development, that organisms are least tolerant of mutations. Furthermore, the adult homologies shared by these vertebrates commence at remarkably different points (e.g., cleavage patterns). How then did these different starting points evolve from a common ancestor?"
http://www.arn.org/docs/odesign/od182/hobi182.htm

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AdminNosy
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Message 56 of 157 (359705)
10-29-2006 7:07 PM
Reply to: Message 54 by Dr Adequate
10-29-2006 6:26 PM


Caution Dr A
Please continue to exhibit patience. You are doing well even if it is challenging.
I have no complaint as yet with anyone. But it seems that there is a chance of posts moving across a line if the tiny little barbs continue.
Thanks.

This message is a reply to:
 Message 54 by Dr Adequate, posted 10-29-2006 6:26 PM Dr Adequate has replied

Replies to this message:
 Message 58 by Dr Adequate, posted 10-29-2006 7:26 PM AdminNosy has not replied

  
Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 57 of 157 (359707)
10-29-2006 7:11 PM
Reply to: Message 55 by eggasai
10-29-2006 6:54 PM


Re: "natura non facit saltum"
"Taken together, gross structural changes affecting gene products are far more common than previously estimated (20.3% of the PTR22 proteins, as listed in Supplementary Tables 4 and 5)."
The International Chimpanzee Chromosome 22 Consortium, Nature 27 May 2004
These are inframe indels in protein coding genes, notice it's 20.3% of the ones on PTR22. Actually these are just differences in side by side comparision but when assuming a common ancestor it must have been an indel that produced it.
Why do you mention this?
What it contradicts is the a priori predictions of Darwinians who expected anagenesis progressions rather then a major overhaul of protein coding genes.
I don't know what you think "anagenesis" means, but you're wrong. This makes this sentence singularly meaningless.
(1) Anagenesis is the evolution of one species from another without branching, as opposed to cladogenesis.
(2) There is absolutely nothing in the theory of evolution which requires evolution to be anagenetic: on the contrary.
(3) The question of whether a particular transition was anagenetic or cladogenetic has, obviously, absolutely damn-all to do with the question of whether "a major overhaul of protein coding genes" took place.
It seems as obvious as it needs to if you are aquainted with the scientific literature on the subject.
But you aren't. You've made one dreadful howler after another on the most basic facts of genetics, and are apparently unable to understand the papers you cite.
Why don't you google mutations and human neural genes or just read some of the papers I often quote, cite and link.
Why don't you read them, instead of merely quoting, citing, and linking them?
Heck, why don't you read a copy of Genetics For Dummies until you at least know what an amino acid is?
"How then did these different starting points evolve from a common ancestor?"
Natural selection.
Sheesh.
Another non-quantitative argument from incredulity. Just stick it next to all the others.

This message is a reply to:
 Message 55 by eggasai, posted 10-29-2006 6:54 PM eggasai has not replied

  
Dr Adequate
Member (Idle past 285 days)
Posts: 16113
Joined: 07-20-2006


Message 58 of 157 (359711)
10-29-2006 7:26 PM
Reply to: Message 56 by AdminNosy
10-29-2006 7:07 PM


Re: Caution Dr A
I shall try to take the edge off my tongue, since you ask it.

This message is a reply to:
 Message 56 by AdminNosy, posted 10-29-2006 7:07 PM AdminNosy has not replied

  
42
Inactive Member


Message 59 of 157 (359723)
10-29-2006 7:58 PM


There's nothing special about humans. They're just a bit more brainy than other hominids, who exhibited bipedalism, and in some cases lived in wooden huts. Who can say what Homo floresiensis may have achieved in terms of language, thought and technology if the world had not become so full of human tribes.

Human Evolution in 42 Steps

  
RAZD
Member (Idle past 1405 days)
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004


Message 60 of 157 (359738)
10-29-2006 9:54 PM
Reply to: Message 42 by eggasai
10-28-2006 7:07 PM


Maybe you should try logical arguments and the use of real evidence.
I would be delighted to debunk this optical illusion with substantive details.
Given that you have avoided such details to date that might be a refreshing change. You'll excuse me if I expect more misrepresentation, straw man arguments and arguments from incredulity.
What Talk Origins fails to clarify is that the human brain is three times that of a chimpanzee.
Repeated assertion of your personal incredulity and denial of evidence of this change in the fossil record does not make it any more valid than it was the first time. There is clear transition from B to N, and you have yet to deal with that issue.
By the way, Homo rudolfensis was originally dated 3 million years old and only moved because Homo habilis was 200cc smaller.
Care to substantiate that with the scientific paper that cites that exact thing? Or do we deal with another creationist misrepresentation site.
Everything from A to F is an ape, everything from G to you and me are humans. ... I say it's either ape or human,...
Given that human = ape that is not saying much is it?
If you want to say that some are Homo and others are pre Homo human ancestral apes (hominids) that is also no different than what the science people are saying eh? But you are still not dealing with D to N being Homo in classification. Nor is this dealing with the rest of the skeletal evidence in the fossil record, such as knees and hips that also show transition from ancestral hominid ape to modern human ape.
... and speciman catalogue ID.
Do you ever read the posts? Or do you not know what the catalogue ID's are\look like?
quote:
(B) Australopithecus africanus, STS 5, 2.6 My
(C) Australopithecus africanus, STS 71, 2.5 My
(D) Homo habilis, KNM-ER 1813, 1.9 My
(E) Homo habilis, OH24, 1.8 My
(F) Homo rudolfensis, KNM-ER 1470, 1.8 My
(G) Homo erectus, Dmanisi cranium D2700, 1.75 My
(H) Homo ergaster (early H. erectus), KNM-ER 3733, 1.75 My
Color yellow for emPHAsis.
Now we can ignore the neander skulls as evidence of direct ancestry, they are there as a side branch that also shows where they fit in the overall picture.
You do realize that the neander brains in the later specimens were bigger than those of Cro-Magnon, so absolute brain size is not necessarily a relation to brain {power\capacity\ability} eh?
... what is your criteria for determining it is a transitional?
The scientific one: that it shows evidence of features intermediate in form and development between the ancestor and the progeny.
... represents a prolonged period of stasis with about a 200cc variance ... remains static for at least 1 million years ...
So? You realize this being an example of "punk-eek" does not mean that the evolution between those stages does not still occur, yes? Just because you find it more incredulous does not mean it did not happen. Once again nature is not limited by your personal incredulity.
I am far from incredulous and I'm immune to these Darwinian rethorical devices.
LOL. Immune to logic has been apparent from your other posts.
Pointing out the invalid use of logical fallacies (like straw man and argument from incredulity) are not "Darwinian" nor "rethorical(sic) devices" - they are the basis of logical communication, using words and concepts in ways that can be validated by the structure of the arguments, built on evidence and reason rather than rejection any denial. They apply to philosophy as well as to sciences like astronomy, chemistry, physics, etcetera.
Finally I have the divergance of the respective genomes and the observed mutation rate for hominids, the fixation rate and the deleterious effects of mutations on protein coding and functional genes.
And you have failed to present your case that the rate of mutation could not have happened. You have failed to address the issue of sexual selection and the elements of human physiology that show evidence of being products of run-away sexual selection - including the size of the brain.
Just to refresh your memory, one of these markers of run-away sexual selection is a feature so developed in one direction that further development is increasingly lethal to the organisms that show such development.
The size of the human brain has reached the point where increased size is increasing lethal to both mother and fetus.
As far as the genetics of brain size goes, it is not just a matter of size per se, but where that size increases in the intermediate forms.
http://www.massey.ac.nz/~alock/hbook/brain.htm
quote:
With regard to brain reorganization, left-right cerebral hemispheric asymmetries exist in extant pongids and the australopithecines, but neither the pattern nor direction is as strongly developed as in modern or fossil Homo. KNM-ER 1470 shows a strong pattern that may be related to handedness and tool-use/manufacture. The degree of asymmetry appears to increase in later hominids.
The appearance of a more human-like third inferior frontal convolution provides another line of evidence about evolutionary reorganization of the brain. None of the australopithecine endocasts show this region preserved satisfactorily. There is a consensus among palaeoneurologists that the endocast of the specimen KNM-ER 1470 does show, however, a somewhat more complex and modern-human-like third inferior frontal convolution compared with those of pongids.
Note that specimen KNM-ER 1470 is in the above referenced chart as skull (F).
continuing:
quote:
Unfortunately, later hominid endocasts, including H. habilis and H. erectus through archaic H. sapiens to the present, seldom show the sulcal and gyral patterns faithfully. Thus nothing palaeoneurological can be said with confidence about possible changes with the emergence of anatomically modern H. sapiens. On the other hand, there is nothing striking about Neanderthal brain casts in comparison to more recent H. sapiens, except their slightly larger size, suggesting no significant evolutionary change thereon.
They say the evidence is not completely conclusive (scientific tentativity) but DO note that neanderthal did not have the brain regions develope in similar relationship to their size, thus we can conclude that SIZE is not related to BRAIN {power\capacity\ability}.
The issue is not brain size but {power\capacity\ability}. The selection is not for larger size - that is just an easy way to increase {power\capacity\ability} - but we also see that selection is still going on:
Science Mag Article: Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens (abstract):
quote:
The gene ASPM (abnormal spindle-like microcephaly associated) is a specific regulator of brain size, and its evolution in the lineage leading to Homo sapiens was driven by strong positive selection. Here, we show that one genetic variant of ASPM in humans arose merely about 5800 years ago and has since swept to high frequency under strong positive selection. These findings, especially the remarkably young age of the positively selected variant, suggest that the human brain is still undergoing rapid adaptive evolution.
Brain still evolving {power\capacity\ability} ...
There is also the issue of genetic 'errors in births that result in microencephaly:
PubMed: Evolutionary History of a Gene Controlling Brain Size (abstract)
quote:
One way to figure out which genes are involved in a physiological process is to analyze mutations in the genotype that generate an abnormal phenotype. Such efforts are easier in the relatively rare instance that one gene affects a single trait. Mutations in the ASPM gene cause microencephaly, a rare incurable disorder characterized by an abnormally small cerebral cortex. Since the microencephalic brain is about the same size as the early hominid brain, researchers hypothesized that ASPM”whose normal function is unclear”may have been a target of natural selection in the expansion of the primate cerebral cortex. Last year, researchers showed that selective pressure on the ASPM gene correlated with increased human brain size over the past few million years, when humans and chimps diverged from their common ancestor. Now, Vladimir Larionov and colleagues report that the selective pressure began even earlier”as far back as 7-8 million years ago, when gorillas, chimps, and humans shared a common ancestor.
color for emPHAsis.
So we have the issue of a single gene being damaged causing a result similar to early hominid skulls.
Thus it isn't necessary for ALL the brain gene modifications to relate to size, just to some selected aspect of brain performance ... {power\capacity\ability} ...
Enjoy.

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This message is a reply to:
 Message 42 by eggasai, posted 10-28-2006 7:07 PM eggasai has not replied

  
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