Genetics and Human Brain Evolution

The actual number is unimportant. The important thing is the relation of similarity between human and chimpanzee as compared to the similarity between human and gorilla or between chimpanzee and gorilla or between human and neanderthal and between chimpanzee and neanderthal - that show how closely related the different species are genetically.What the number actually is becomes irrelevant compared to always ending up with humans closer to chimpanzees than gorillas, chimpanzees closer to humans than gorillas and neanderthals in between chimpanzees and humans in relatedness (but not linearly between).Some of this has been discussed before on Comparisons of Neandertal mtDNA with modern humans and modern chimpanzees (although some of the graphics don't seem to load).There have also been a number of threads on similarity:
We're Really Chimps???
"Homo troglodytes" Genome Project, DNA 96% {us}
From chimp to man: it's as easy as 1, 2, 3!
Chimpanzee-human genetic gapAnd it seems all the studies still put us in the Chimpanzee neighborhood regardless of the actual number of genetic sequences that are identical. I don't find this surprising at all, we've seen from the fossil evidence that brain size grew rapidly compared to other evolutionary changes in the species preceding Homo sapiens. Other than this being a standard argument from incredulity, there is no reason why substitutions in the areas related to significantly evolved features should not show a high degree of substitutions and other changes, especially compared to areas related to rather less significant changes.I also suspect that there are a number of other brain related genes that show significant variation between chimpanzees and chickens, and that an unbiased debater would mention them as well.But the real question you are asking in this oblique way, is how can some species have accelerated rates of evolution of some features while other related species do not eh?The answer is selection pressure.All species have roughly the same rates of mutations in similar areas, and these rates would be more similar the more related the species are yes?Species living in the same environment would also have essentially the same survival selection pressure, and this pressure would also be more similar the more related the species are yes?This would argue that the genetic relationship between humans and chimpanzees should be closer than chickens on pretty much every gene sequence, right? Except for one thing: sexual selection.Sexual selection operates at every generation, not waiting for some disaster to change the environment to cause selection pressure on the individuals in a population. Normally this selection pressure operates to keep populations centered around a mean value - the most average individuals get the most breeding opportunities.Runaway Sexual Selection though operates to one side of average and can drive a species to a heavy bias in one direction of evolution. Fisher described this process. Peacock tails are a normal example of this, but one of many in the bird family. Closely related species can be totally drab and inconsequential compared to the flamboyant species marked by Runaway Sexual SelectionThis can be discussed separately (so as not to drag this topic off on a tangent) on Sexual Selection, Stasis, Runaway Selection, Dimorphism, & Human EvolutionThus sexual selection can provide for very intense selection pressure on a species that far outranks normal selection pressure, and this higher selection pressure will result in a higher number of mutations being selected that offer the desired (literally) result.Is this enough to conclude that sexual selection operated on the evolution of the human brain? No, but it is indicative, and the fact that we have other features that show similar effects of runaway sexual selection also lends credence to the concept:

• extremely long head hair, much longer than any other primate on any part of its body,
• extremely large male penis compared to any other ape species,
• extremely large and constantly 'full' breasts compared to any other ape species,
• extremely bare appearing skin, especially in females, compared to any other ape species, to the point where it requires behavioral adaptations for survival,
• the aspect of 'neoteny' that is more fully developed in humans than any other ape species,
• and finally, large brain size, bigger than any other ape species ...

Some of these may be inter-related (neoteny and 'bare'ness), but others aren't. Ones that can hinder survival in fully developed features are also indicative of "peacock" like runaway sexual selection, and the large head of humans fits this scenario as well -- any larger and it threatens the life of both the mother and the child.We have multiple features showing evidence of extreme sexual selection, and ONE of them relates directly to the brain development in humans. There is also evidence that this sexual selection is still on-going: body shaving is becoming more common and extensive, for instance, and we need hardly mention porn to conjure up images of certain body types, sexual features, and sexual preferences.The conclusion is that we are "human" because of sex.The genetic data just confirms this eh?Enjoy.

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RebelAAmericanOZen[Deist
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If you read the other links you will see that I have. I will see how you respond to Mick on your cherry=picking of statistics - this is twice now this issue has been brought up.Meanwhile I can't help but notice you did not say anything with regard to the real issue - the fact that no matter WHAT the number is we are still more closely related to chimpanzees genetically than to any other known living species, and that there is a definite progression from human to neander to chimp to gorilla etc.I also noticed that you didn't address the issue of sexual selection that can easily cause the kind of rapid evolution you are complaining is not possible.Please stop dancing around and address these issues when you return, rather than continue to misquote or misrepresent materials and sources.Enjoy.Edited by RAZD, : tpoy

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RebelAAmericanOZen[Deist
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Not really, because human did not "leap" from chimpanzees. A better picture of what this thread is about is:
(Source of picture is 29 Evidences for Macroevolution: Part 1)Of course actually showing the intermediate stages - transitionals - kind of takes the impression of a "giant leap" out of the picture doesn't it?Enjoy.Edited by RAZD, : added picture source information

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RebelAAmericanOZen[Deist
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No, it's more than a cliche that scientists use evidence to back up their theories. Creationists however love to ignore evidence and pretend they can keep repeating the same position no matter how much evidence is given that refutes it.I noticed you still did not address the issue:
(Source of picture is 29 Evidences for Macroevolution: Part 1)Showing the intermediate stages - transitionals - still takes the impression of a "giant leap" out of the picture doesn't it?Here is the key to the picture:

quote:

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(A) Pan troglodytes, chimpanzee, modern
(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
(I) Homo heidelbergensis, "Rhodesia man," 300,000 - 125,000 y
(J) Homo sapiens neanderthalensis, La Ferrassie 1, 70,000 y
(K) Homo sapiens neanderthalensis, La Chappelle-aux-Saints, 60,000 y
(L) Homo sapiens neanderthalensis, Le Moustier, 45,000 y
(M) Homo sapiens sapiens, Cro-Magnon I, 30,000 y
(N) Homo sapiens sapiens, modern

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The skull image you used (H)... ... is in the middle of the transitions from Australopithecus africanus to modern human.The fact that there is a clear trend from (B) to (N) in the picture is what evolution predicted - and further predicts that more intermediates will be found to fill in even those "gaps".You haven't addressed the issue of sexual selection that allows faster adaptations for run-away features than for normal features, and the only argument you have is your personal incredulity that what we see in genetics and in fossil evidence could not have happened naturally.Unfortunately for you, nature is not constrainted in any way by your incredulity.Enjoy.

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RebelAAmericanOZen[Deist
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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. 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. Care to substantiate that with the scientific paper that cites that exact thing? Or do we deal with another creationist misrepresentation site. 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. Do you ever read the posts? Or do you not know what the catalogue ID's are\look like? 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? The scientific one: that it shows evidence of features intermediate in form and development between the ancestor and the progeny. 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. 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. 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

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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.

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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.

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Note that specimen KNM-ER 1470 is in the above referenced chart as skull (F).continuing:

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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.

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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):

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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.

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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)

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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.

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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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RebelAAmericanOZen[Deist
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small correction Don't confuse a species human LCA with the LCA for separation of our species from a previous species. (LCA is such a misconception :rolleyes. The LCA within a species will always be able to be substantially younger than the LCA for that species and their closest cousin species.If we are talking about the genetic pool that included the oldest known Homo sapiens, when our species may have branched from other Homo species, then make that 160,000 to 200,000 years ago (minimum). In Ethiopia:
http://www.berkeley.edu/.../releases/2003/06/11_idaltu.shtml
Ethiopia is top choice for cradle of Homo sapiens | Nature
(You'll have to sign in to access the second).That doesn't change the fact that this is long after both Homo neanderthalis and Homo erectus had emigrated into europe and asia.Nor does this have any bearing with how much more ancient the last common ancestor with chimpanzees lived. In africa.Having a LCA younger than the emigration from africa WOULD be a problem.Enjoy.

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RebelAAmericanOZen[Deist
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I guess this means there will be no answer to the question of sexual selection (Message 11, Message 16, Message 33, and Message 60) providing a mechanism for accelerated selection of certain "desired" features, the correlation of sexual selection types of evidence with humans, demonstrating sexual selection has been and continues to be a shaping force on human evolution ... including selection for more creative brains ...and further that we won' t have that promised (Message 42) "walk through the shelf of skulls" that show the transition in skull sizes with no sudden jump (Message 33), to see you attempt to "debunk this optical illusion with substantive details" ... when it would be so easy to provide those "details" should they really exist."So much for the gay art of cloud riding ..."... denial (or running away when you can't refute it) does not make evidence go away.Enjoy.

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RebelAAmericanOZen[Deist
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I'm not a geneticist and I understand where you went wrong here. Each and every gene has different lengths, they even vary from person to person for similar genes as well.So talking about mutations per gene or mutations per strand of DNA is not being very precise.In order to be more precise you need to normalize the data, make it dimensionless or set it to some arbitrary standard, and they do this by dividing by base-pairs as a unit of length.Within that unit length they then measure mutations per generation, and these rates can be used in a more univerally applicable way: it's more precise.What it does NOT say is that every base pair mutates that amount every generation. Why not? indels, reversals, all the other ways and means that big chunks of DNA get swapped around are included in those figures.What the measurement really means as I see it, is {mutations per generation} in a standard arbitrary unit length of DNA. I'll be happy to have one of the professionals correct me if this is wrong, but that is what I get from reading it. ... and once again I note that the actual number, to whatever decimal point you care to take the argument, is irrelevant compared to the relative relationships between species.Chimpanzees are the closest living relative we have no matter what the actual number is, because all the others have less in common, and any changes to the numbers for chimps-humans will also affect the numbers for othes-human.Chimps are also closer related to humans that various species in other genera\families, and this is because they really are hominids.You dismiss the genetic information with some mumbo-jumbo personal interpretation of the data, which you then organize to show that you can't believe that it could happen. This is called a straw man argument followed by an argument from incredulity - both logical fallacies.But you also fail to address the parallel information from fossil evidence showing gradual changes accumulating over time in the size of the human brain, as well as evidence for accelerated sexual selection: your only answer was your claim that your interpretation of the genetic data makes the fossil evidence wrong.It doesn't work that way. Your interpretation fails to explain the fossil evidence, therefore IT is wrong. ... unless you are wrong and you just don't realize it.Dawkin's famously lists four causes for this kind of attitude: stupidity, ignorance, malice and delusion. ... that this has nothing to do with gentics or human brain evolution?Or is it really indicative of your failure to {see\know\understand} what other people are saying? That you start with the conclusion that you are right, and that anyone who disagrees with you is wrong, that whatever they post that doesn't fit your personal interpretation is an error. ... your personal perversion of science.That's the wonderful thing about the internet: anyone can post whatever opinion they have as if it were fact. The ultimate anarchy of expression.It still does not make you right, nor does it address the errors in your thinking. Denial never does. Ignorance of the evidence never does. ... you're just venting your personal emotional response to being unable to deal with the facts.But how was intimidation ever the intention eh? Or is that what you thought you were doing here? Certainly that attitude matches your abusive, arrogant and unyielding behavior. ... but it is miniscule compared to a lifetime of learning.And the length of time spent is irrelevant when there is incomplete comprehension. A world-wide conspiracy aligned against you? Or delusion”Poor fella.Enjoy.Edited by RAZD, : added info

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RebelAAmericanOZen[Deist
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regarding Message 97 and Message 113Edited by RAZD, : unnecessary commentsEdited by RAZD, : changed my mind, intentionally ...

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RebelAAmericanOZen[Deist
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{X} mut/bp/gen = {X} mut x 1/bp x 1/gen = {X} mut/(bp*gen)32.2 ft/sec/sec = 32.2 ft/sec^{^2}To think that 32.2 ft/sec/sec = 32.2 feet would be an error of some incalculable gravity.Enjoy.Edited by RAZD, : for fun

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RebelAAmericanOZen[Deist
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My response to you is at Message 91 where this issue is more on topic than on this thread.Enjoy.

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RebelAAmericanOZen[Deist
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From australopithicus to homo sap = ~3 million years, at an average of ~25 years per generation is ~3,000,000/~25 = ~120,000 generations.Using your number of 145 million base pairs for the genetic sequence in question (for the sake of argument) and applying the formula:0.00000002 mutations/bp/gen x 145 million bp x 120,000 gen = 348,000 mutations. Accumulated in that section of the human genome since Lucy walked the earth.And that is all it says.Notice that the units cancel:{X}(bp) x {Y}(gen) x {Z}(mutations)/(bp)/(gen)
= {X}{Y}{Z} (bp)(gen)(mutations)/(bpxgen)
= {X}{Y}{Z} (bpxgen)(mutations)/(bpxgen)
= {X}{Y}{Z} mutations. And "bp" and "gen" are not variables that you plug {values} into to get results. They don't have {values} that CHANGE the rate of mutation, they are PART of the rate of mutation. The RATE is already given. It is just an average rate of the number of mutations per (base pair) per (generation).-----And you still haven't answered the question about the fossil skulls that show a gradual progression in size from australopithicus to homo sap, thus validating that there has been a rather constant change in the volume of the brain,NOR have you dealt with the issue of sexual selection that can cause an accellerated degree of selection towards a "desired" feature,NOR how the size of the brain being at the maximum end of the range for survival of mother and fetus shows it is likely a result of runaway sexual selection.With this information the number of mutations given is not a surprise, nor a quandry.Enjoy.

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RebelAAmericanOZen[Deist
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