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Author
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Topic: Support for PEH
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DaveScot
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Member # 1545
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posted 14. May 2006 20:38
BFast
quote:
We seem to have seen a phenominon where different chromosome counts are very effective at separating species. If the chromosome count is different, then, in all of the species so far discussed, fertile offspring is, at best, rare.
The house mouse can have anywhere from 2n = 22 to 2n = 40 chromosomes and all are the same species.
One should also consider that chromosome counts typically number less than 100 and there are some 10 million different species on the planet. That means that vast numbers of different species share the same chromosome number.
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Scott
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posted 14. May 2006 21:11
Humans are more closely related to rabbits than are Guinea Pigs. =P
I've always wondered about chromosome counts and evolutionary relationships. Is anyone aware of a phylogenetic tree that shows chromosome counts and what it would have taken to get to current counts from the presumed common ancestors?
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Christopher D. Beling
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Member # 723
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posted 15. May 2006 01:48
Bruce, I don't know if you are aware of the work of Donald Forsdyke on speciation (click here) - Donald like John in his PEH sees chromosomal rearrangements as being essentially the mechanism behind speciation: He quotes:
quote:
My own work (i.e. Donald Forsdyke's), which is opposed by the genic school, has suggested that the intrinsic “peculiarity” of Romanes, the “complementary factors” of Bateson and the “patterns” of Goldschmidt are none other than Erwin Chargaff’s species-dependent component of the base composition. Differences in the (G+C)% pattern would impede the pairing of chromosomes at meiosis, resulting in hybrid sterility. This internal non-genic barrier may be the most usual form of reproductive isolation permitting phenotypic differentiation within a species without geographic isolation, and with or without the influence of natural selection. Species arrival may or may not be immediately followed by genic differentiation for species survival, although natural selection will play a role in later phenotypic differentiation
Well, this gives some of Donald's ideas behind what causes the species barriers to form quickly.
With regard to speciation I think we need to take seriously the idea of the SMH seriously and the C+G% trigger mechanism of Donald Forsdyke's group. We may very well be dealing in speciation with what we in physics call a "phase transition" (or cooperative phenomenon) - perhaps that something occurs in the environment of the species that causes an instability - (i.e. on the C+G% hypothesis the concentration of C+G in the genome gets too high to restrain the old chromosome arrangement - and something snaps). [The analog in physics would be the slight lowering of temperature from +1C to -1C and a whole mass of water suddenly switching from the liquid phase to the solid phase]. Perhaps there is a sudden transition across the whole species when new environmental conditions prevail - which explains why the offspring can find others of similar karyotypes to mate with - and a new species type is formed within just a generation or two? I haven't seen the work of Donald Forsdyke discussed yet - it seems highly relevent. Chris
[ 15. May 2006, 02:24: Message edited by: Christopher D. Beling ]
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John A. Davison
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Member # 1425
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posted 15. May 2006 07:54
Chris
I note that you use the present tense in such terms as "species arrival." I ask what species arrival? I have repeatedly requested examples of recent speciation stemming from known sources and received no responses. I have also asked for examples of any two known species, fossil or recent where it can be established that one is ancestral to the other with the same result - no response. Until such examples are forthcoming the only reasonable conclusion is that, like ontogeny IS now, phylogeny also WAS a self-terminating phenomenon.
This in no way pleads against a past evolution. What it does indicate is that obligatory sexual reproduction is incapable of creative evolution and can only produce varieties.
It is considerations like these that literally forced me to consider the semi-meiotic hypothesis (SMH) as a reasonable alternative to Darwinian gradualism. It should be remembered that the first meiotic division is a perfectly valid means of diploid reproduction in its own right since it takes the chromosome complememnt from tetraploid to diploid in a single cytogenetic event, the first meiotic division. Just as important, it automatically can produce new homozygous chromosomal karyotypes in a single step, theoretically a new species, while at the same time it preserves the original species configuration these in equal frequencies. Also in ordinary mitosis the chromosmes complement does exactly the same thing. It goes from diploid to tetraploid and then back to diploid. The difference is that mitosis is entirely conservative while the first meitic division is potentially enormously creative.
The SMH also recieves support from another aspect of meiosis. Meiosis involves two discrete events, the first and then the second meiotic division. Surely the second cannot take place before the first. I regard this as evidence that the first division is the more primitive and accordingly must have evolved before the second.
With the second division, the chromosome complement became haploid and the only way it has been restored to the diploid condition is through mandatory sexual reproducution. This is one of the primary reasons that I regard sexual reproduction as fundamentally anti-evolutionary just as I regard Mendelian (sexual) genetics as such. Like it or not, not a single novel new life form has ever been produced through the known devices of sexual reproduction. All the allelic substitutions in the world will not produce new species or any of the higher taxonomic categories. I now regard that as quite impossible.
Grasse expressed a similar view:
"Aren't our plants, our animals lacking some mechanisms which were present in the early flora and fauna?
Evolution of Living Organisms, page 71
I recommend that entire paragraph, of which I have quoted only the last sentence, be seriously considered by any objective student of evolution. Grasse is one of my most valued sources, probably the greatest French biologist of his generation just as his counterpart, the Russian biologist, Leo Berg, was of his.
The SMH provides that mechanism and I am confident that everything we now know remains in accord with its implications. I know of absolutely nothing that precludes its validity. Until such time as it is proven to be in error I will adhere to it, especially since the Darwinian paradigm is a total disaster. Evolution did occur, of that I am certain, and there is no compelling evidence that it still is.
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Bruce Fast
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Member # 924
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posted 15. May 2006 12:15
Christopher D. Beling, Thanks for the link to Donald Forsdyke. However, the fact that mice, as a single species, have between 22 and 40 chromosomes causes me to seriously question the validity of a chromosome case for or agains the speciation question. Certainly the argument that species separation can be determined simply by chromosome counting doesn't hold water. It is clearly possible to have creatures with very different chromosome counts happily mating and producing fertile offspring. At least that's what my mouse-trap is telling me.
However, the fact that the choromosome count issue is so totally destroyed by mice has also caused me to wonder whether there is any "intermediate form" interpretation to be found here either. If the chromosomes could only change by 2 or maybe 4 before speication set in, then an organism that contains a count differing by 2, but happily mating could be seen as an intermediate form. However, mice, with a near 50% variation in chromosome count, simply causes the chromosome counting argument to be thrown out the window as far as I am concerned, even though it seems to have varacity with other species.
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John A. Davison
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Member # 1425
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posted 15. May 2006 16:09
I recommend that those reports of mouse intraspecific chromosome count variation be treated with some skepticism. What is the source of that information - Wikipedia? Where is reference to the original literature? Frankly I don't believe it and certainly will not accept it without verificiation. Chromosome number variation is common within genera but rare within species, especially in animals.
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John A. Davison
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posted 15. May 2006 16:16
I checked the source and what seems to be missing is the evidence for hybridization between the presumed "races." In other words are these really all the same species? What is the fate of their hybrids? I just don't know. Has that been investigated? If it hasn't it sure should be.
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DaveScot
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posted 15. May 2006 16:28
BFast
The truth of the matter is that we understand next to nothing of what's going on at the molecular level in living cells and that's where all the action is. We don't know what all is going on with bacteria with genomes of a hundred thousand bases and we certainly don't know what's going on in the vastly more complex genome of a human being. But we're making progress. We have all the raw code and pretty much all the tools needed to get to the bottom of it all. It's just a matter of time. It's probably a good idea at this point to wait for the definitive results before jumping to conclusions. It could be a long wait but perhaps not for the simplest bacteria and since they employ the same basic protein factory as all other living things once we have that figured out the rest should be much easier. A badly needed milestone right now is being able to predict protein folding. We need a quantum leap in computer technology for that. And when I say quantum I do mean quantum as in quantum computing.
In the meantime it would be nice to be able to test Davison's hypothesis but I can't seem to get a straight answer from him on how to acquire the animals needed to conduct the experimental verification. If he doesn't know or won't say I wonder if anyone can. Maybe no one has tested it because it's not possible or practical. Sort of like testing the Darwinian claim that the flagellum self-assembled without any outside help.
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John A. Davison
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Member # 1425
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posted 15. May 2006 17:15
While it is true that chromosome counts mean very little, the total DNA per cell can be a very important consideration in determining relationships. For expmple in the genus Hedera, English Ivy, there are many "species" with varying numbers of chromosomes but the total DNA is remarkably the same in all. Those with many chromosomes have smaller chromosomes than those with a few. Theoretically those with large but few chromosomes should have slightly less DNA per cell because they have fewer telomeres and centromeres. The extent to which forms with different chromosome numbetrs can be considered to be the same species depends on one thing only. If the chromosmes can pair (synapse)successfully and separate without breakage during meiosis they will be able to produce balanced gametes and should be considered races, not species. That may be the case with the house mouse as well. Nevertheless a thorough analysis of the reproductive fate of hybrids is always important in establishing species identity. Unfortunately that is not always done. Darwinians hate to do experiments and have been ever since Dobzhansky shot down selection with Drosophila, the favorite evolving guinea pig of Darwinian mysticism. Now they just assume that any genetic change is creative evolution on a grand scale. It is ridiculous to say the least.
Don't take my word for it.
"The fruitfly (Drosophila melanogaster), the favorite pet insect of the geneticists, whose geographical, biotropical, urban and rural genotypes are now known inside out, seems not to have changed since the remotest times."
Pierre Grasse, Evolution of Living Organisms, page 130.
Evolution is finished folks. It simply is no longer in progress. Get used to it. Homo sapiens was the last significant product and most certainly the last mammalian species to be produced. In my opinion from here on it is all down hill.
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Bruce Fast
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posted 15. May 2006 18:58
DaveScot: "The truth of the matter is that we understand next to nothing of what's going on at the molecular level in living cells and that's where all the action is."
That is approximately my understanding as well. I suspect that as DNA becomes well understood, the issue of whether individual mutational events, each challenged by selection, can account for it all will be established one way or the other. I personally expect that a "we can't get there from here" reality will perculate to the surface. At that point, ID will become mainstream science whether the scientific community likes it or not.
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John A. Davison
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Member # 1425
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posted 15. May 2006 20:50
David Springer
Has it ever occurred to you that if I knew how to obtain female frogs known to be heterozygous for chromosoem reorganizations, that I might have sought to obtain them? Apparently not. Need I say more? Why don't you find them for me and send me a few? Please note where they came from as I may need more of the same. Is that a straight enough answer for you or is this just one more of your chronically pathetic attempts to discredit me?
I also don't appreciate your Spanish Inquisition style of interrogation, especially as it comes from someone with no credentials whatsoever. Furthermore I have explained this matter many times before as you are well aware. You grow tiresome ss you continue to reveal your real motives which are to discredit one who has rejected both Darwinian atheism and the tenets of the Creationist camp to which you are now attached.
Try the same at Uncommon Descent where you serve as blogczar. You wouldn't dare and you know it.
Dembski would not permit it.
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Christopher D. Beling
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Member # 723
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posted 15. May 2006 21:09
Bruce,
quote:
However, the fact that mice, as a single species, have between 22 and 40 chromosomes causes me to seriously question the validity of a chromosome case for or agains the speciation question.
I understand your concern. I think it would be good to get that reference out for people to read. However, I would say that my limited reading in genetics tells me that there is such a thing a "polyploidy" were the karyotype can vary from 2N to 3N to 4N, and sometimes quite successfully without diminishing the fitness of the organism. You can read about this in the book by Futuyma Evolutionary Biology . In congruence with the SMH this "polypoidy" change in karyotype seems to occur at the 1st meiotic stage and the amount of genetic information remains the same - just copied thats all. I think the kind of change that causes speciation is things like joining together of chromosomes i.e. A+B=C, or the inversion of one piece of a chromosome - these are also described in Futuyma's book, and incidentally the case of inversion in John's 1984 paper. Look forward to hearing from you on this! Chris
[ 15. May 2006, 21:12: Message edited by: Christopher D. Beling ]
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John A. Davison
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Member # 1425
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posted 16. May 2006 02:32
Polyploidy is common in plants but quite rare in animals. In both it is an evolutionary dead end, just as is everything else apparently.
"A past evolution is undeniable. A present evolution is undemonstrable."
John A. Davison
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peter borger
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Member # 722
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posted 16. May 2006 04:59
Carefully reading the abstract shows that:
quote:
Phylogenetic analysis of the mtDNA sequences resulted in a parsimony tree which contained six major clades. Each of these clades contained both Rb and standard karyotype mice, consistent with the hypothesis that Rb races have arisen independently multiple times.
Apparently the same Rb strains evolved several times and must be regarded as the result of a NON-RANDOM reshuffling of the genome.
peebee
GUToB makes biology easy.
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DaveScot
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posted 16. May 2006 16:29
It's not polyploidy in mus domesticus. The normal chromosome number is 2n = 40 and the chromosomal variants are all 2n = 22 to 2n = 38.
I'm not sure why Peter thinks it's non-random reorganizations. There are a limited number of chromosome count results possible from Robertsonian fusion and it could be that hitting the same number on separate occasions is just the way the cookie crumbled.
As to why there are so many chromosomal races of house mouse I wouldn't be surprised if it's the result of the poor damn things being the target of so many poisonings by humans. Toxic chemicals in non-toxic quantity can really cause the old mutation rate to skyrocket.
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