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Author | Topic: Human Brain Evolution Was a 'Special Event' | |||||||||||||||||||
RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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Hawks Member (Idle past 6177 days) Posts: 41 Joined: |
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 6239 days) Posts: 126 From: Cymru Joined: |
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:
Just a moment...Vol. 309. no. 5741, pp. 1720 - 1722 DOI: 10.1126/science.1116815 Prev | Table of Contents | Next ReportsOngoing 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. 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.
Bruce T. Lahn, PhD | HHMI 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
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Taz Member (Idle past 3322 days) Posts: 5069 From: Zerus Joined: |
RAZD writes:
You know, you just gave me an idea 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.
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RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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':
The question on brain development in humans is WHAT is being selected. Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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42 Inactive Member |
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 (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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melatonin Member (Idle past 6239 days) Posts: 126 From: Cymru Joined: |
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
Freely available to download here... 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.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 (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
... from neanderthals or another archaic homo group. Perhaps Homo erectus or Homo ergaster? http://www.dmanisi.org.ge/index.html
quote: They had basic stone tools, for whatever that is worth.
quote: Neander is not the only conclusion to reach here. Seems to be a romantic neo-european bias here ... Enjoy. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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melatonin Member (Idle past 6239 days) Posts: 126 From: Cymru Joined: |
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 Pbo 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, Pbo says, he will now search for the haplogroup D variant of microcephalin in his own studies of the Neandertal genome.
http://sciencenow.sciencemag.org/...content/full/2006/1106/1
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RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Indeed, Pbo 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. we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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Joman Inactive Member |
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 |
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 PNTBTW...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: 6412 From: Geneva, Illinois Joined: Member Rating: 5.3 |
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 The Future Eaters by Tim FlanneryI'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 Succeed.Net Broadband Internet and VOIP services - SUCCEED.NET
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RAZD Member (Idle past 1435 days) Posts: 20714 From: the other end of the sidewalk Joined: |
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. color yellow for empHASis. http://www.massey.ac.nz/~alock/hbook/brain.htm
quote:Note that specimen KNM-ER 1470 is in the above referenced chart as skull (F). continuing:
quote: 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:(Source of this picture is 29 Evidences for Macroevolution: Part 1) 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: 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 Proposed New Topics) so we can discuss how Enjoy. quote boxes are easy we are limited in our ability to understand by our ability to understand RebelAAmericanOZen[Deist
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