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Evolution And Single Common Ancestory


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Poll: Is the single common ancestor model essential to the theory of evolution (9 member(s) have cast votes)

Is the single common ancestor model essential to the theory of evolution

  1. 1 Yes, that is the whole point of TOE (explain) (3 votes [33.33%])

    Percentage of vote: 33.33%

  2. 2 No, it could be discarded and replaces with...(explain). (4 votes [44.44%])

    Percentage of vote: 44.44%

  3. 3 Neither, (explain) (2 votes [22.22%])

    Percentage of vote: 22.22%

Vote

#1 Phaedrus

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Posted 20 June 2005 - 06:04 AM

Evolution is defined in biology textbooks and elsewhere as 'the change of alleles in populations over time'. Whatever you believe about natural history you would have to realize that allele frequencies change over time. However, the presumption that every living thing must have descended from a single common ancestor cannot be demonstrated or directly observed. Given the above definition structuralism, intelligent design and creationism are all a part of the theory of evolution, the only differences being ultimate origins and lines of descent.

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Posted 20 June 2005 - 06:32 AM

No. Common ancestry is an important aspect of the theory, but so long as every organism is theoretically traceable to a single common ancestor, it doesn't have to be a single single common ancestor. Since we still don't know much about abiogenesis, it's hard to estimate the liklihood of such an event occurring more than once, though intuitively, it seems quite unlikely.

Did you really intend that the discussion be directed to that, or did you want to talk about this?:

Given the above definition structuralism, intelligent design and creationism are all a part of the theory of evolution, the only differences being ultimate origins and lines of descent.



#3 Geezer

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Posted 20 June 2005 - 06:42 AM

What do you mean by single, common ancestor? Are you talking apes and humans - or the 1st cells - or what?

'the change of alleles in populations over time'


That is fairly simplistic. What barrier keeps populations from continuing to change? We see new species develop every day .

As for a single common ancestor - possibly from a cellular perspective - who knows? It can never be verified, regardless of scientific speculation.
I would need more info to answer fully.

An interesting Jewish perspective:
http://www.orot.com/ec.html

#4 Phaedrus

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Posted 20 June 2005 - 06:54 AM

No.  Common ancestry is an important aspect of the theory, but so long as every organism is theoretically traceable to a single common ancestor, it doesn't have to be a single single common ancestor.  Since we still don't know much about abiogenesis, it's hard to estimate the liklihood of such an event occurring more than once, though intuitively, it seems quite unlikely.

Did you really intend that the discussion be directed to that, or did you want to talk about this?:

View Post


When I say single I don't mean an individule, it could be a large population of single celled protoorganisms or an original F1 type of the originally created 'kinds' spoken of in Genesis. Stucturalism is also a concept that simply states that the Eukayote cells, for instance, need not develop its distictive features peicemeal. The question I am most interested in addressing is are there alternatives to this model of evolutionary lines of descent:

Darwin's tree of life

Had I thought of it I would have put this diagram in the OP. Instead of a single celled protoorganism I think special creation would be consistant with the scientific definition of evolution.

That is fairly simplistic. What barrier keeps populations from continuing to change? We see new species develop every day .


“Gärtner, by the results of these transformation experiments, was led to oppose the opinion of those naturalists who dispute the stability of plant species and believe in a continuous evolution of vegetation. He perceives in the complete transformation of one species into another an indubitable proof that species are fixed with limits beyond which they cannot change.”

Darwin proposed natural selection was the mechanism for the change of one species to another, the selection of most favored races, he called it. It was based on the 'geometric growth of populations', which claims that populations tend to populate beyond the ability of the resources to sustain them and there is a struggle to survive. The ones best 'fitted' would survive while the rest would die off, it is simplicity itself, natural selection is the elimination of the less fit. This is how Darwin and neodarwinians see nature, as a red in tooth and claw struggle for survival within a population yielding improved fitness. The only model Darwin offered in Origin of Species was what he called the tree of life starting with an undefined protoorganism and growing like a tree from that single stem into countless branches of living systems. The mechanism he proposed was natural selection:

"But if variations useful to any organic being do occur, assuredly individuals thus characterized will have the best chance of being preserved in the struggle for life; and from the strong principle of inheritance they will tend to produce offspring similarly characterized. This principle of preservation, I have called, for the sake of brevity, Natural Selection. Natural selection, on the principle of qualities being inherited at corresponding ages, can modify the egg, seed, or young, as easily as the adult."

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Posted 20 June 2005 - 08:11 AM

The question I am most interested in addressing is are there alternatives to this model of evolutionary lines of descent:

Darwin's tree of life

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I think the best way to answer that is to note that the tree of life proposed by Darwin represents an optimistically simplified model; more recent work suggests that things are not nearly so neat and tidy. I think most biologists now agree that a better metaphor for the evolutionary history of earth’s life forms is a fuzzy bush rather than a tall bifurcating tree.


When I say single I don't mean an individule, it could be a large population of single celled protoorganisms or an original F1 type of the originally created 'kinds' spoken of in Genesis.

My reading of Genesis does not obtain any hint of reference to single celled protoorganisms, and the possibility for horizontal gene transfer would seem to weaken the possibility of metaphorically extending the concept of 'kinds' quite that far.

#6 Phaedrus

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Posted 20 June 2005 - 01:25 PM

[quote name='Calipithecus' date='Jun 20 2005, 08:11 AM']
I think the best way to answer that is to note that the tree of life proposed by Darwin represents an optimistically simplified model; more recent work suggests that things are not nearly so neat and tidy. I think most biologists now agree that a better metaphor for the evolutionary history of earth’s life forms is a fuzzy bush rather than a tall bifurcating tree.[/quote]


My reading of Genesis does not obtain any hint of reference to single celled protoorganisms, and the possibility for horizontal gene transfer would seem to weaken the possibility of metaphorically extending the concept of 'kinds' quite that far.

View Post

[/quote]

What I'm getting at is multiple lines of descent and independant lineal starting points. In short, bacteria are bacteria and do not become eukaryotes. Suppose for a minute that we have two lines of descent from fully formed ancestors. What we would expect is a genetic barrior for changes, paritularly on a cellular level. The inclination would be to revert back to the original F1 wild type rather then morphological transitions.

#7 chance

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Posted 20 June 2005 - 02:13 PM

I’m voting for neither, as It is quite possible that life (or replicating molecules) developed more than once and either died out or became symbiotic and amalgamated with differing lineages.
However when we move on in time to single cells I think the line in the sand has been crossed, and we are all descended from one successful lineage.

#8 Raelian1

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Posted 21 June 2005 - 12:32 PM

Common ancestry (multiple or single) is a myth. There are similarities between a lot of organisms, but I wouldn't consider it a "common ancestry". My explanation is this, when the scientists created all life on Earth, they created the more complex animals (or plants) based on simpler animals (or plants). An example is, as the genetic engineers (creators) were creating inteligent humans like themselves, they started with a primate (probably a chimpanzee) and created various humanoids which we call cavemen and neanderthals. Eventually humans (like us) were created. A good analogy would be like taking a simple word processor program like Microsoft Notepad and making programming changes to it to eventually create Miocrosoft Word or Microsoft Works. These programs are more complex than Microsoft Notepad and that's how our creators created us by using DNA to program more complex animals. And we use the term "Common Ancestry" to denote this, but I think it's a mistake to use that term after all we can then say that Microsoft Word and Works has a "common ancestry" with Notepad.

#9 chance

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Posted 21 June 2005 - 02:14 PM

A good analogy would be like taking a simple word processor program like Microsoft Notepad and making programming changes to it to eventually create Miocrosoft Word or Microsoft Works. These programs are more complex than Microsoft Notepad and that's how our creators created us by using DNA to program more complex animals. And we use the term "Common Ancestry" to denote this, but I think it's a mistake to use that term after all we can then say that Microsoft Word and Works has a "common ancestry" with Notepad.

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So …. Our common ancestor is .... Bill Gates ! :o :)

#10 john_many_jars

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Posted 21 June 2005 - 03:11 PM

If only science worked this way.

But, alas, it doesn't. Conclusive evidence so rarely unmasks itself once a theory has been scrutinized for so long.

I know my life would be simpler if conclusive evidence would only show up on my doorstep just once.

#11 Mariner Fan

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Posted 21 June 2005 - 03:43 PM

Common ancestry (multiple or single) is a myth.


No, it is a scientific conclusion drawn from the data. The data will always be incomplete, but why should that stop science from drawing conclusions from what there is? Also, how can something be a myth if it is tentative?

There are similarities between a lot of organisms, but I wouldn't consider it a "common ancestry". My explanation is this, when the scientists created all life on Earth, they created the more complex animals (or plants) based on simpler animals (or plants).


Why would the scientists carry over broken genes and endogenous retroviruses?

A good analogy would be like taking a simple word processor program like Microsoft Notepad and making programming changes to it to eventually create Miocrosoft Word or Microsoft Works. These programs are more complex than Microsoft Notepad and that's how our creators created us by using DNA to program more complex animals. And we use the term "Common Ancestry" to denote this, but I think it's a mistake to use that term after all we can then say that Microsoft Word and Works has a "common ancestry" with Notepad.

View Post


Computer programs do not reproduce themselves. It is a poor analogy. Also, computer programs do not fit into a twin nested hiearchy like life on earth does. For example, the scientists could have made a half bat/half bird using genes from both mammals and birds. This would violate the twin nested hiearchy, but it is fully in the grasp of those who manipulate genetic systems.

#12 Phaedrus

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Posted 21 June 2005 - 06:04 PM

Meet the Consestors

"All roads lead to the origin of life. But because we are human, the path we shall follow will be that of our own ancestors. It will be a human pilgrimage to discover human ancestors. As we go, we shall greet other pilgrims who will join us in strict order, as we reach the common ancestors we share with them."

(The Ancestor's Tale, Richard Dawkins)

Richard Dawkin's book The Ancestor's Tale, tracks our ancestory all the way back to the single common ancestor. In this mythic journey he introduces us to 39 of our ancestors, the much celebrated transitional creatures on evolution's tree of life. I have an invitation for evolution enthusists. Let's take a journey though natural history starting with the human/chimpanzee split and finally arriving at the Eubacteria. What we will be looking at is what Dawkins called our consestors.

Obviously, a creationist like myself is highly skeptical of these consestors and considers them to be fairytale figments of the imagination. This is how it will work, assuming there is any interest. I describe the consestor and we can exchange our thoughts on the topic and move on to the next one.

I would be interested in the thoughts of evolutionists and creationists alike. It's only a 600 million year trip starting in the jungles of south Africa and going all the way back to the vast populations of our single celled consestors who emerged from the primordial soup. Any takers?

#13 chance

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Posted 21 June 2005 - 06:48 PM

Meet the Consestors

"All roads lead to the origin of life. But because we are human, the path we shall follow will be that of our own ancestors. It will be a human pilgrimage to discover human ancestors. As we go, we shall greet other pilgrims who will join us in strict order, as we reach the common ancestors we share with them."

(The Ancestor's Tale, Richard Dawkins)

Richard Dawkin's book The Ancestor's Tale, tracks our ancestory all the way back to the single common ancestor. In this mythic journey he introduces us to 39 of our ancestors, the much celebrated transitional creatures on evolution's tree of life. I have an invitation for evolution enthusists. Let's take a journey though natural history starting with the human/chimpanzee split and finally arriving at the Eubacteria. What we will be looking at is what Dawkins called our consestors.

Obviously, a creationist like myself is highly skeptical of these consestors and considers them to be fairytale figments of the imagination. This is how it will work, assuming there is any interest. I describe the consestor and we can exchange our thoughts on the topic and move on to the next one.

I would be interested in the thoughts of evolutionists and creationists alike. It's only a 600 million year trip starting in the jungles of south Africa and going all the way back to the vast populations of our single celled consestors who emerged from the primordial soup. Any takers?

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sounds interesting, count me in.

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Posted 21 June 2005 - 09:30 PM

Please ignore posts by raelian1.

#15 ninhursag

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Posted 22 June 2005 - 01:29 AM

Meet the Consestors



I would be interested in the thoughts of evolutionists and creationists alike. It's only a 600 million year trip starting in the jungles of south Africa and going all the way back to the vast populations of our single celled consestors who emerged from the primordial soup. Any takers?

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Yes, that would be very interesting. When will we start? :)

#16 Phaedrus

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Posted 22 June 2005 - 09:56 AM

This is what I have in mind, I'll post my discussion on consestor 1...39, I'll offer my take on whatever material I have for the discussion. You are free to respond as you see fit and then we can move on to the next one. I'll try to start out each post from Dawkin's book to prime the discussion and some of my thoughts on the subject. So lets get started:

Concestor 1

"Nevertheless, in our fantasy the chimpanzee pilgrims meet us in some Pliocene forest clearing, and their dark brown eyes, like or less predictable ones, are fixed on Concestor 1: their ancestor as well as ours. In trying to imagine the shared ancesotr, and obvious question to ask is, is it more like modern chimpanzees or modern humans, is it intermediate, or completely different from either?" (Dawkins, The Ancestor's Tale p. 101,102)

This question is being addressed at a level that is unlike any of the other transitions we will encounter on this journey. The genetic basis for it is largely unexplained, however, genetics is giving us a birds eye view of what would have had to occur. The human genome is now complete and it has made it possible to compare the genome sequences of apes like the chimpanzee. Scientists have determined the human chromosome 21 is the chromosome most responsible for are unique human features, particularly the development of higher cognitive funtions.

“Human–chimpanzee comparative genome research is essential for narrowing down genetic changes involved in unique human features, such as highly developed cognitive functions, bipedalism or the use of complex language. Here, we report the high-quality DNA sequence of 33.3 megabases of chimpanzee chromosome 22. By comparing the whole sequence with the human counterpart, chromosome 21, we found that:

1) 1.44% of the chromosome consists of single-base substitutions
2) 68,000 insertions or deletions. indels
3) These differences are sufficient to generate changes in most of the proteins.
4) 83% of the 231 coding sequences, including functionally important genes, show differences at the amino acid sequence level.
5) We demonstrate different expansion of particular subfamilies of retrotransposons between the lineages, suggesting different impacts of retrotranspositions on human and chimpanzee evolution.
6) The genomic changes after speciation and their biological consequences seem more complex than originally hypothesized.”
[italics mine]
Coding sequences:

“A total of 140 of these 179 genes show amino acid replacements… In contrast, 47 PTR22q (chimp chromosome 22) genes show significant structural changes affecting at least one of their transcript isoforms. Fifteen genes have indels within their coding region yet retain frame constancy”

DNA sequence and comparative analysis of chimpanzee chromosome 22

We have been told for decades that we are 98.5% identical to the chimpanzee and that this is iron clad proof of common ancestory. What was never taken into account was the presense of indels, which bumps the diversity up to around 95%. What is important to realize here is that not everything in the DNA strand codes for proteins (regulates or whatever), that is limited to about 2% of the entire genome. When you look at the coding sequences there are 15 gross structural changes which accounts for close to 20% of the coding sequences. What is even more supprising is that there are differences, at an amino acid sequences level in 83% of the 231 coding sequences.

How do evolutionists account for this? The short answer is, hundreds, if not thousands of mutations in hundreds, if not thousands of genes.

"For a long time, people have debated about the genetic underpinning of human brain evolution," said Lahn. "Is it a few mutations in a few genes, a lot of mutations in a few genes, or a lot of mutations in a lot of genes? The answer appears to be a lot of mutations in a lot of genes. We've done a rough calculation that the evolution of the human brain probably involves hundreds if not thousands of mutations in perhaps hundreds or thousands of genes -- and even that is a conservative estimate."

Evidence that human brain evolution was a special event

Here are a few of resources that I found helpful:

"Human evolution is characterized by a dramatic increase in brain size and complexity. To probe its genetic basis, we examined the evolution of genes in volved in diverse aspects of nervous system biology."

Accelerated Evolution of Nervous System

"A phylogenetic tree is a graphical means to depict the evolutionary relationships of a group of organisms. The phylogenetic tree below shows one reconstruction of the relationships among early human species, as we best know them today. It is a clickable image map."

Early Human Phylogeny

"The size of human brain tripled over a period of 2 million years (MY) that ended 0.2–0.4 MY ago. This evolutionary expansion is believed to be important to the emergence of human language and other high-order cognitive functions, yet its genetic basis remains unknown."

Evolution of the Human ASPM Gene, a Major Determinant of Brain Size

"Mutations can be caused by copying errors in the genetic material during cell division and by exposure to radiation, chemicals, or viruses, or can occur deliberately under cellular control during the processes such as meiosis or hypermutation."

Mutations

Anything from the chimpanzee/homo split is fair game. Obviously, I am interested in the genetic basis but for a timeline, the fossils are critical. Bear in mind that the other transitionals will not be anywhere near as complicated since they are not studied as much as this crucial period of natural history.

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Posted 22 June 2005 - 10:35 AM

How do evolutionists account for this? The short answer is, hundreds, if not thousands of mutations in hundreds, if not thousands of genes.

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The long answer is: it's much more complicated than that. I don't usually do this (and I may be risking a knuckle-rapping for it), but to introduce what I consider an important aspect of this, I'm going to save a little time by quoting from one of my own posts in another thread:

...there are two (very simplified) ways to look at the process. One is to consider the DNA to be using proteins to make cells, and the other is to consider the cells to be using the DNA to make proteins.

A nice metaphor for this is to consider what is contained in the DNA to be analogous to a list of words, and gene expression analogous to using words from the list to create a story. This idea goes a long way toward explaining why there is so much similarity in the genomes of organisms so dissimilar in morphology -- but it also helps in appreciating how vital to the process are the histories of the cells themselves, as components in the cellular colonies we refer to as: "organisms".  Just as English-speaking authors with personal histories as different as Mark Twain and Charles Dickens produce very different stories from (very nearly) the same words, cells with different histories produce very different protein structures from the same DNA.

But the history of a cell does not begin at the onset of embryonic development; that history includes the histories of all the cells of which it is only the latest in an unbroken succession reaching back to the origin of cellular forms [ ].

Not only is gene expression and the timing of expression as important or even more important than the gene sequence itself, which sequence gets expressed when is as much a function of the history of the cell in which the action is taking place as it is of anything on the DNA itself.

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#18 Phaedrus

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Posted 22 June 2005 - 01:02 PM

Calipithecus, now I have an analogy for you, think of the cell as a factory and the enzymes as the workers. I read something simular in an Anatomy and Physiology textbook. I take it you are familar with the process that unzips the DNA, creates the complimentary stands and transports them to the translation station in the ribosome. Here is a description of the process; enzymes

If DNA replication were a factory the workers would be the enzymes that run the machinery, handle the raw material, forge the material, inspect the product for discrepancies, repair deficient parts and, if need be, reject defective products and reclaim the raw material. During replication the DNA that has a three dimensional structure that we have become familiar with, the spiral of the double helix. During replication enzymes unwind the double helix into complimentary strand to form the messenger RNA (mRNA), the transportation RNA (mRNA) then moves it out of the nucleolus and sends it to the ribosome where it is translated into a protein. It is crucial that the mRNA template reading frame on the first codon be kept open, if it is not there will be a stop codon inserted which means it is defective and will not produce a functional protein. The material will end up being broken down and reclaimed (catabolic reaction) and this happens with clockwork precision.

What do you think happens to the reading frame when an indel is inserted?

This is why the genetic basis for this supposed transitional is still a mystery. Nothing like this has ever been directly observed or demonstrated in modern genetics.

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Posted 22 June 2005 - 04:06 PM

This is why the genetic basis for this supposed transitional is still a mystery. Nothing like this has ever been directly observed or demonstrated in modern genetics.

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I was with you right up to these last two sentences. Do you consider the 'supposed transitional' as somehow a special case genetically? I mean, the hypothetical concestor of chimps and humans is of particular interest to us for obvious reasons, but aside from that do you propose that (say) a frame shift is of greater significance in this case than in the case any other organism, real or hypothetical?

#20 Phaedrus

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Posted 22 June 2005 - 04:25 PM

I was with you right up to these last two sentences. Do you consider the 'supposed transitional' as somehow a special case genetically?  I mean, the hypothetical concestor of chimps and humans is of particular interest to us for obvious reasons, but aside from that do you propose that (say) a frame shift is of greater significance in this case than in the case any other organism, real or hypothetical?

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That is exactly what I am talking about, the expansion is the most dramatic morphological change since the cambrian explosion. There is a lot of research in this area and the gradual accumulation of minor changes does not begin to explain this.

"Varki points out that several major events in recent human evolution may reflect the action of strong selective forces, including the appearance of the genus Homo about 2 million years ago, a major expansion of the brain beginning about a half million years ago, and the appearance of anatomically modern humans about 150,000 years ago."

Human Brain Evolution Was a 'Special Event'

Given the enormous number of changes required for the expansion of the human brain in such a brief timeframe, I dare say, there isn't another transitional that even comes close. By the way, transitional, concestor and most recent common ancestor (mrca) are all pretty much the same thing.

As far as a frameshift, it is usually the result of an indel that causes the frame to shift producing a garbled protein. That is why a stop codon is usually inserted and what makes this even more dramatic is there are 68,000 of them when compared to our closest living relative, the chimpanzee. That include the 15 gross structural changes in the protein coding genes. It's all in the Concestor 1 post, trust me on that one. Try the link to the discussion on mutations.

Edited to add:

Here is a link that gives you examples of the effects of the various types of mutations:

http://users.rcn.com.../Mutations.html




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