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Author Topic:   Definition of Species
herebedragons
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Joined: 11-22-2009
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Message 25 of 450 (537633)
11-29-2009 9:02 PM
Reply to: Message 24 by RAZD
11-28-2009 3:02 PM


Re: for herebedragons - speciation, definition first, discussion second
Razd - thank-you. finally a good response from someone! I actually found it by accident as I was looking for another topic since that thread was going nowhere but a bar brawl I will respond after I have time to read the post and the materials carefully.
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herebedragons
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Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 35 of 450 (539991)
12-21-2009 12:23 PM
Reply to: Message 24 by RAZD
11-28-2009 3:02 PM


Re: for herebedragons - speciation, definition first, discussion second
Hi Razd - I have finally been able to spend some time on this and post a response. I also found several other threads on similar subjects and have read through them. So here are my thoughts, observations, ponderings, questions, etc.:

First of all, I see defining a species is very subjective and difficult to nail down precisely, since there is no one "perfect" rule to apply. It seems to me that it is important define species accurately and with a fair amount of precision. Someone commented that species is the only thing that matters in an ecosystem, but a deeper, more accurate understanding of species and what makes them different would help us understand how life has developed and why.


{ramble}
Wouldn't it be easier to use genetics to define a species similar to the morphological definition, as "a population of individual organisms with 99% identical DNA" for instance?
What about: "a species is a population of individual organisms with similar hereditary traits in common, separated from other species by different hereditary traits and biological barriers preventing breeding."
In both cases it comes down to how much needs to be the same and how much needs to be different to differentiate one species from another.
{/ramble}

I wasn't sure what you were meaning by this (the {ramble} part made it confusing what your intention was), but yeah, maybe in some ways it would be more accurate to classify organisms that way, although the amount of work involved would certainly not make it "easier". And, as you pointed out, it still comes down to subjectivity - "how much needs to be the same and how much needs to be different?"


We also see with horses, donkeys and zebras, that there is a genetic barrier to hyridization that has occurred since they separated from a common ancestor, one that results in infertile or poorly fertile offspring that most ofted die without reproducing, thus demonstrating genetic reproductive isolation being acquired.


That is similar to the genetic species concept in Message 1, using one specific gene. I think I'd want to do some kind of cladistic analysis of more units, perhaps at a chromosome level, and then focus on the one showing the most difference to provide the cutoff information.
This would have to be done first for species that are closely related but just not breeding compatible -- horses/zebra/donkey and whitetail/mule deer -- to see what a genetic level of difference was necessary.

This hasn't been done? Kinda surprising that it hasn't.

Obviously, the fossil record becomes even more imprecise and speculative and subject to error.


Part of the problem is the degree of dis-similarity that can occur in a species, whether you are a lumper or a splitter, and how good the evidence. Add the ego-boost of being able to describe a new species fossil for the first time, and you can see that defining species for fossils can be a problem.

Not that this is definitively wrong, we need to be able to categorize them in some way - in the best way we know how. But there are just too many unknowns in the fossil record to be certain that species are categorized correctly. For example, the marsupial flying squirrel and the placental squirrel example you gave me. If fossils were found of these animals they would most likely be considered very similar animals. Like wise the Tasmanian wolf and common grey wolf would be thought to be very close cousins. However, we know they are very different animals. Similarly, if fossils for a Saint Bernard and a Chihuahua were found they would certainly be classified as quite unrelated, however we know them to be of the same species. (maybe Saint Bernard and Chihuahua aren't great examples because I can't imagine them actually breeding in the wild - or in captivity for that matter ) But, if these types of situations could be known in the fossil record, it would quite probably completely uproot the entire evolutionary tree, or at least break some major branches. I know that this a "what if" situation and not something we can plausibly test because soft tissue is rarely preserved and we have virtually no way of knowing for sure whether fossilized species were reproductively isolated or not. But, never-the-less, I see it as a real possibility that there would be many such instances. There is just too much we can't know about the fossil record.

Secondly, I realized that I was actually trying to define "kind" and I now see that it is just not that simple. Our observations in nature don't seem to match up to any idea of a kind. But I am thinking it is important how we classify organisms.

I see you are a fan of cladistic classification. Doesn't this system assume common ancestry? What I mean is you may have sufficient evidence that a horse and a zebra have a common ancestor, but is there that degree of certainty for all known species. Where would you put species that were uncertain? Would they be left out or placed in an approximate or assumed clade? Would it be noted that they were uncertain until sufficient evidence was presented? I do need to have a better understanding of cladistics, so I'm not drawing conclusions, just questioning.

A newer system of classification I found some information on is Baraminology. You probably have already looked at it and drawn your own conclusions but here is the link:

http://www.christiananswers.net/q-crs/baraminology.html

It is a system of classification that some are trying to develop. It is highly criticized and considered to be junk science. But, all the criticism I read was in regard to their conclusions and starting assumptions not the actual data or the "science" they were doing. This is a very new line of research and I would think it should be given a chance, unless there are fundamental flaws in how they do the research.

This quote:

quote:
Some creationists have tried to reprove me for accepting too much evolution. To this I can only respond with the results of my research. I have no preconceived notion of how much evolution could or could not occur. In fact, when I began baraminology research, I expected to find very narrow baramins, at most a few genera in each. I could not find evidence to support that view, so I changed my position. If future work showed discontinuity at the level of genus or even species, I would accept that result also. On the other hand, if I found continuity between different mammalian orders, I would accept that result.

http://www.creationresearch.org/.../43/43_3/baraminology.htm

gives some degree of confidence that they are willing to base their conclusions on the data and not pre-conceived notions (whether they do what they say is another matter). You could say that they believe in creation is a pre-conceived notion. But I would also include that I feel evolutionists base their conclusions on the fact that they believe evolution to be true. Its all a matter of perspective - but, I guess that's a discussion for another thread.

Their research has confirmed equid fossil series is a legitimate example of species evolution. This is a series that creationists have long been critical of. They have also verified the evolution of the subtribe Flaveriinae. The problem is that he interprets both cases as post-flood diversification. So not only did he say the "f" word, but the biblically implied <6000 years since the flood is considered insufficient for such evolution to occur. First of all, I personally am not convinced that the bible really says that the flood occurred <6000 years ago, but that is the position of most creationists. But that too is a different discussion. And secondly, the possible explanation for the rapid transformation of C3 to C4 photosynthesis that was presented was that the information for the C4 pathway was already contained in the DNA code and was turned on like a switch by some stimulus. This makes much more sense to me personally than gradualism. I would like to discuss this idea a bit later. Here is a quote from Woods:

quote:

Related to accepting "too much evolution" is the objection that there is no mechanism capable of producing intrabaraminic diversity in the short chronology (<6000 years) implied by the Bible. I agree completely (Wood, 2002b; Wood and Murray, 2003), but I do not believe that this is a legitimate argument against baraminology. Demanding a mechanism seems to be a prerequisite for acceptance among scientists, but it is not always necessary or even prudent.

A mechanism for Darwin's theories was not known for what, 50 years after his publication of Origin of Species, when DNA was discovered. Yet his theories weren't arbitrarily thrown out.

So, could you give me a brief overview of your opinion of Baraminology and an idea of where I can find some objective information on the subject? One problem with the debate between creation and evolution is it is so polarizing. There just doesn't seem to be a neutral side. It's one or the other.

Anyway, I think it is good and beneficial to our understanding of life that we are exploring different ways of classifying and identifying organisms. With our ever increasing understanding of how complex and interconnected life is, we need better and more accurate ways to identify, at the very basic level, species.


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 37 of 450 (540040)
12-21-2009 6:44 PM
Reply to: Message 36 by Dr Jack
12-21-2009 1:36 PM


Re: for herebedragons - speciation, definition first, discussion second
Yes, Mr.Jack, I am sure they could and I certainly didn't mean to imply that a trained palaeontologist couldn't do their job. But those particular examples are modern specimens and I wasn't meaning that we find modern specimens that we know what the differences in structures should be. I was using it as an example of the information that is missing from the fossil record. Scientists regularly debate as to how to classify a fossil specimen and often ultimately disagree. It is not easy to classify fossils for the very reason I cited - missing information. But your point about not just looking a crude morphology was well taken.

Thanks

Edited by herebedragons, : No reason given.


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 38 of 450 (540120)
12-22-2009 10:29 AM
Reply to: Message 36 by Dr Jack
12-21-2009 1:36 PM


Re: for herebedragons - speciation, definition first, discussion second
Mr. Jack, I have some more evidence to support my statement.

quote:
If the bones of a fossil animal are the same as those of an extant form classified as a marsupial, then one can confidently classify the fossil type as a marsupial. But such is not the case when a fossil form is now extinct. R. A. Barbour, an expert on marsupial anatomy, says "the marsupial skeleton is essentially mammalian and has few unique features present in all species."

Even among living mammals, traits typical of marsupials are not found in every kind of marsupial ... Therefore, when we look at the fossil remains of an extinct animal, we cannot be certain the bones in question are those of a marsupial. Even on the basis of soft anatomy, Marsupialia is a rather poorly defined category ... And yet, when remains of extinct mammals are discovered in regions where marsupials predominate today (e.g., Australia and New Guinea), or are assumed to have predominated in times past (South America), it is often assumed the fossils in question are those of marsupials. Mammalian specimens found outside those regions are typically categorized as placental.

(edited for length)


http://www.macroevolution.net/marsupials.html

Again, my primary point was the difficulty of categorizing extint fossil specimens accurately. So, clearly, there is a large amount of uncertainty in the fossil record.

Thanks


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 41 of 450 (540155)
12-22-2009 2:13 PM
Reply to: Message 24 by RAZD
11-28-2009 3:02 PM


Re: for herebedragons - speciation, definition first, discussion second
Belief that the term species and other taxonomic categories represent real distinctions in nature and not just subjective divisions for human convenience is difficult to pin down and defend with any certainty.
quote:
the apparent need for a pluralistic species concept raises the question of whether there is indeed anything "real" about species. If different examples of species require different causes and different definitions, then maybe our intuition that "a species is a species is a species" is misleading. It may be just an arbitrary convenience after all, and we should be separately distinguishing "phenetic species" and "reproductive isolation species" and "mate recognition species".and "ecological species" and "cladistic species" without any implication that they are all, somehow, the same thing.

http://www.zoology.siu.edu/king/304/species.htm#15.3

Although the most popular and widely excepted definition seems to be the Biological species concept,

This concept states that "a species is a group of actually or potentially interbreeding individuals who are reproductively isolated from other such groups."

but both speciation and reproductive isolation remain problematic issues. "Reproductive isolation", widely considered an essential ingredient in defining the word species, is itself vaguely and inconsistently defined. Exactly when does reproductive isolation occur? what are the actual mechanisms that bring it about? is geographic isolation enough to develop reproductive isolation? what does “potentially” interbreeding individuals actually mean? etc. Truly “reproductive isolation” is quite ill defined.

quote:
"Despite more than a century of deliberation on the origin of species, evolutionary biologists remain undecided as to the mechanisms by which reproductive isolation is generated. Whether geographic isolation, or allopatry, is a prerequisite to speciation has been hotly debated ..., and there is is not even consensus as to the nature of the reproduction isolation that accumulates in allopatric populations" (Zoology 304)

Then throw into the mix hybridization. If you fail to observe interbreeding in a given case, is it safe to assume there no members of the population that do not interbreed? It is possible that interbreeding does occur at some place other than what has been observed or that it may occur at some other time? There are numerous cases of forms that are treated as separate species and were not previously known to hybridize but are now know to do so.

Some examples here:
http://www.macroevolution.net/reproductive-isolation.html

The author gave an analogy that I think clearly illustrates the problem and also the problem of presupposing or historically considering a form to be a separate species despite there ability to interbreed as are the Spanish sparrow (P. hispaniolensis) and the house sparrow [P. domesticus].

quote:
If it were widely supposed that an animal could not be a dog if it had fleas, then it would be hard to show that dogs often do have fleas. For suppose everyone agreed a particular animal was a dog and someone subsequently discovered that it had fleas. The discovery would be to no avail because as soon as it was announced everyone would say "That is not a dog! Dogs do not have fleas!" Since in everyone's estimation the animal would no longer be a dog, everyone would be free to go on believing dogs do not have fleas. Such would be the case even if most, or even all unexamined dogs were heavily infested with fleas. (Eugene M. McCarthy, Ph.D.)

It seems to me the concept of species is very illusive and there is no “one size fits all approach”. In addition, I’m not sure it has any value in the real world other than for our convenience in discussing different animals. IOW when I say ‘zebra’ you know I am talking about an animal that lives in Africa and has black and white stripes and when I say ‘horse’ you know I am talking about a domesticated animal that is primarily used for human recreation. Whether they are clearly distinct species may be irrelevant. The problem with a statement like that, from an evolutionist’s point of view, is that if a species distinction is irrelevant, that kinda makes speciation irrelevant too, since after speciation occurs the results would be irrelevant.

penstemo writes:
DNA testing is the way of the future, I believe, for both plants and animals.

I have been doing some reading about DNA sequence analysis and feel there is a lot of promise to resolve some of these problems and give us a clearer picture of lineage and thus history, but I have a feeling evolutionists (specifically gradualists) and creationists alike are going to be disturbed by the results. Any other input on DNA sequencing would be helpful as I know very little about the terminology or theory behind it.

Good Day All


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 43 of 450 (540167)
12-22-2009 2:50 PM
Reply to: Message 39 by Dr Jack
12-22-2009 10:49 AM


Re: Quality sources

Please use credible sources as opposed to crank websites.
I particular like the way your source neatly elides the difference between "few" and none, and the differences common to all marsupials and features that can be used to distinguish marsupials - that quality quote mining.

My apologies, Mr. Jack, but what consitutes a "credible" source as opposed to a "crank website"? I am avoiding "creationist" sites as they are "crank" or "bogus". But this was not a creationist site. I don't believe I quoted anything out of context. I did edit some content because I felt it was unnecessary to the discussion and sorta lengthy. So I don't see how I am guilty of quote mining. I looked over the entire site, and the author appeared to be credible, at least as credible as I could determine. So what is a "credible" source? Does it have to agree with popular or prevalent ideas?

I will concede the point regarding distinguishing marsupials, as it is actually irrelevant to the disscussion, but would like clarification on "credible". I am trying to be a responsible and thoughtful part of this forum and don't feel that I am just spouting nonsense that is "cut and pasted from creationist propaganda".

Thanks


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 Message 39 by Dr Jack, posted 12-22-2009 10:49 AM Dr Jack has responded

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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 44 of 450 (540174)
12-22-2009 3:20 PM
Reply to: Message 42 by Coyote
12-22-2009 2:21 PM


Re: Baraminology

It is not a field of research because no conclusions can be arrived at other than those specified in scripture. It is pure religious apologetics.

Thanks Coyote, but thats the criticsm I've already heard. I don't think scripture puts a huge "restaint" on the research though as there are very few "types" actually described. That man is a seperate "type" seems to be the most problamatic for evolutionists. I was hoping there would be something a bit more condemning, like "they don't wear gloves when they handle evidence." lol

The scripture only sets the outer boundaries, not the entire realm of possible conclusions they could arrive at. So I'm not sure it's fair to say "no conclusions" because scripture really doesn't draw too many conclusions on it's own. For instance, the horse evolution series and the subtribe Flaveriinae both confirmed evolution. I'm sure many a creationist will be uneasy about those conclusions.

Creationists are constantly being asked to define what a "kind" is. I personally am not sure it is really necessary or practical or maybe even possible, but if a group of creationists are attempting to come up with a definition, maybe their work should be based on the data, not on the fact they are trying to define "kind".

Thanks


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


(1)
Message 49 of 450 (540286)
12-23-2009 10:17 AM
Reply to: Message 48 by Blue Jay
12-22-2009 5:50 PM


Re: Baraminology
Hi Bluejay

It's good to read true open-mindedness for a change!

Wow! Thanks. I think that is just about the highest compliment I could hope to receive on a site like this. I do believe that God created life and that the Bible is true. However, I don’t think that the Bible needs to be translated literally word for word true. One thing the Bible teaches is that God is a God of truth. Why then, would the observed evidence be deceptive or untrue? That is why I came to this forum, to discuss my doubts and concerns with evolution and creation alike. I want to gain knowledge and understanding of this incredibly complex and beautiful world in which we live in (that’s something both creationist and evolutionist can agree on). I think your comment

Libeling ideology runs the risk of making one's own argument appear just as ideological in nature.

is spot on and contributes to meaningless and fruitless arguments (on both sides). I personally am trying to avoid this type of debate and stick to what is beneficial to my better understanding of life.

Well, that’s my ideological rhetoric for the day. lol.

So, what are the empirical reasons for suspecting that evolution can only go so far?

I suppose it is the same type of reasons that scientists are investigating abiogenesis - we want to understand the beginnings. Did life come from a few created types or “kinds” or did we come from a protein “soup”. Both ideas are equally ideological and theoretical in nature. Yet, abiogenesis has the “advantage” of being a naturalistic solution and therefore, empirical.

I am not trying to build a case in favor of Bariminology, but I do question the seemingly off-handed dismissal of anything that goes against mainstream science. So many scientific breakthroughs were based on concepts that went against “conventional” thought.

But, at this point I think I have an opinion on Baraminology similar to yours:

As a lifelong Christian, I would be very interested if such data were uncovered, but I cannot honestly characterize the basis of the field of baraminology as anything greater than wishful thinking, so I am required by my personal sense of integrity to reject it as a legitimate academic pursuit. Maybe the future will change my mind, I'm not sure, but my skepticism for that is currently very high.

The problem is that since their research is rejected by mainstream science, no matter what their findings are, they are going to be dismissed. You’ll never see a program on Discovery Channel called “Scientists Prove the Existence of Biblical Kinds” because they are not doing anything “scientific” nor are they "scientists".

Thanks


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 50 of 450 (540294)
12-23-2009 10:52 AM
Reply to: Message 46 by Dr Jack
12-22-2009 5:17 PM


Re: Quality sources
Fair enough. I do try to check my sources to be sure they are credible, but it's not always easy. I would also like to point out that just because a source is "crank" doesn't mean there is no useful information from that source, one would just need to use more caution when accepting information as fact. Also I would note it is quite diffucult to argue a contrary position using the same sources as everyone else, and that's kinda the point of this forum, to discuss conflicting points of view. So, personally, I would prefer to be told "That is not credible information because ..."

In this case, I really wasn't trying to argue about marsupial identification, but merely trying to point out the difficulties of defining the concept of species. What are your thoughts about our ability to define and identify the concept of species with a significant amount of accuracy and precision?

Thanks

Edited by herebedragons, : No reason given.


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 Message 46 by Dr Jack, posted 12-22-2009 5:17 PM Dr Jack has responded

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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 55 of 450 (540358)
12-24-2009 7:39 AM
Reply to: Message 52 by Blue Jay
12-23-2009 7:57 PM


Re: Off-handed dismissal
This makes me a bit curious: what makes the dismissal of baraminology by mainstream science seem off-handed to you?

It seemed off-handed before your's and coyote's explainations. I should have said 'did' instead of 'do'. I do not really hope or expect that their work will have any real impact - partially because I think they are traveling down a dead end, or at least an end that has no hope of being resolved satisfactorily. And partially because I don't think it is actually a necessary or practical pursuit. I mean, even if they do succeed in establishing "biblical kinds", then what? They are going to jump up and declare "See I told you they could fit on the ark!" Not really a huge step forward.

I did comment that regardless of their findings, the results would be rejected - not based on the data, but based on the fact that their research was religiously inspired. I also commented that they feel they have reasons that at least in my feable, little mind are as "empirical" as persuing abiogenesis.

What do you think of that reason? Is it not a good reason to dismiss an idea? Why?

It kinda seems like "If it ain't broke, don't fix it." On one hand it prevents one from following every individual hair-brained scheme and pipe dream that can possily be imagined (and there have been many such foolish notions throughout history - like the spaceship that was in the tail of Haley's Comet and was coming to take the Space Brothers home). On the other hand, we regularly pursue ideas that have no empirical evidence (like abiogenesis and life on other planets). So I suppose you have to weigh the amount effort with the potential value of the results and determine if it's worth pursuing.

As far as Bariminology goes, I too dismiss it as little more than wishful thinking (effort vs. value) and will just let history be the judge. I would think they could find better ways to spend their money. But, anyway, I am satisfied with your answers. At this point, I am more concerned about defining species and speciation.

Thanks


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herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 58 of 450 (540803)
12-29-2009 9:48 AM
Reply to: Message 51 by Dr Jack
12-23-2009 11:32 AM


Speciation
Thanks, Mr Jack.

I wrote a longer post about this in a another thread: The problem of species

I actually had already that post and it did influence my thinking on later posts.


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herebedragons
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Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 59 of 450 (540853)
12-29-2009 2:14 PM
Reply to: Message 57 by RAZD
12-29-2009 1:12 AM


Speciation discussion
Hi Razd

sorry to take so long getting back to you.

No problem at all. I have limited time to spend on this and take the time to think through and research the subject and not just answer off the cuff, so it sometimes takes me a while to reply too. I also think I read somewhere that you are going through chemo? So understandable that it would take a while for you to respond.

In response to my comment on the fossil record, you wrote:

Sorry, but this appears to be wishful thinking, rather than fact.

Not as much wishful thinking as it is my observation at this time. The main reason I joined this forum is to learn about the reasons that scientists accept evolution. I am taking it "step-by-step" and as I learn more about the facts, I am sure I will view many things differently. I am trying to have an open mind, and come to my own conclusions based on what I learn. Because much of our understanding of the fossil record is based on what we know from observation of the present, at this time, I am trying to focus on learning what we actually know from observation of the present.

The only reason we need to classify them is so we can classify them. Organisms don't care what classification they belong to.

This is more the understanding I have in a later post, after reading other threads and some other materials.

Speciation is what is important, not the definition of species.

While I understand what you're saying that speciation happens regardless of how we define "species", the vagueness of the definition is still causing mesome confusion. Here are some examples:

I found examples of Agapornis (Love Birds) that can hybridize across three levels of the polygenetic tree. I realize that the examples happen primarily in captivity, rather than in the wild. But it is still a bit confusing as to why after speciating three times they are still closely related enough to produce viable offspring.

Another example is the greenish warblers. My thinking about this situation goes something like this ... Let's call the original population species 'A'. And each variation around the ring is represented by '1' with the eastern group being '+' and the western group being '-' (to indicate variation is going in different directions). So, the next group to the east would be A(+1) and the next group to the west would be A(-1) and so on until we have, say A(+3) and A(-3), which due to variations in song (language), plumage (physical appearance) and behavior (social factors) they no longer see each other as breeding partners. As you pointed out, there is no place around the ring where it can determined a species 'B' has seperated from the original 'A'. And then there is the questions like what about A(+1) and A(-1) or A(+1) and A(+3) are they seperate species? And so on ...
I liken this to the reason I did not choose a wife that lived in, for example, China. We speak different languages, I may not be attracted to their physical appearance, and they have different cultural and social behaviors. While we are geographically seperated, we have the potential to interbreed - I could hop on a plane, meet someone over the internet or whatever, but I didn't. So, I guess I am not overly impressed with the example of Greenish Warblers as an example of speciation.
What I can appreciate is the potential for the Western Warblers and the Eastern Warblers to evolve in different directions (as they already have to some extent) and develop into distinct species. But where they go from here is unknown as of now. So again it's back to ...

The only reason we need to classify them is so we can classify them. Organisms don't care what classification they belong to.

What I would be interested in learning more about is a mosquito that has developed a variation in it's sexorgans that will not allow it to mate with it's parent population. I couldn't remember what the name of it was nor where I saw reference to it.

In reference to DNA testing of horses / donkeys:

This hasn't been done? Kinda surprising that it hasn't.

Why?

I am curious about that because horses and donkeys have different chromosome numbers and I would be interested as to what the explaination for that is (how did donkeys lose chromosones - or horses gain - not sure which way it happened).

Finally, could you give me a source where I could easily find cladistic and/or polygenetic trees so I could better understand the heritage of organisms? I think it would help me understand the development of chichlids, another common example of speciation, and the horse / donkey / zebra example.

Well, that's all for now. Take care.

Thanks


This message is a reply to:
 Message 57 by RAZD, posted 12-29-2009 1:12 AM RAZD has responded

Replies to this message:
 Message 60 by New Cat's Eye, posted 12-29-2009 2:33 PM herebedragons has not yet responded
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 Message 62 by RAZD, posted 12-29-2009 10:37 PM herebedragons has responded

  
herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 64 of 450 (541798)
01-06-2010 11:46 AM
Reply to: Message 62 by RAZD
12-29-2009 10:37 PM


Re: Speciation discussion
Hi Razd. Sorry to hear about your long battle with cancer. I'msure it has been difficult.

Thanks for link to the Berkley series. It is very well done. I do appreciate how they clearly distinguish between what is theory, what are predictions based on the theory and what is actually observed. This is not always done in evolutionary literature.

What I've learned so far about species and speciation has been pretty unimpressive (and by unimpressive, I mean in an evolutionary sense - there are some truly remarkable things to learn about our world). I am looking for observations that I believe are clues to larger scale changes. I know you will be quick to point out that to see those types of changes we need to look at the fossil record as our time frame for observation is miniscule compared to evolutionary time scale. But what I find appears to be much more like variations within a species.

Take the species Brassica oleracea for example. I was shocked when learned that Kale, Broccoli, Cabbage and a dozen other disgusting vegetables were not just in the same family or even genus, but the same species! Just different cultivars. There is tremendous variation in these plants and the only thing they seem to have in common is they are nasty tasting lol. Is that truly evolution?

And of course, dogs and even horses exhibit drastic amounts of variation within species boundaries. It is duly noted that all above mentioned examples are due to human breeding and cultivation, not natural processes. But also note that human breeding and cultivating is a intelligent, directed process - not undirected and random. Can an undirected, random process create so much diversity? I know, I know ... given enough time it can.

I found this article that was published in PNAS December 22, 2009 (I could not access the actual article as it requires a subscription, but this abstract was posted in several places)

http://www.biologynews.net/..._light_on_horse_evolution.html

quote:
Ancient DNA retrieved from extinct horse species from around the world has challenged one of the textbook examples of evolution ¡V the fossil record of the horse family Equidae over the past 55 million years.

"Overall, the new genetic results suggest that we have under-estimated how much a single species can vary over time and space, and mistakenly assumed more diversity among extinct species of megafauna,"


Their research doesn't discredit the evolution of the horse, but sheds light on the amount of diversity that has occurred within a species over time. Analysis of lineages based on good old fashioned morphology is questionable. We are looking back though millions and millions of years and that has to get a bit fuzzy.

Another example is the reorganization in the metazoan phylogenetic tree.

quote:
DNA sequence analysis dictates new interpretation of phylogenic trees. Taxa that were once thought to represent successive grades of complexity at the base of the metazoan tree are being displaced to much higher positions inside the tree. This leaves no evolutionary "intermediates" and forces us to rethink the genesis of bilaterian complexity.

http://www.pnas.org/content/97/9/4453.full

I won't repeat the details, but the characteristics that were once thought to unite organisms and provide evidence of an evolutionary path, are now being found to be invalid. It is being discovered that it is actually a different set of characteristics that unite the groups.

Another good example of this is the coelacanth. It was once thought that this fish was the predecessor to land animals. It was believed that it used its boney fins to walk along the sea bottom and it had developed a "primitive" lung. With the discovery of living examples of this species, we now know that neither of these assumptions to be true.

quote:
"The modern coelancanth ... has been popularly acclaimed as a "living fossil" and a "missing link" between fishes and tetrapods. This reputation is based on outdated classification and systematic methods, anecdotal evidence and scant regard for intermediate fossil relatives, most of which were described long before Latimeria was discovered... The coelacanth lineage must now be regarded as more distantly related to tetrapods than previously thought... - History of the coelacanth fishes by Peter L. Forey

Even a 1986 encyclopedia (why do I have a set of 20+ year old encyclopedias? My wife got a "deal" on them at a garage sale. Thanks honey ) still held that coelacanths gave rise to land animals and they could "walk" on their fins. What would we believe today if living coelacanths were not discovered? We would be, at the least, looking down the wrong evolutionary path. It is this kind of "dogma" - meaning that once a line of thought becomes ingrained it becomes very difficult to dislodge that line of thinking - that led me to comment on the dog / flea analogy, to which you commented:

I have seen some bad analogies in my time, but this one is rather insulting to scientists.

I certainly didn't mean to insult scientific intelligence or even to insult the scientific process. However, what I do say is that scientists are still human. They are still swayed by the same powers of suggestion, egotism, self-interest and emotions as are all the rest of us. To paint scientists as Mr. Spock types, that deal unemotionally with the "just the facts" would be mistaken. Then take into consideration what then becomes a popular public image, such as coelacanths walking on the ocean floor, or artistic drawings and descriptions of primitive man and other "assumptions" or "speculations" that science regards as only theories or guesses, but can easily become popular images and it can often be difficult to change public or laymen perception.

I do believe scientists are open to the facts and when such facts are presented they adjust their hypothesis or understanding accordingly. (But sometime, public understanding doesn't keep up)

Or they will welcome the new additional data that by and large has verified to an amazing extent the tree of life pattern that has been derived from detailed morpological analysis, with some rearrangements in lineage being inevitable, but the overall pattern still holding.

So when I said they would be "disturbed" at the new DNA results I probably choose the wrong word. I should have said more like "shocked". I also predict that findings based on mitochondrial rRNA will be upset when a new and better test is developed in 10 - 20 years. That's something amazing about science: that whenever one question is "answered" it creates two or more unanswered questions on a never ending quest. That's what keeps scientists going. That's what makes it exciting - no matter how much we think we know, there will always be infinitely more to know than we can even imagine. I guess you could say God is always one or two steps ahead of us .

I think I am going to start looking at the fossil record now. Any suggestions? I have found a couple of really cool sources for fossil pictures, but how can I be sure they are authentic? Particularly the dates are questionable. How can I know dates are reported correctly?

Example: http://www.fossil-museum.com/fossils/

Aside from the fact that they are trying to disprove evolution using the fossils they have on record, are they identified and dated accurately? One thing that caused me concern was they did not use binominal names. They say for example "this is a 30 million year old rabbit" A rabbit? What kind of rabbit? And it's not just this site but most sites with pictures I found. I don't know, so how can I know that fossils are represented accurately?

Thanks


This message is a reply to:
 Message 62 by RAZD, posted 12-29-2009 10:37 PM RAZD has responded

Replies to this message:
 Message 65 by hooah212002, posted 01-06-2010 12:28 PM herebedragons has responded
 Message 66 by RAZD, posted 01-06-2010 10:50 PM herebedragons has responded
 Message 69 by RAZD, posted 01-07-2010 9:30 PM herebedragons has responded
 Message 71 by deerbreh, posted 01-08-2010 4:05 PM herebedragons has not yet responded

  
herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 67 of 450 (542008)
01-07-2010 8:47 AM
Reply to: Message 65 by hooah212002
01-06-2010 12:28 PM


Re: Speciation discussion
Thanks Hooah, but I was looking for suggestions on where I should look and you responded with only an argument of personal incredulity. Also, I was already skeptical of the site because it seemed just too unscientific. Notice I commented that the author did not use scientific names? It really is beautifully illustrated though. So if you want to help, please, please, please give me something I can actually use.

See Message 66 from Razd


This message is a reply to:
 Message 65 by hooah212002, posted 01-06-2010 12:28 PM hooah212002 has acknowledged this reply

  
herebedragons
Member
Posts: 1508
From: Michigan
Joined: 11-22-2009
Member Rating: 10.0


Message 68 of 450 (542011)
01-07-2010 9:03 AM
Reply to: Message 66 by RAZD
01-06-2010 10:50 PM


Re: Speciation discussion
Thanks Razd. For some reason I was not able to find any comments about fossil-museum.com, but I didn't look for "atlas of creation". I was skeptical because it just seemed too unscientific. I expected some dates to be manipulated or some specimens to be misrepresented slightly, but FISHING LURES????

It wasn't so much that it "provided the evidence I wanted" (I wouldn't try to claim that organisms don't change over time - what I am skeptical of is how much they change) but it looked like a very well done project with a very extensive collection. And it would seem anyone that spent that much in producing a work like that would have spent some time doing the research too. But, I guess not. It still makes for some pretty pictures though

Thanks


This message is a reply to:
 Message 66 by RAZD, posted 01-06-2010 10:50 PM RAZD has acknowledged this reply

  
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