Freethought & Rationalism Archive

matty j · 01-08-2002, 11:25 PM

I have a feeling already that this post is going to somehow be twisted into a debate or give the wrong impression of myself to others, so I'm going to state my intentions as boldly and clearly as I possible can.

This post is not a mindless creationist post ignoring presently accepted data. Number one, I'm actually interested in hearing the answer. Number two, I'm not a creationist; the evidence for evolution is overwhelming. What I'm concerned with, as all real scientists are at this point, is with regards to the methodology of evolution, how it occurred. I suspect an answer to this question is out there, somewhere, but I have not heard it. It is, however, pivotal to the debate and my understanding of evolution (particularly 'macroevolution'), so it's more than worth mentioning.

In my mind, the distinction between microevolution and macroevolution is far more pronounced than most people like to admit. Whether the generalization I perceive is a result of dumbing things down to creationist level or my own misconceptions, I'll not speculate. Generally, I've seen it accepted in these debates that macroevolution is simply cumulative microevolution. That is to say, given that minor beneficial mutations occur, over time we could expect to see dramatic changes, and eventually the emergence of more complicated and significantly more fit organisms, like ourselves. I'll not debate this. That the structure of organisms could gradually change given naturally selective pressures and random mutations is, in most cases I've seen, very logical; it's even profound at times.

Where I see trouble is on the genetic level, where a more dramatic line has to be drawn between microevolution and macroevolution. Although the definition may be far different than this, in intention, the terms have always seemed to mean the separation between mutations which tinker with existing genetic material and mutations with *add* new genetic material. That microevolution, the tinkering with existing genetic material, happens is undeniable. I wouldn't even deny that, in the sense above (just looking at the structure of species that have emerged) that it might occasionally even equal macroevolution -- why shouldn't new organs and adaptations occur if the genetic material is there? However, there are limitations to this process, i.e. there's only so much genetic material to tinker with. You could not infinitely repeat the process of changing environments, having mutations and naturally selective pressures and turn a single-celled organism into a human: there isn't enough genetic material for microevolution to turn into macroevolution of that scale.

So, enter my definition of macroevolution, which would be the addition of new genetic material into the fold. I'll go over what I know so far on the subject, and how I feel it complicates things, at least as far as my current knowledge leads me to believe. Firstly, there are, of course, cases where DNA strands are errantly duplicated; I know that much. However, the examples I've been given of this happening seem neither beneficial -- ever -- or capable of occurring at the rate required for evolution process at the rate it has. There is, apparently, a fern that is tetra-something (or something like that), but that's not a very strong example (what about everything else), and the only other example of this sort of thing occurring I can think of is Down Syndrome, which is definitely not beneficial. There are, I expect, many more cases. I can guess already that the probability of this mutation, though, isn't near the 1 in 10000 commonly quoted for microevolutionary changes, and neither, I'd guess, would it be beneficial nearly as often, as there is an introduction of an entire strand into a previously functional cell -- the extra strand may be functional, but it's a significant amount of new coding, rather than just a simple change here or there. It's far more likely to make the cell metabolically instable -- it's not a small change.

So, I guess I'll get the questions. Am I missing something? Are these changes more common and/or more beneficial than I have been informed? Or is there another method that has somehow eluded my research (perhaps single nucleotides are added regularly, or perhaps alleles themselves are regularly copied and mixed in)?

Matty J

tronvillain · 01-08-2002, 11:51 PM

You don't have to resort to polyploidy to produce additional genetic material - consider <a href="http://www.cs.colorado.edu/~lindsay/creation/duplication.html" target="_blank">duplication mutations</a>. So, yes you have missed something.

[ January 09, 2002: Message edited by: tronvillain ]

CodeMason · 01-08-2002, 11:58 PM

For starters:
<a href="http://www.cs.colorado.edu/~lindsay/creation/duplication.html" target="_blank">http://www.cs.colorado.edu/~lindsay/creation/duplication.html</a>
<a href="http://www.gate.net/~rwms/EvoMutations.html" target="_blank">http://www.gate.net/~rwms/EvoMutations.html</a>

RufusAtticus · 01-09-2002, 12:39 AM

Hi Matty J.,

There is no genetic difference between microevolution and macroevolution. The modern synthesis showed that macroevolutionary differenerence are the result of the build up of microevolutionary differences. Here is something I wrote about "genetic barriers". Pay attention to the end where macro versus micro is discused.

Genetic Barriers Don't Exist

I've been reading some posts about the "genetic barrier" in another thread ("Thermodynamic challenge to creationists"). I figured I'd give the discussion its own thread. Now I know that some people will already know everything I say, but I'm saying it anyways. Perhaps someone will learn something.

I don't have the complete series of posts so I am unsure exactly what the "genetic barrier" is. I haven't seen any genetic evidence posted in the other thread to support such an idea. I also have never encountered such an idea before, and I am trained in genetics (BS in Genetics from UGA, currently studying for a PhD in Evolutionary Theory). All I can gather is that this barrier is proposed to "destroy" the foundation of evolution, but this barrier has no foundation of its own.

For starters, as I understand it, the genetic barrier hypothesis states, "there is a genetic barrier that prevents one *kind* from evolving into another *kind.*" I have yet to see any genetic, scientific justification for such a barrier. There clearly is not a justification because modern genetics has disproved this hypothesis. However, creationists still use the term because it allows them to look knowledgeable while actually knowing nothing. Such people have more negative ideas then positive ones.

The hypothesis of a "genetic barrier" was not originated by creationists. It arose almost a hundred years ago by biologists/evolutionists to describe the difference between macroevolution and microevolution. (For the sake of this argument, macroevolution is evolution appearing on the *super*-population level, and microevolution is evolution appearing on the *sub*-population level.) Creationists like to *claim* that the mechanisms from macroevolution are fundamentally different from the mechanisms for microevolution; this is their genetic barrier (from what I can tell). They then assert that there is no evidence for macroevolution while microevolution is well supported. They never show why any evidence supporting macro is wrong; they just say it is. A long quote (please forgive me) from Futuyma helps explains the issue:

Quote:

One of the most important tenets of the theory forged during the Evolutionary Synthesis of the 1930s and 1940s was that 'macroevolutionary' differences among organisms--those that distinguish higher taxa--arise from the accumulation of the same kinds of genetic differences that are found within species. Opponents of this point of view believed that 'macroevolution' is qualitatively different from 'microevolution' within a species, and is based on a totally different kind of genetic and developmental repatterning. The iconoclastic geneticist Richard Goldschmidt (1940), who held this opinion, believed that the evolution of species marks the break between 'microevolution' and 'macroevolution'--that there is a 'bridgeless gap' between species that cannot be understood in terms of the genetic variation within species. Genetic studies of species differences have decisively disproved Goldschmidt's claim. Differences between species in morphology, behavior, and the process that underlie reproductive isolation all have the same genetic properties as variation within species: they occupy consistent chromosomal positions, they may be polygenic or based on few genes, they may display additive, dominant, or epistatic effects, and they can in some instances be traced to specifiable differences in proteins or DNA nucleotide differences. The degree of reproductive isolation between populations, whether prezygotic or postzygotic, varies from little or none to complete. Thus, reproductive isolation, like the divergence of any other character, evolves in most cases by the gradual substitution of alleles in populations. (Evolutionary Biology, third edition. 477-478)

Barrierists believe, like Goldschmidt did, that macroevolution and microevolution are fundamentally different; however, unlike Goldschmidt, they use the absence of a macro-only mechanism as proof of a creator and proof against evolution. The reason for the absence of a macro-only mechanism is that the same mechanisms apply to both micro- and macroevolution. This is not an *easy out* explanation as they'd have laymen believe. It is backed up by genetic and biological observations and experiments. Goldschmidt was able to state his claim in 1940 because the science of molecular genetics did not exist then. It wasn't until the 1950s that Watson and Crick solved the structure of DNA and showed how genetic information was passed in cell division via template strands. The genetic code was later solved, explaining how DNA encoded proteins. Modern sequencing strategies allow us to map molecular genetic mutations to actual genes, demonstrating the variability of populations and the power of evolution. These sequencing strategies also allow us to map the differences between two organisms' genomes. The genetic distinctions for taxa can be detected by comparing organisms from different taxa. The data generated from such investigations show that distinctions between taxa follow the same rules as distinctions within a taxon.

<a href="http://www.talkorigins.org/origins/postmonth/jul01.html" target="_blank">http://www.talkorigins.org/origins/postmonth/jul01.html</a>

Also check out these pages: <a href="http://www.talkorigins.org/faqs/macroevolution.html" target="_blank">http://www.talkorigins.org/faqs/macroevolution.html</a>
<a href="http://www.talkorigins.org/faqs/modern-synthesis.html" target="_blank">http://www.talkorigins.org/faqs/modern-synthesis.html</a>

[ January 09, 2002: Message edited by: RufusAtticus ]

liquid · 01-09-2002, 02:43 AM

I'd like to pick up on your comment that you could not find a beneficial example of polyploidy (The duplication of chromosomes).

This is an extremely useful mutation for infertile hybrids of many kinds. You see, many hybrids cannot reproduce as their gametes (sexual cells, like sperms and eggs) cannot split the odd number of chromosomes between them. What chromosome multiplication allows some of them to do is breed and form a viable new species. That's particularly beneficial from a Darwinian point of view! Without it, you don't even get off the starting line.

Example 1: While studying the genetics of the evening primrose, Oenothera lamarckiana, de Vries (1905) found an unusual variant among his plants. O. lamarckiana has a chromosome number of 2N = 14. The variant had a chromosome number of 2N = 28. He found that he was unable to breed this variant with O. lamarckiana. He named this new species O. gigas.

Example 2 : Wenby (1950) demonstrated that two species in this genus were produced by polyploidization from hybrids. He showed that Tragopogon miscellus found in a colony in Moscow, Idaho was produced by hybridization of T. dubius and T. pratensis. He also showed that T. mirus found in a colony near Pullman, Washington was produced by hybridization of T. dubius and T. porrifolius. Evidence from chloroplast DNA suggests that T. mirus has originated independently by hybridization in eastern Washington and western Idaho at least three times (Soltis and Soltis 1989). The same study also shows multiple origins for T. micellus

There are loads more on <a href="http://www.talkorigins.org/faqs/faq-speciation.html" target="_blank">http://www.talkorigins.org/faqs/faq-speciation.html</a>
section 5.1

[ January 09, 2002: Message edited by: liquid ]

butswana · 01-09-2002, 05:47 AM

The "micro-macro" thing is just more bullshit from creationists. They started using it so that they could concede on the points of observed changes(moths and dogs)(micro), while denying speciation(macro).

CodeMason · 01-09-2002, 06:03 AM

The micro/macro difference, I believe, is simple.
Micro is natural selection on pre-existing alleles (ie. no mutation).
Macro is mutation + micro.

Of course thousands of beneficial mutations have been observed, so it is, as you say, bullshit.

01-08-2002, 11:25 PM	#1
matty j Junior Member Join Date: Jan 2002 Location: Guelph, Ont. Posts: 8	Question I have a feeling already that this post is going to somehow be twisted into a debate or give the wrong impression of myself to others, so I'm going to state my intentions as boldly and clearly as I possible can. This post is not a mindless creationist post ignoring presently accepted data. Number one, I'm actually interested in hearing the answer. Number two, I'm not a creationist; the evidence for evolution is overwhelming. What I'm concerned with, as all real scientists are at this point, is with regards to the methodology of evolution, how it occurred. I suspect an answer to this question is out there, somewhere, but I have not heard it. It is, however, pivotal to the debate and my understanding of evolution (particularly 'macroevolution'), so it's more than worth mentioning. In my mind, the distinction between microevolution and macroevolution is far more pronounced than most people like to admit. Whether the generalization I perceive is a result of dumbing things down to creationist level or my own misconceptions, I'll not speculate. Generally, I've seen it accepted in these debates that macroevolution is simply cumulative microevolution. That is to say, given that minor beneficial mutations occur, over time we could expect to see dramatic changes, and eventually the emergence of more complicated and significantly more fit organisms, like ourselves. I'll not debate this. That the structure of organisms could gradually change given naturally selective pressures and random mutations is, in most cases I've seen, very logical; it's even profound at times. Where I see trouble is on the genetic level, where a more dramatic line has to be drawn between microevolution and macroevolution. Although the definition may be far different than this, in intention, the terms have always seemed to mean the separation between mutations which tinker with existing genetic material and mutations with add new genetic material. That microevolution, the tinkering with existing genetic material, happens is undeniable. I wouldn't even deny that, in the sense above (just looking at the structure of species that have emerged) that it might occasionally even equal macroevolution -- why shouldn't new organs and adaptations occur if the genetic material is there? However, there are limitations to this process, i.e. there's only so much genetic material to tinker with. You could not infinitely repeat the process of changing environments, having mutations and naturally selective pressures and turn a single-celled organism into a human: there isn't enough genetic material for microevolution to turn into macroevolution of that scale. So, enter my definition of macroevolution, which would be the addition of new genetic material into the fold. I'll go over what I know so far on the subject, and how I feel it complicates things, at least as far as my current knowledge leads me to believe. Firstly, there are, of course, cases where DNA strands are errantly duplicated; I know that much. However, the examples I've been given of this happening seem neither beneficial -- ever -- or capable of occurring at the rate required for evolution process at the rate it has. There is, apparently, a fern that is tetra-something (or something like that), but that's not a very strong example (what about everything else), and the only other example of this sort of thing occurring I can think of is Down Syndrome, which is definitely not beneficial. There are, I expect, many more cases. I can guess already that the probability of this mutation, though, isn't near the 1 in 10000 commonly quoted for microevolutionary changes, and neither, I'd guess, would it be beneficial nearly as often, as there is an introduction of an entire strand into a previously functional cell -- the extra strand may be functional, but it's a significant amount of new coding, rather than just a simple change here or there. It's far more likely to make the cell metabolically instable -- it's not a small change. So, I guess I'll get the questions. Am I missing something? Are these changes more common and/or more beneficial than I have been informed? Or is there another method that has somehow eluded my research (perhaps single nucleotides are added regularly, or perhaps alleles themselves are regularly copied and mixed in)? Matty J

01-08-2002, 11:51 PM	#2
tronvillain Veteran Member Join Date: Oct 2000 Location: Alberta, Canada Posts: 5,658	You don't have to resort to polyploidy to produce additional genetic material - consider <a href="http://www.cs.colorado.edu/~lindsay/creation/duplication.html" target="_blank">duplication mutations</a>. So, yes you have missed something. [ January 09, 2002: Message edited by: tronvillain ]</p>

01-09-2002, 02:43 AM	#5
liquid Veteran Member Join Date: Jan 2001 Location: UK Posts: 1,440	I'd like to pick up on your comment that you could not find a beneficial example of polyploidy (The duplication of chromosomes). This is an extremely useful mutation for infertile hybrids of many kinds. You see, many hybrids cannot reproduce as their gametes (sexual cells, like sperms and eggs) cannot split the odd number of chromosomes between them. What chromosome multiplication allows some of them to do is breed and form a viable new species. That's particularly beneficial from a Darwinian point of view! Without it, you don't even get off the starting line. Example 1: While studying the genetics of the evening primrose, Oenothera lamarckiana, de Vries (1905) found an unusual variant among his plants. O. lamarckiana has a chromosome number of 2N = 14. The variant had a chromosome number of 2N = 28. He found that he was unable to breed this variant with O. lamarckiana. He named this new species O. gigas. Example 2 : Wenby (1950) demonstrated that two species in this genus were produced by polyploidization from hybrids. He showed that Tragopogon miscellus found in a colony in Moscow, Idaho was produced by hybridization of T. dubius and T. pratensis. He also showed that T. mirus found in a colony near Pullman, Washington was produced by hybridization of T. dubius and T. porrifolius. Evidence from chloroplast DNA suggests that T. mirus has originated independently by hybridization in eastern Washington and western Idaho at least three times (Soltis and Soltis 1989). The same study also shows multiple origins for T. micellus There are loads more on <a href="http://www.talkorigins.org/faqs/faq-speciation.html" target="_blank">http://www.talkorigins.org/faqs/faq-speciation.html</a> section 5.1 [ January 09, 2002: Message edited by: liquid ]</p>

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01-08-2002, 11:58 PM	#3
CodeMason Regular Member Join Date: Feb 2001 Location: Australia Posts: 226	For starters: <a href="http://www.cs.colorado.edu/~lindsay/creation/duplication.html" target="_blank">http://www.cs.colorado.edu/~lindsay/creation/duplication.html</a> <a href="http://www.gate.net/~rwms/EvoMutations.html" target="_blank">http://www.gate.net/~rwms/EvoMutations.html</a>

01-09-2002, 05:47 AM	#6
butswana Veteran Member Join Date: Sep 2001 Location: Indianapolis, IN Posts: 1,804	The "micro-macro" thing is just more bullshit from creationists. They started using it so that they could concede on the points of observed changes(moths and dogs)(micro), while denying speciation(macro).

01-09-2002, 06:03 AM	#7
CodeMason Regular Member Join Date: Feb 2001 Location: Australia Posts: 226	The micro/macro difference, I believe, is simple. Micro is natural selection on pre-existing alleles (ie. no mutation). Macro is mutation + micro. Of course thousands of beneficial mutations have been observed, so it is, as you say, bullshit.

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