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Author | Topic: Has natural selection really been tested and verified? | |||||||||||||||||||||||||||||||||
Admin Director Posts: 13038 From: EvC Forum Joined: Member Rating: 2.1 |
Hi RAZD,
Please let moderators handle the moderation issues. If you feel you are experiencing problems in discussion then please post to Report discussion problems here: No.2. Otherwise keep the focus on the topic.
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herebedragons Member (Idle past 885 days) Posts: 1517 From: Michigan Joined: |
Hi WK. I am new to this forum and have wanted to get involved with this discussion but havent had time to until now. After sifting through many argumentative and pointless posts, I feel you have some of the most knowlegable posts thats why I am directing this reply to you. I do not feel that the ToE is an adequate explaination as to the origins of life or the existance of life as we know it. I have no problem with "facts of evolution" (when they are indeed facts), what I have a problem with is when "theories of evolution" and "evolutionary history" is presented as fact. I am not suggesting that you or anyone else here has done that, that is just where I come from and why I want to understand some of the questions I have - so I can better make my own conclusions.
I think it is quite obvious that NS has been observed, tested, verified and can be accepted as a "fact of evolution". Where my problem lies is what the limits are that NS can accomplish. I used to think that one so called "boundary" would be speciation. My thinking was that once a species was reprodutively isolated NS could no longer come into play, since reproduction was no longer possible. A few posts that I have read since then, I realize that may be too simplistic. I still have some questions about that topic though. (maybe speciation should be a seperate thread, but since I am talking about it in context of NS ...)
Because a lot of 'species' classifications are based on old fashioned morphological or even simply geographic criteris, they aren't base on the actual establishment of reproductive isolation. Therefore what have been identified by taditional methods as distinct 'species' may still be considered to form part of one breeding population due to gene flow between different populations at hybridisation zones. I believe this quote was in reference to Galapogos finches and it appears to indicate that the individual 'species' may not actually be reproductively isolated. A quote from the article you cited(Grant and Grant, 2008): "Reproductive isolation in Darwin's finches appears to be entirely prezygotic as there is no evidence of genetic incompatibilities (Grant 1999)". I thought that would make them technically part of the same species. Can reproductive isolation and therfore speciation, be established on pre-mating barriers only? I thought there needed to be genetic incompatability. Could the Galapogos finches still be considered of the same "genetic" species? Do I understand this correctly: that these hybrdization 'zones' allow enough genes to be shared that it prevents the individual species from becoming genetically incompatable? Another question. Can genetic incompatability be established by DNA evidence alone? For instance if you compared the DNA from Geospiza fortis to that of Geospiza magnirostris, could the traits that makes the two species genetically incompatable (if they indeed are) be identified? I am curious as to what makes species genetically incompatable and if it is something that can be pointed to. My concern here is that if we do not have genetically incompatable 'species' it would call into question that NS could break that "barrier". From what I know, the same issues apply to the other examples cited - chichlids and peppered moths. What are your thoughts?
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi herebedragons, and welcome to the fray.
I do not feel that the ToE is an adequate explaination as to the origins of life ... You are likely to get a bunch of replies to this comment. The ToE does not attempt to explain the origins of life, that is a separate science called abiogenesis. Abiogenesis - Wikipedia
quote: This is a fairly new science, and there are a lot of unknowns involved in it. Suffice to say that at this point we don't know how or when life began, we just know that after some point at least 3.5 billion years ago that there is evidence of life. From that point to the present it appears that evolution is sufficient to explain the diversity of life.
... or the existance of life as we know it. I have no problem with "facts of evolution" (when they are indeed facts), what I have a problem with is when "theories of evolution" and "evolutionary history" is presented as fact. Theories are called theories because they are not facts, rather they are explanations of facts, with the best theories offering the best explanations. Theories can be validated but never proven, and are at best held as tentative approximations of reality until a better theory comes along. Theories are also falsifiable, which does not apply to facts, and the Theory of Evolution is falsifiable. Put briefly, the theory of evolution is that the process of evolution - the change in the frequency distribution of hereditary traits in breeding populations from generation to generation - is sufficient to explain the diversity of life as we know it. This can be falsified by demonstrating some part of the diversity of life that is not and cannot be explained by evolutionary processes. The complete sudden appearance of an entirely new type of life, for example.
Where my problem lies is what the limits are that NS can accomplish. What limits natural selection is two things: the ecology in question, and the hereditary traits available in the breeding population. NS doesn't create new features, it selects among the existing features in the breeding population of adult phenotypes the ones that are best adapted to survive and breed within the ecology.
My thinking was that once a species was reprodutively isolated NS could no longer come into play, since reproduction was no longer possible. A few posts that I have read since then, I realize that may be too simplistic. I still have some questions about that topic though. (maybe speciation should be a seperate thread, but since I am talking about it in context of NS ...) Indeed it could be a separate thread, however speciation is the point at which diversity in life begins, and this is part of Bolder-dash's revised topic (as far as I can determine), so I think a brief discussion is okay. Once populations become reproductively isolated, then evolution continues to occur, just within each breeding population rather than the (parent) super-population. Thus one daughter population will evolve through evolution (mutation, natural selection, etc) to adapt to its ecology, and the other daughter population will evolve (in a different way) through evolution (mutation, natural selection, etc) to adapt to its ecology, in much the same way that two different species will evolve differently.
I thought that would make them technically part of the same species. Can reproductive isolation and therfore speciation, be established on pre-mating barriers only? I thought there needed to be genetic incompatability. Could the Galapogos finches still be considered of the same "genetic" species? Again, the critical element is whether the populations are reproductively isolated. This isolation can occur pre-mating based on changes to mating behavior. In the Asian Greenish Warbler we see this behavioral isolation in effect: Greenish warblers
quote: Note that there is technically gene flow around the plateau, but in practical terms it takes generations for genes from one end to possibly reach the other end, and the probability of such flow is low, due to the reduced mating in the hybrid zones.
Do I understand this correctly: that these hybrdization 'zones' allow enough genes to be shared that it prevents the individual species from becoming genetically incompatable? Sometimes yes, sometimes no. It depends on the viability of the hybrids in question to act as go-betweens with fertile and fecund reproduction. Note too, that there are generally considered to be four forms of speciation events: Speciation - Wikipedia
quote: For instance if you compared the DNA from Geospiza fortis to that of Geospiza magnirostris, could the traits that makes the two species genetically incompatable (if they indeed are) be identified? I'm not sure if this has been done, but we do have samples of instances where genetic incompatibility has been observed to result following population isolation and subsequent evolution. Thus we know that genetic incompatibility does occur at some point in some cases of speciation. We also know that full incompatibility is not necessary. Take horses and donkeys and zebras as an example: they can form hybrids, but the hybrids are so rarely fertile\fecund that for all intents and purposes the gene flow is stopped with the deaths before reproduction of the hybrids.
My concern here is that if we do not have genetically incompatable 'species' it would call into question that NS could break that "barrier". Before we can talk about breaking a barrier, we would need to show that one exists. NS is opportunistic: it takes the opportunities provided by mutations and matches them to the opportunities provided by ecologies to select individual phenotypes that are best suited to survive and reproduce within the ecologies. As new mutations are added to the mix, more possibilities open up for evolution in general, and natural selection in particular, to take advantage of. By this means, an arm can develop into a wing, or a skin flap can develop into a gliding surface. We see from convergent evolution that similar adaptations to fit the same ecology can occur in diverse lineages.
Berkeley article on analogous features quote: If one of these can evolve from a placental squirrel, and the other evolve from a marsupial possum, then one has to wonder what kind of barrier can exist to block evolution. Enjoy.
ps ... as you are new here, some posting tips: type [qs]quotes are easy[/qs] and it becomes:
quotes are easy or type [quote]quotes are easy[/quote] and it becomes:
quote: also check out (help) links on any formatting questions when in the reply window. For other formatting tips see Posting Tips If you use the message reply buttons (there's one at the bottom right of each message):... your message is linked to the one you are replying to (adds clarity). You can also look at the way a post is formatted with the "peek" button next to it. Edited by RAZD, : ps we are limited in our ability to understand
by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
Hi Herebedragons,
You ask some good questions but I think this thread is already quite fragmented enough. Perhaps you could repost your questions in the existing Understanding the Genetics of Speciation thread? TTFN, WK
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Bolder-dash Member (Idle past 3658 days) Posts: 983 From: China Joined: |
I'm sure everyone agrees with you. You can't talk about evolution without mentioning random mutations. But you *can* talk about natural selection without mentioning mutations, and several people have attempted to explain this. That would be fine if I only said I wanted to talk about NS, but that is NOT what I said! I said I wanted to talk about natural selections effect on evolutionary change! That's a hard differentiation to make? You (and everyone else) are going to try to give me a lecture on biology because you can't see what I asked? (See what I mean about evolutionists really having a hard time pulling their eyes of of a microscope?) I have absolutely no interest to talk about NS as some generic reference to anything you choose to make it mean. You can do that in another thread. I started the thread and I said I wanted to talk about NS as it relates to EVOLUTION.! Percy, I really think it is disingenuous of you to allow this type of obfuscation to continue for so long. Seems I really touched a nerve with you evolutionists.
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herebedragons Member (Idle past 885 days) Posts: 1517 From: Michigan Joined: |
Thanks Razd. I guess I shouldn't have begun my post the way I did. I didn't mean to come across as ignorant of what the ToE is and isn't and what theories are and aren't. I was just trying to briefly state my reasons for coming to this forum.
By recomendation of Wounded King, I will take this discussion of speciation to the thread that he suggests. I believe you had a similar post on that thread. By the way, it was helpful, thanks. My second problem with NS is that it doesn't appear to always select the best trait for survival. By the definition of NS
Natural selection - the process that selects among the existing phenotypes of a species those that are best able to survive and breed, by the simple expedient of their survival and breeding within the ecology in question. This results in a descendant population with (a) a different frequency of hereditary traits from the parent population, and (b) a population that is better fit to survive and breed in the ecology in question. traits that improve the ability of the species to survive are selected for. And while I realize that it is somewhat speculative, I am not sure that traits we find in modern examples are always the most fit for survival. The example I am thinking of is bipedalism in humans. While we now consider bipdalism to be a significant advantage, I doubt our ancestors would have. Monkeys can climb trees, run and move faster, jump from branch to branch, and so on ... While walking on two legs would be a major hinderance. Especially to the first creatures to do so. Possibly pressure from predators was minimal, and our ancestor did not need to be able to escape? Could it have been as we developed tools we needed to be more upright? It is just that this is an example where NS appears to be going against the rules, so to speak. I don't really think that our ancestors stood up more and more (as I have read in some texts) and this drove the evolutionary change. NS says that the change is there in the population and is just selected on based on fitness for survival. So if they became more upright there was a distinct advantage to that change, based on survivability. Considering the amount of biological change that would need to take place to go from quadrapeds to bipeds, I think it is something that needs to be considered. And in my mind, it goes against the principle of NS. Any thoughts?
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Bolder-dash,
Please consider that if not one person here understands what you are trying to talk about, that the fault is in your failure to communicate what you want to talk about.
I started the thread and I said I wanted to talk about NS as it relates to EVOLUTION.! Does this mean that you want to talk about the effects of random mutations or not? Do you want to discuss first what evolution is, and then what natural selection means in that context? Or do you want to discuss first what natural selection is, and then how that fits into the context of evolution? Do you agree with this definition of evolution?
Evolution is the change in the frequency distribution of hereditary traits in breeding populations from generation to generation.
If not, why not? Do you agree with this definition of natural selection? Natural selection - Wikipedia
quote: If not, why not? Do you agree with the rest of the article as it continues
quote: Is there any part of that which you disagree with? What and why? See also the section on Evolution by means of natural selection - is this what you want to discuss? There is also a section that relates to speciation, the formation of new species and how natural selection contributes to this process. This is where diversity increases - is this what you want to discuss? Please give us something other than complaints to work with. I'm happy to discuss these things with you, but you need to lead the discussion with some idea of what you want to accomplish and what your expectations for resolution are. Enjoy. we are limited in our ability to understand
by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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RAZD Member (Idle past 1433 days) Posts: 20714 From: the other end of the sidewalk Joined: |
Hi again, herebedragons,
My second problem with NS is that it doesn't appear to always select the best trait for survival. By the definition of NS ... ...traits that improve the ability of the species to survive are selected for. And while I realize that it is somewhat speculative, I am not sure that traits we find in modern examples are always the most fit for survival. Part of the problem is that "survival of the fittest" is a misleading paradigm, and a better one would be "survival of the barely able" -- any individual that survives and breeds passes on their genes to the next generation, so just good enough is enough to pass the NS "test". Over time the more successful ones, if repeatedly tested will prevail in higher numbers, but the marginal ones will still be a part of the mix.
The example I am thinking of is bipedalism in humans.... It might be best to take this to another topic:
Evolutionary History of Apes is one that is open, and discusses ancient ancestors. See Message 18. Enjoy. we are limited in our ability to understand
by our ability to understand Rebel American Zen Deist ... to learn ... to think ... to live ... to laugh ... to share. • • • Join the effort to solve medical problems, AIDS/HIV, Cancer and more with Team EvC! (click) • • •
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Arphy Member (Idle past 4460 days) Posts: 185 From: New Zealand Joined:
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Hi Bolder-dash
This has gotten a bit complicated and I just want you guys to be on the same page, so maybe this works, or maybe not, I'm willing to give it a go.I am not an evo, but hopefully this definition sits alright with them (note, I am not trying to give a biology lesson, I am just trying to show some common ground). As such NS doesn't have any effect on evolutionary change (well, depends on what you mean by evolutionary change). If you mean "change" in organisms then this "change" occurs through mutations. If you mean "change" in ecosystems, then these changes are because of NS acting on organisms. So NS does not change a particular organism, but mutations do. NS selects whole genomes, It works with what is already there, it doesn't add anything new, it may "highlight" a feature of a group of organisms or "discriminate" against a feature but it doesn't actually change anything in the organisms themselves. So yes, i agree with the evos, NS and RM are completly different topics. They are both a vital parts in the general theory of evolution but as such are very different components. RM is about change in individual organisms, NS is about change in populations of organisms. The above alright? Maybe the last line was all that was needed. Not sure if everything was expressed fantasticly, but please let's find some common ground. I may be in disagreement with the evos here but, Coming back to your initial post I would say that evolutionists seem to portray RM and existing variation as the driver of the theory of evolution and NS is the driver of the General theory of evolution.
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Arphy Member (Idle past 4460 days) Posts: 185 From: New Zealand Joined: |
Hi RAZD
I was just looking at your definition of evolution and noticed something. Isn't "Evolution is the change in the frequency distribution of hereditary traits in breeding populations from generation to generation." really just a definition of Natural selection? I mean, this doesn't really make make any reference to variation or mutations at all? What is the difference between your definition for evolution and your definition for NS "Natural selection is the process by which heritable traits that make it more likely for an organism to survive and successfully reproduce become more common in a population over successive generations."? It seems to say the same thing except using different words. I mean "change in frequencey" is basically natural selection. Isn't it?
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ICANT Member Posts: 6769 From: SSC Joined: Member Rating: 1.6 |
Hi RAZD,
You quoted wikipedia where it says:
RAZD writes: Natural selection - Wikipedia
quote: This is how I thought you had explained this in another thread. Correct me if I get this wrong. I understand this to say that if you start with one species of finches with small beaks they would develop the large beaks over a period of time. But that is not what the study shows. That is why I was asking my question about what that test showed. It does not show the finches with small beaks developing large beaks from the small beaks, or the opposite way. It shows 14 different species of finches that have different size beaks and during wet times the small beak finches increase in number and the large beak finches decrease in number. In dry times the large beak finches increase in number and the small beak finches decrease in number. Now if that is evolution I am sold. Concerning Darwins finches wikipedia says: Darwin's finches - Wikipedia
quote:You can find some interesting information on the finches Here . God Bless, "John 5:39 (KJS) Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me."
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Peg Member (Idle past 4957 days) Posts: 2703 From: melbourne, australia Joined: |
Wounded King writes: The possible exception is in the form of pre-mating isolation in behavioral rather than genetic terms since some insular ethnic groups prefer to keep marriages within their own populations. But this is a social rather than a biological barrier. thats what im intersted in...biological barriers and the reason is because if it occurs among other species and if its a part of evolution, then it would surely happen among humans too
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Peg Member (Idle past 4957 days) Posts: 2703 From: melbourne, australia Joined: |
that was an entertaining read
and i mean that in all sincerity Edited by Peg, : No reason given.
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Coyote Member (Idle past 2134 days) Posts: 6117 Joined: |
thats what im intersted in...biological barriers
There are changes among the various human groups; the Human Races classes I took detailed a lot of these changes. and the reason is because if it occurs among other species and if its a part of evolution, then it would surely happen among humans too But none resulted in speciation; all human populations are of one species and fully capable of interbreeding. Religious belief does not constitute scientific evidence, nor does it convey scientific knowledge.
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Peg Member (Idle past 4957 days) Posts: 2703 From: melbourne, australia Joined: |
Coyote writes: There are changes among the various human groups; the Human Races classes I took detailed a lot of these changes. But none resulted in speciation; all human populations are of one species and fully capable of interbreeding. do you see speciation occuring any time soon and if it were to happen, what would be the precursor?
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