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Author Topic:   Human Brain Evolution Was a 'Special Event'
RAZD
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Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
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Message 46 of 65 (353508)
10-01-2006 5:59 PM
Reply to: Message 45 by melatonin
09-30-2006 9:03 PM


note ...
If you look at the post with the {Peek} button (it will open another window) you can see how the coding was done.

Note -- it is usually considered bad form to link directly to images on other sites ("deep links") as it can cause high bandwidth use on those sites. There are some options for uploading images (mirroring them), but reference to the original site should also be provided. Admin can help with image hosting.

(another wish-list item -- automatic conversion of all image links to be uploaded - like avatars - and linked to the original site)

Enjoy.


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Hawks
Member (Idle past 4698 days)
Posts: 41
Joined: 08-20-2006


Message 47 of 65 (353528)
10-01-2006 8:55 PM
Reply to: Message 32 by skepticfaith
09-29-2006 3:17 PM


Re: Mutations.
I did not suggest any drastic change but said we mustobserve a few beneficial mutations related to the brain during the time of civilization. Additionally, from the dawn of civilization there was more natural selection pressures from humans to have even bigger brains and thus there should be some small indication of change from that period.
So in effect, we just need to find a small increase in brain size from the dawn of civilization to present - that is all. Has this been obvserved or not?

There is no must for beneficial mutations to have occured during the time of civilization. And if there were any, they would not have to be increases in brain size.


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melatonin
Member (Idle past 4760 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 48 of 65 (353533)
10-01-2006 9:19 PM


There are maybe half a dozen genes that are attracting special attention by Lahn's research group. Here's an abstract of a recent paper from his group.

Science 9 September 2005:
Vol. 309. no. 5741, pp. 1720 - 1722
DOI: 10.1126/science.1116815
Prev | Table of Contents | Next

Reports
Ongoing Adaptive Evolution of ASPM, a Brain Size Determinant in Homo sapiens
Nitzan Mekel-Bobrov,1,2 Sandra L. Gilbert,1 Patrick D. Evans,1,2 Eric J. Vallender,1,2 Jeffrey R. Anderson,1 Richard R. Hudson,3 Sarah A. Tishkoff,4 Bruce T. Lahn1*
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.


http://www.sciencemag.org/cgi/content/short/309/5741/1720

This particular variant is not present in all humans but is the most recent development found. So, although it appeared around 6000 years ago, it doesn't really help a creationist viewpoint. Another more recent paper has questioned the notion the gene is undergoing positive selection (Currat et al., 2006). A mutation of ASPM causes microencephaly.

Employing the above strategy, we identified a number of candidate genes that might have played a role in human brain evolution. Examples include ASPM, Microcephalin, CDK5RAP2, CENPJ, Sonic Hedgehog, APAF1, and CASP3. A remarkable theme unifying all these genes is their involvement in determining neuronal cell number and brain size during embryonic development. When any one of these genes is mutated in either human or mouse, the result is a dramatically reduced brain size. For a subset of these genes, reduction in brain size appears to be the only discernible defect in the organism, indicating a highly specific function of the genes in regulating brain size. These findings led us to postulate that genes controlling brain size during development might have played a particularly important role in transforming brain size during evolution.

http://www.hhmi.org/research/investigators/lahn.html

These are the others that are under examination. Not to say these are the only genes involved in the evolution of the human brain, of course.

The Lahn group are doing some very interesting stuff.

Edited by melatonin, : iffy html code


  
Taz
Member (Idle past 1843 days)
Posts: 5069
From: Zerus
Joined: 07-18-2006


Message 49 of 65 (353629)
10-02-2006 1:01 PM
Reply to: Message 46 by RAZD
10-01-2006 5:59 PM


Re: note ...
RAZD writes:

it is usually considered bad form to link directly to images on other sites ("deep links") as it can cause high bandwidth use on those sites.


You know, you just gave me an idea

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RAZD
Member
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.1


Message 50 of 65 (362519)
11-07-2006 10:20 PM
Reply to: Message 47 by Hawks
10-01-2006 8:55 PM


Re: Mutations.
There is no must for beneficial mutations to have occured during the time of civilization. And if there were any, they would not have to be increases in brain size.

Also size is not necessarily 'beneficial':

  • a brain can be bigger and still not as well connected
  • a larger human brain can be detrimental when the mother and fetus die in childbirth
  • there are a lot of animals with larger brains than humans
  • size is NOT what is being selected
  • active mutations in connectivity are still occurring
  • the major difference between homo sap brains and the brains of other animals is in the degree of connectedness

The question on brain development in humans is WHAT is being selected.

Enjoy.


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42
Inactive Member


Message 51 of 65 (362546)
11-08-2006 2:29 AM
Reply to: Message 1 by skepticfaith
09-27-2006 4:39 PM


Chaos theory probably explains it - I' not an expert, but...

If you drop a plate and it breaks you get a few big bits and lots of medium sized bits and loads of tiny bits (and millions of teeny bits). Ice ages and other natural events exhibit this phenomenon, which I think is called "scale-free" phenomena. So, a concentration of mutations in a few generations is not astounding, and may be seen as special if one chooses to see it that way.


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RAZD
Member
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.1


Message 52 of 65 (362589)
11-08-2006 7:47 AM
Reply to: Message 51 by 42
11-08-2006 2:29 AM


So, a concentration of mutations in a few generations is not astounding, and may be seen as special if one chooses to see it that way.

If mutations are random then the distribution of beneficial ones within the full spectrum will also be random.

chaos theory probably explains it

It would be a good start.

If selection operates on mutations beneficial to a certain direction then any random mutations in that direction will be selected when they occur - and will also be randomly distributed over time.

The appearance of clumping is predicted by this mechanism.

Even without discussing whether or not mutations happen at a steady rate, or the rate oscillates around a medium that reacts to change in the environment.

Even without discussing WHAT the selection is for in human brain development.

Enjoy.

Edited by RAZD, : added second quote - hopefully got it right. when you edit you don't get the "message you are replying to" for reference anymore.


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melatonin
Member (Idle past 4760 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 53 of 65 (362723)
11-08-2006 8:25 PM


Thought this would be of interest in this thread...

Evidence that the adaptive allele of the brain size gene microcephalin introgressed into Homo sapiens from an archaic Homo lineage

At the center of the debate on the emergence of modern humans and their spread throughout the globe is the question of whether archaic Homo lineages contributed to the modern human gene pool, and more importantly, whether such contributions impacted the evolutionary adaptation of our species. A major obstacle to answering this question is that low levels of admixture with archaic lineages are not expected to leave extensive traces in the modern human gene pool because of genetic drift. Loci that have undergone strong positive selection, however, offer a unique opportunity to identify low-level admixture with archaic lineages, provided that the introgressed archaic allele has risen to high frequency under positive selection. The gene microcephalin (MCPH1) regulates brain size during development and has experienced positive selection in the lineage leading to Homo sapiens. Within modern humans, a group of closely related haplotypes at this locus, known as haplogroup D, rose from a single copy 37,000 years ago and swept to exceptionally high frequency (70% worldwide today) because of positive selection. Here, we examine the origin of haplogroup D. By using the interhaplogroup divergence test, we show that haplogroup D likely originated from a lineage separated from modern humans 1.1 million years ago and introgressed into humans by 37,000 years ago. This finding supports the possibility of admixture between modern humans and archaic Homo populations (Neanderthals being one possibility). Furthermore, it buttresses the important notion that, through such adminture, our species has benefited evolutionarily by gaining new advantageous alleles. The interhaplogroup divergence test developed here may be broadly applicable to the detection of introgression at other loci in the human genome or in genomes of other species.


Freely available to download here...
http://www.pnas.org/cgi/content/abstract/0606966103v1

So maybe these particular genes were introduced from neanderthals or another archaic homo group. Quite interesting and I guess it was a 'special event' for the two individuals involved ;)

Edited by melatonin, : added link


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RAZD
Member
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.1


Message 54 of 65 (362748)
11-08-2006 9:46 PM
Reply to: Message 53 by melatonin
11-08-2006 8:25 PM


... from neanderthals or another archaic homo group.

Perhaps Homo erectus or Homo ergaster?

http://www.dmanisi.org.ge/index.html

quote:
To day we have recovered more than twenty hominid remains in Dmanisi. This includes three mandibles, three hominid skulls and several postcranial parts.

The Dmanisi hominid remains are the first hominids discovered outside of Africa to show clear affinities to African H. ergaster rather than to more typical Asian H. erectus or to any European hominid.


They had basic stone tools, for whatever that is worth.

quote:
No bifaces or developed Oldowan artifacts have been found. Most of the artifacts retain sharp edges suggesting little transport and no refits of flakes or tools were observed. By the basic knapping technique Dmanisi lithic complex clearly belongs to the Oldowan or mode 1 industries. The Dmanisi artifacts are compatible with pre-Acheulean assemblages of East Africa .

Neander is not the only conclusion to reach here. Seems to be a romantic neo-european bias here ... :D

Enjoy.


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melatonin
Member (Idle past 4760 days)
Posts: 126
From: Cymru
Joined: 02-13-2006


Message 55 of 65 (362755)
11-08-2006 10:14 PM
Reply to: Message 54 by RAZD
11-08-2006 9:46 PM


romantic collective unconscious
There does seem to be some sort of implicit bias towards neanderthals, could be some sort of latent remnant/collective unconscious of the 'special relationship', haha.

Guess these guys can help consolidate the neanderthal interbreeding hypothesis...

Ancient DNA pioneer Svante Pääbo of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, says that this new work is "the most compelling case to date for a genetic contribution of Neandertals to modern humans." Indeed, Pääbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome.

http://sciencenow.sciencemag.org/cgi/content/full/2006/1106/1?rss=1

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RAZD
Member
Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.1


Message 56 of 65 (362856)
11-09-2006 10:28 AM
Reply to: Message 55 by melatonin
11-08-2006 10:14 PM


Re: romantic collective unconscious
Indeed, Pääbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome.

That would be the test. We had a thread on mtDNA evidence for neander mix, that pretty well showed no mitochondrial mixing, but that did not rule out the possibility of male neander genes.

Mammuthus was involved with the data IIRC.


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Joman
Inactive Member


Message 57 of 65 (362924)
11-09-2006 3:22 PM


I think that what's amazing about the brain isn't it's size but it's cognitive abilities. So, when I see a cartoon of a naked man that lived 1oo,ooo years ago looking unsure about, whether or not, the rock in his hand might be a tool, I know that he didn't have the cognitive brain I have.
It seems that brain size is supposed to be the great signature of the evolution of man. I suppose it's because it's the only remnant of the past that can be empirically measured which relates to the brain of man. This is a unfortunate state of affairs for the theory of evolution since, the data being discussed (brain size) is so crude that it can't ever rise to the level of scientifically rational extrapolation...er something other than hot air. The other data (quantity of mutations)only allows analysis of things as they are now.
What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools.
Without fire man can't cook, dry out nor keep warm. Man therefore, would've required adequate hair for survival. But, if man once upon a time had adequate hair there wouldn've been any need for clothes and so, any evolution of hair loss would've been immediately selected back out of existence.
Without tools man hasn't any advantage over nature. Without advantageous tools man would've perished in his competition with all the ferocious animals that do have all of the natural advantages.
Without clothing man can't protect his body against the perils of life in the wilds and will perish. It is interesting to note that the shame associated with nakedness has no evolutionary rationale.

I submit that the lack of these three things (fire,clothing,tools) can be proven to be life threatening.
So, without congitive ability man perishes. So, how did man survive until he obtained the benefit of cognitive thought? If man once had all the natural endowments of things needed for survival as a wild beast, there remains no rationale for natural selection of the loss of those very things.

BTW...what came first the eye's of man or the holes in his skull in which they fit, and funtion?

Joman.

Without tools man can't obtain advantage over his nature.


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Joman
Inactive Member


Message 58 of 65 (362925)
11-09-2006 3:23 PM


I think that what's amazing about the brain isn't it's size but it's cognitive abilities. So, when I see a cartoon of a naked man that lived 1oo,ooo years ago looking unsure about, whether or not, the rock in his hand might be a tool, I know that he didn't have the cognitive brain I have.
It seems that brain size is supposed to be the great signature of the evolution of man. I suppose it's because it's the only remnant of the past that can be empirically measured which relates to the brain of man. This is a unfortunate state of affairs for the theory of evolution since, the data being discussed (brain size) is so crude that it can't ever rise to the level of scientifically rational extrapolation...er something other than hot air. The other data (quantity of mutations)only allows analysis of things as they are now.
What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools.
Without fire man can't cook, dry out nor keep warm. Man therefore, would've required adequate hair for survival. But, if man once upon a time had adequate hair there wouldn've been any need for clothes and so, any evolution of hair loss would've been immediately selected back out of existence.
Without tools man hasn't any advantage over nature. Without advantageous tools man would've perished in his competition with all the ferocious animals that do have all of the natural advantages.
Without clothing man can't protect his body against the perils of life in the wilds and will perish. It is interesting to note that the shame associated with nakedness has no evolutionary rationale.

I submit that the lack of these three things (fire,clothing,tools) can be proven to be life threatening.
So, without congitive ability man perishes. So, how did man survive until he obtained the benefit of cognitive thought? If man once had all the natural endowments of things needed for survival as a wild beast, there remains no rationale for natural selection of the loss of those very things.

Admin message: The below is not on topic. The above is not necessarily entirely on or off topic - care must be taken when responding to it. Note to Joman - with some refinement it might suit a PNT

BTW...what came first the eye's of man or the holes in his skull in which they fit, and function?

Joman.

Edited by AdminModulous, : No reason given.


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nwr
Member
Posts: 5611
From: Geneva, Illinois
Joined: 08-08-2005
Member Rating: 4.7


Message 59 of 65 (362935)
11-09-2006 4:37 PM
Reply to: Message 57 by Joman
11-09-2006 3:22 PM


fire, clothing, and all that.
What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools.

The Tasmanian aborigines were rather primitive:

"The French savants of the Baudin Expedition, who observed the Tasmanians in 1802, were amazed that even though the Tasmanians lived in an often bitterly cold climate, they lacked clothing. Extraordinarily, they also lacked the ability to make fire. Mannalargenna, one of the last of the Tasmanian Aborigines to live a traditional life, told of what would happen if a group's fire was extinguished. He said that people had no alternative but to eat raw meat while they walked in search of another tribe. Significantly, one of the universal laws among the Tasmanians was that fire must be given whenever requested, even if the asker was a traditional enemy who would be fought after the gift had been given.
See http://www.ecobooks.com/books/futureat.htm
I'll note that this seems to be partly contradicted by http://www.monash.edu.au/news/releases/2003/jan03-fire.html
For another page on these peoples, see http://www.cwo.com/~lucumi/tasmania.html

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RAZD
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Posts: 20714
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 2.1


Message 60 of 65 (362971)
11-09-2006 8:42 PM
Reply to: Message 58 by Joman
11-09-2006 3:23 PM


oh. dear.
Welcome to the fray Joman,

I think that what's amazing about the brain isn't it's size but it's cognitive abilities.

Which is only a matter of quantity (not quality) compared to the cognitive ability of other apes or even other animals. A recent article talks about elephant self recognition as one of many examples of cognitive ability in other animals.

Cognitive ability is related to connectedness as well as to size - of the surface area rather than volume (hence the convolutions).

So, when I see a cartoon of a naked man that lived 1oo,ooo years ago looking unsure about, whether or not, the rock in his hand might be a tool, I know that he didn't have the cognitive brain I have.

So you base your understanding of ancient man on cartoons? Interesting.

It seems that brain size is supposed to be the great signature of the evolution of man. I suppose it's because it's the only remnant of the past that can be empirically measured which relates to the brain of man.

Homo neanderthalus had larger brains than Homo sapiens, but were not able to compete with us (even with tools), and there are many other species with larger brains, therefore SIZE is NOT the "signature" you are looking for. A more accurate claim would be cognitive ability, which as you (correctly) note, is not necessarily associated with size.

Even there, we see a gradation between all animals, with several species having individuals with cognitive ability that overlaps those of individual humans at the low end of the human spectrum.

As for what remains as evidence in fossil skulls, it is not just the size of the skull but the size and distribution of different parts of the brain within the skulls as we transitioned from ape ancestor to homo sap, and this can also tell us details about the development of the "special" human brain.

From Message 60:

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.
color yellow for empHASis.

So we don't just have brain SIZE for evidence, we also have relative areas and their development and change over time.

KNM-ER 1470 is the "type" fossil for Homo rudolfensis, that lived about 1.8 million years ago and is skull (F) in the picture shown later in this post.

This is a unfortunate state of affairs for the theory of evolution since, the data being discussed (brain size) is so crude that it can't ever rise to the level of scientifically rational extrapolation...er something other than hot air.

I love it when people confuse their misunderstanding of evolution with it being a problem for science.

Evolution is the change in species over time, so when we see evidence for change in species over time, how is that a "problem" for evolution?

And there is plenty of evidence FOR the change in species over time resulting in larger brain capacities in the lineage of human ancestry:


Click to enlarge

(Source of this picture is http://www.talkorigins.org/faqs/comdesc/hominids.html)

The other data (quantity of mutations)only allows analysis of things as they are now.

Except that we can compare the same data for closely related species - chimpanzees, bonobos, gorillas, etcetera, and see what elements were common and what are different.

What convinces me that the theory of evolution is falsified by these circumstances is my belief that man, can't survive, and couldn't have survived without cognitive ability enabling man to use fire, clothing and tools.

So you are convince by your incredulity without any reference to facts or evidence?

In addition to nwr's evidence in Message 59, we also have the record of Darwin in Tierra del Fuego

quote:
Here, two of Captain Cook's men died of the cold. WE went up to the same mountains the same day in the month AS THEY. Here you find the savage in plenty. Picture to yourself a canoe along side of a ship; with two or three men with as many women and a child, perhaps two, all absolutely naked.

And certainly in Africa - where hominids evolved into Homo sap - there is not an issue of needing clothes or fire to keep warm.

Apes also use tools and survive.

Without fire man can't cook, dry out nor keep warm. Man therefore, would've required adequate hair for survival.

Your argument is based on your personal incredulity that this could have occurred. All you prove by this argument is your incredulity and your inability to imagine.

We don't need to imagine clothes in Africa. We don't need to imagine fire to eat food without it, a practice still used in the world today (funny as it may seem).

But, if man once upon a time had adequate hair there wouldn've been any need for clothes and so, any evolution of hair loss would've been immediately selected back out of existence.

When it comes to hair, what you are forgetting (or are ignorant of) is the force of sexual selection, and how it can select for a feature that may have less survival fitness, but gets passed on because it boosts reproductive success.

Selection for a feature that threatens survival in those that best express it while at the same time showing evidence for increased selection in that direction is a signal of (Fisherian) runaway sexual selection. And selection continues to this day for humans to show less hair.

If you are interested in more information on this issue go to Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human Evolution, especially Message 44

It is interesting to note that the shame associated with nakedness has no evolutionary rationale.

And it is very interesting to note the total lack of shame in many native people that go naked day after day. All you are doing is projecting your personal (unnatural?) feeling onto others.

The ladies in the (copyright) picture here: "a picture brought back from south africa to australia by my great grandfather in the early 1900s featuring two native girls " are neither shamed nor cold nor huddled around a fire.

I submit that the lack of these three things (fire,clothing,tools) can be proven to be life threatening.

The facts above prove your hypothesis is false, but it is also false on several levels, not least of which is your assumption of all or nothing in these developments, while the evidence shows gradual developments in all those cultural features that benefited the ancestors that used them.

So, how did man survive until he obtained the benefit of cognitive thought?

By ignoring your argument from incredulity and your straw man argument. The way animals in the world today survive in spite of your ignorance of evolution.

BTW...what came first the eye's of man or the holes in his skull in which they fit, and function?

Please take this to a new topic (see Forum Proposed New Topics) so we can discuss how eyes existed before bony skulls, before mammals, before primates, before apes and before humans, without taking this thread off topic and getting a bunch of people suspended for answering such a ... question here.

Enjoy.


type [qs]quote boxes are easy[/qs] and it becomes:
quote boxes are easy


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to share.


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 Message 58 by Joman, posted 11-09-2006 3:23 PM Joman has not yet responded

  
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