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The Superclass Of Four Limbs


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#1 TempestTossed

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Posted 24 June 2007 - 06:29 PM

The superclass of tetrapods is the topic of this thread. Tetrapoda (Greek four-legged) is a large branch of the family tree that includes you and me, and all amphibians, reptiles, birds and mammals. I will first tell the story of this large family, and the evidence of the family relationship will come at the end.

The "fairytale" story begins 360 million years ago, when there were some fish living in lakes and swamps. They evolved lungs to breathe air when their lake dried up in the summer, so they could remain dormant until the water returned (see lungfish and evistation). Some of them found a better chance of survival by going to another lake instead of going dormant. When they wanted to get to another lake, river, or swamp, they used four leg-like fins to cross the land (see the Tiktaalik, Ichthyostega, and Acanthostega). They still laid their eggs in water, but then the hard-shelled eggs came along, and that gave them the opportunity to lay their eggs on the land, where there were no predators. And why not stay on land? It was lush with delicious untapped vegetation.

Those four-limbed fish split into groups, two of them still alive today: amphibians and reptiles. The reptiles then split into mammals and dinosaurs--and the only descendants of dinosaurs alive today are birds.

So we can divide the living tetrapods into these four main groups:

Amphibians
Reptiles
Mammals
Birds

The theory of evolution predicts that all species within each of those categories will have four limbs at some stage of the organism's lifetime, just as the common ancestors had four limbs.

You may already see a problem. All four of these categories contain animals that do not seem to have all four limbs.

Examples are:

-- caecilians (amphibians)
-- snakes and legless skinks (reptiles)
-- whales and dolphins (mammals)
-- wingless cassowaries (birds)


How do evolutionists explain such a dilemma? The standard explanation is that their ancestors had four limbs, and these species lost them (for the adult stage) because they were better off without them.

But isn't that an ad hoc explanation? It would be... if it were not for the evidence. There are generally five ways of knowing that the ancestors of these species had four limbs.

#1) Stubby embryonic limbs. If an embryo grows a little set of limbs and the growth halts and reverses, then evolutionary biologists see it as an indication that an ancestral species would have kept on growing those limbs. Is there another explanation for the embryonic limbs? Provide it.
#2) Atavistic limbs. Occasionally, an organism belonging to a limbless or two-limbed tetrapod species will be born (perhaps one out of a million) that has four complete limbs! This indicates that the DNA for four limbs still exists in the species of limbless tetrapods.
#3) Vestigial limb remnants. A limbless or two-limbed tetrapod species may leave behind a remnant of its four-limbed ancestors in its anatomy, such as two tiny femurs.
#4) Stubby limbs of closely-related species and less-stubby limbs of less-closely-related species. This indicates an ancestral transition from long limbs to short limbs to no limbs.
#5) Stubby-limbed fossil ancestors. If, by luck, we find and date fossils that anatomically match up with the supposed limbed ancestor of a limbless or two-limbed tetrapod, then no more needs to be said.

So let us examine the list of less-than-four limbed tetrapods. For brevity, I will only provide links, and I will number each of them according to the corresponding explanation from the list above.

THIS IS THE IMPORTANT PART. THE LINKS CONTAIN THE RELEVANT EVIDENCE.

Snakes #1 picture, abstract
Snakes #3
Snakes #5
Legless skinks #4: long legs --> short legs --> no legs
Whales #3
Dolphins #2
Cassowaries #3 (search for "The wing is vestigial" with Ctrl-F and read on)

Instead of ad hoc explanations for less than four limbs among tetrapods, we are given a world of evidence of macroevolution in the form of embryology, atavisms, vestiges, transitional family anatomies, and fossils. Can special creation explain these things? Maybe. I would love to hear it.

I left out caecilians--the limbless amphibians. I don't know anything about them. Would any skeptic of evolution like to make a prediction about what we will find when we study the caecilians?

#2 Springer

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Posted 24 June 2007 - 08:31 PM

Instead of ad hoc explanations for less than four limbs among tetrapods, we are given a world of evidence of macroevolution in the form of embryology, atavisms, vestiges, transitional family anatomies, and fossils.  Can special creation explain these things? Maybe.  I would love to hear it.

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I'm not going to attempt to respond to your post in its entirety, but will tackle for the moment one point. How does embryology provide evidence of macroevolution? Please confine your answer to science.

#3 TempestTossed

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Posted 24 June 2007 - 09:54 PM

I'm not going to attempt to respond to your post in its entirety, but will tackle for the moment one point.  How does embryology provide evidence of macroevolution?  Please confine your answer to science.

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I would be happy to. There is a bunch of information here and perhaps it is best to focus on specifics. I provided two links about snake embryos. One is a picture of a snake embryo with a visible bud that may be a limb. Go to this link and look for the green picture on the right side:

http://individual.ut...ckson/pics.html

The other link is a scientific abstract describing the reduction of limb buds of serpentiform reptile embryos, in case you have doubt about what those lumps are:

http://www.ncbi.nlm....0&dopt=Abstract

"Serpentiform" means snake-like. I confess, I realize now that it may not be a snake--it is only sure to be a limbless reptile like a skink.

ETA: I looked for the complete article online and found it (PDF). The subject of the article is a slow-worm embryo, or Anguis fragilis. There is a Wikipedia article on it with an adult picture here. I am also thinking that the large lump on the picture in the first link I gave you may not be a leg, because the large lump is too far from the head to be a forelimb. I don't know about the smaller lumps. They may be hind limbs or may be something else. The PDF article contains pictures of the limb buds of the slow-worm in figure 1b, not figure 3, which is of the fully-legged European green lizard.

#4 Springer

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Posted 25 June 2007 - 05:10 AM

I would be happy to. There is a bunch of information here and perhaps it is best to focus on specifics. I provided two links about snake embryos.  One is a picture of a snake embryo with a visible bud that may be a limb.  Go to this link and look for the green picture on the right side:

http://individual.ut...ckson/pics.html

The other link is a scientific abstract describing the reduction of limb buds of serpentiform reptile embryos, in case you have doubt about what those lumps are:

http://www.ncbi.nlm....0&dopt=Abstract

"Serpentiform" means snake-like.  I confess, I realize now that it may not be a snake--it is only sure to be a limbless reptile like a skink.

ETA: I looked for the complete article online and found it (PDF).  The subject of the article is a slow-worm embryo, or Anguis fragilis.  There is a Wikipedia article on it with an adult picture here.  I am also thinking that the large lump on the picture in the first link I gave you may not be a leg, because the large lump is too far from the head to be a forelimb.  I don't know about the smaller lumps.  They may be hind limbs or may be something else.  The PDF article contains pictures of the limb buds of the slow-worm in figure 1b, not figure 3, which is of the fully-legged European green lizard.

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So what's your point? Are you saying that and intelligent creator would not have designed snake embryos with visible thickened foci that look like limb buds? How can you draw such a conclusion when neither you nor anyone has the foggiest idea as to how and why an embryo forms in the first place.
All pro-evolution arguments are based one one false assumption... that if a creator existed, he wouldn't have created life the way it is, because you perceive that things look like they evolved. If all the evidence you can give is that something looks like it evolved, that's flimsy evidence indeed. Haeckle's conclusions were based solely on such evidence, and he was dead wrong.

#5 TempestTossed

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Posted 25 June 2007 - 07:24 AM

I'm sorry, I provided the wrong link for the study. Here is the good link for the PDF file:

Developmental mechanism involved in the embryonic reduction of limbs in reptiles.

So the study is this: two reptile embryos are studied. One of the reptiles is a legless snake-like slow-worm. The other is a fully-legged European green lizard. During an early embryo stage, they both have the same buds for limbs, generalizable to all reptiles. For the European green lizard and other legged reptiles, those buds develop into legs. For the slow-worm and other legless reptiles, the development is arrested--it starts but then it stops--and a limbless body is developed.

It actually gets a lot more detailed than that.

The somitic deficiency In embryos of serpentiform species
In all reptiles with well-developed limbs, there are eight somites
(S6 to S13, S1 being the first post-otic somite) that send a ventral
process into the somatopleural area of the future anterior limb. In
the embryos of serpentiform species, the number of somites
sending processes into the territory of the future limb is always less
than eight: 4 (rarely 5) in Anguis fragi/is (Raynaud and Vasse. 1968):
5 in Ophisaurus apodus (Rahmani, 1974): 5 in See/otes brevipes
(Hewitt) (Raynaud et a/., 1974): no somite forms ventral processes
in embryos of snakes (Natrix: Vipera) (Raynaud, 1972a) (Fig. 1, c, d).

It is known. from studies and experiments carried out on
amphibian larvae (Amano, 1960: Finnegan, 1963) and on avian
embryos (Murillo-Ferrol. 1963, 1965; Pinot. 1970: Kieny, 1971)
that the somites play an essential role in the initial development of
the limb. Similar results were obtained in reptilian embryos (Ray-
naud, 1972b. 1977). The reduction in the number of somites
participating in the formation of the limb bud in Anguis fragilis thus
entails a first reduction of the limb anlage. which develops only
opposite the somites forming ventral processes; the limb bud in this
species is thus shortened and lacks a posterior part, that which
develops opposite the other somites (S10 to S13, for instance) in
other tetrapod lizards. The same conclusion is valid for other
serpentiform species (Ophisaurus, See/otes) and similar observa-
tions were made on the anlagen of the posterior limbs.

The reduction in the number of somites participating in the de-
velopment of the limb is accompanied, in Anguis fragilis, by other
deficiencies: early degeneration of many cells in the somitic
processes. segregation of their nucleolar components with a more
or less complete separation of their granular and fibrillar structures.


Details like this normally require an explanation. The theory of evolution provides that explanation. The embryological arrest of limb development removes the limbs of the adult slow-worm and helps it to maneuver through small passages of grass--natural selection. The reason it has limb buds in the first place is because its ancestor had four fully-developed limbs.

But special creation does not explain why this reptile has embryological limb buds, at least not with the same elegance. It is as though the intelligent designer is an engineer who saves a little time in the office by using the same blueprint as a four-legged reptile for a legless slow-worm and telling the contractors to take out the legs mid-construction. I can't completely rule out that possibility. What do you think? What kind of intelligent designer are we talking about?

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Posted 26 June 2007 - 02:44 AM

I'm not reading all that! why cant you admit that the snake lost its legs because of its sin?

#7 ikester7579

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Posted 26 June 2007 - 04:58 AM

I'm not reading all that!  why cant you admit that the snake lost its legs because of its sin?

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2 Corinthians 4:2 But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man's conscience in the sight of God.

3 But if our gospel be hid, it is hid to them that are lost:

4 In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.

#8 TempestTossed

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Posted 26 June 2007 - 08:08 AM

I'm not reading all that!  why cant you admit that the snake lost its legs because of its sin?

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I think that is a great explanation for why snakes have lost their legs. It is right there in the Bible, like a scientific prediction. It is not such a good explanation for why the legless skinks, slow-worms, whales, and dolphins lost their legs. They didn't all tempt Eve with the fruit of the tree. Read the thread. You won't regret it. It is what the evidence for evolution is all about. It isn't about Piltdown Man or Haeckel's embryos.

#9 TempestTossed

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Posted 26 June 2007 - 08:23 AM

2 Corinthians 4:2 But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man's conscience in the sight of God.

3 But if our gospel be hid, it is hid to them that are lost:

4 In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.

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Amen! God bless you, brother! :D

#10 4jacks

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Posted 26 June 2007 - 01:32 PM

From just reading this thread and not the other sources listed, my initial thought is that this is probably another incident of Gill Slits. Even the way you worded it in the thread is very ‘blah’ … it comes across as “Well we don’t know what these little do-hickies are but they look like legs to me!”

Why don’t biologist know what those do-hickies are definitively?

Are all the biologist such PETA activists that they can dissect and embryo and say, “Yup, that’s a leg”

Or maybe they did look into and do know what it is definitively but they didn’t like the results, so they pretend that they didn’t find what they found.

Really there have been too many similar disproven topics, for me to be interested in this one. (the human tailbone, the bones used for s@x in whales, etc.)

Here’s another question.

Why are these little fetus things evolving? If evolution has worked up so wonderfully for all the little animals in the world, how do you believe that all these embryos still go through the same process and cycle through different stages of evolution?

A lot of animals really have to start competing for life as a fetus! If evolution existed the embryo that skipped all the evolutionary processes and went straight to growing into what it is going to be would win!

Besides, They use to say (and they still teach) that humans went through the stages of evolution in the fetus, and that has been pretty well disproven for every stage of development.

So those are the thoughts in my mind, and why I don’t view this topic as evidence of evolution,

Amen! God bless you, brother! :)

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I don’t get it, are you a Christian or an atheist, because that kinda comes across as me saying “Science bless you, Doctor” to you.

#11 TempestTossed

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Posted 26 June 2007 - 05:49 PM

From just reading this thread and not the other sources listed, my initial thought is that this is probably another incident of Gill Slits.  Even the way you worded it in the thread is very ‘blah’ … it comes across as “Well we don’t know what these little do-hickies are but they look like legs to me!”

Why don’t biologist know what those do-hickies are definitively?

Are all the biologist such PETA activists that they can dissect and embryo and say, “Yup, that’s a leg”

Or maybe they did look into and do know what it is definitively but they didn’t like the results, so they pretend that they didn’t find what they found.

I am not a biologist. :) I am like you. I work a $10/hour job at a land surveying business. Don't take what I say about reptile embryos to be representative of what embyologists think. I know only what I find on the Internet. :) Go to the embryologists. Sometimes they publish their studies online, as in this case, and it is way more than just, "well, let me see here, yep, that looks like a leg bud to me." They study many embryos, and they have many reasons for believing that one set of buds are legs, and they know it down to the gene level.

Really there have been too many similar disproven topics, for me to be interested in this one. (the human tailbone, the bones used for s@x in whales, etc.)

I think it is hard to know with justified certainty which ideas are right or wrong unless you pay genuine attention to people like me. You can't just let one side do all the talking. There is a lot more to the human tailbone as it relates to the evidence for evolution than just, "tailbone is useful for sitting, therefore it was intelligently designed" or whatever. I can tell you all about it if you will give me the time--complete atavistic human tails, embryonic human tails, genes for complete human tails, and so on--stuff you didn't know before but brushed aside because you thought the argument was already settled.

Here’s another question.

Why are these little fetus things evolving? If evolution has worked up so wonderfully for all the little animals in the world, how do you believe that all these embryos still go through the same process and cycle through different stages of evolution?

Actually, I don't. That was the biggest scientific mistake of Ernst Haeckel. He was a very respectable and important biologist, but his theory of "embryology recapitulates phylogeny," just isn't so. Because there is no good reason that embryos should reenact its ancestral history or resemble adult stages of life, and they don't. A derived genetic adaptation can happen at any stage, early or late, in an organisms lifetime. A better theory was proposed by Karl Ernst von Baer, whose "Baer's laws" used embryo characters to help construct a family phylogeny, not an ancestral march of progress or whatever. Haeckel's theory is 100 years out of date, so it is a shame that some modern school textbooks still contain vestiges of it, like the inaccurate sketches. I have seen at least one school textbook that advocated the theory explicitly. I think creationists have done a very good thing to expose it.

I don’t get it, are you a Christian or an atheist, because that kinda comes across as me saying “Science bless you, Doctor” to you.

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I am neither a Christian nor an atheist. I was forced to choose 1 of 6 affiliation/religion options in my profile, and "Atheist" is just the closest fit. I actually believe in God, and all the gods. I am an ideatheist--someone who believes that the gods exist primarily as ideas, and very important complex life-like ideas. I am naturalist in my way of looking at everything, and I say, "Amen!" and "God bless you!" because I do as Romans do when in Rome. :)

#12 deadlock

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Posted 26 June 2007 - 07:06 PM

Details like this normally require an explanation.  The theory of evolution provides that explanation.  The embryological arrest of limb development removes the limbs of the adult slow-worm and helps it to maneuver through small passages of grass--natural selection.  The reason it has limb buds in the first place is because its ancestor had four fully-developed limbs. 


Evolution is not equal natural selection , and evolution is not equal mutation.They are different things.Evolution is a theory that says that those two mechanisms can create new species with new body plans.Natural Selection and Mutation exist but they are not capable to create new species with new body plans.So, lost of genetic information by Natural Selection, Mutation or Genetic Drift is perfectly compatible with Creationism.

But special creation does not explain why this reptile has embryological limb buds, at least not with the same elegance.  It is as though the intelligent designer is an engineer who saves a little time in the office by using the same blueprint as a four-legged reptile for a legless slow-worm and telling the contractors to take out the legs mid-construction.  I can't completely rule out that possibility.  What do you think?  What kind of intelligent designer are we talking about?


Things like "Elegance", "I would not do it this way if I was God" are only philosophical arguments.Beyond that, the human being has very little knowledge about embryology and genetics to criticize who made this wonderful work.

#13 TempestTossed

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Posted 26 June 2007 - 07:52 PM

Evolution is not equal natural selection , and evolution is not equal mutation.They are different things.Evolution is a theory that says that those two mechanisms can create new species with new body plans.Natural Selection and Mutation exist but they are not capable to create new species with new body plans.So, lost of genetic information by Natural Selection, Mutation or Genetic Drift is perfectly compatible with Creationism.

Alright! I'm cool if you think maybe the ancestor of the slow-worm was specially created with legs, and then it "microevolved" to lose its legs later on. Is that what you think? I am just making sure.

Things like "Elegance", "I would not do it this way if I was God" are only philosophical arguments.Beyond that, the human being has very little knowledge about embryology and genetics to criticize who made this wonderful work.

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Let me say what I mean by elegant. What we are looking for are the most parsimonious explanations. The elegant explanations are the ones that explain many facts of nature at once. The elegant theories are the ones that can be falsified with different facts than expected, with no need to constantly change the theory to fit every new fact. And the elegant theories predict the facts we find. For example, the theory of evolution predicts that every adult member of the tetrapod branch (amphibians, reptiles, mammals, and birds) will have either four limbs or remnants of its four-limbed past (as in the list of five). An intelligent magical unobservable creator explains things--just not as elegantly. :)

#14 deadlock

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Posted 27 June 2007 - 02:54 AM

Alright! I'm cool if you think maybe the ancestor of the slow-worm was specially created with legs, and then it "microevolved" to lose its legs later on.  Is that what you think?  I am just making sure.


Maybe or Maybe not, I don´t think your evicence is convincing, But it´s compatible with creationism if it had four legs and "devolved " to lose them.

Let me say what I mean by elegant.  What we are looking for are the most parsimonious explanations.  The elegant explanations are the ones that explain many facts of nature at once.  The elegant theories are the ones that can be falsified with different facts than expected, with no need to constantly change the theory to fit every new fact.


So, evolution is not an elegant theory.Almost all evolution´s explanations are Ad hocs created after the fact to fit the data.The fossil don´t match evolution prediction of gradualism then evolutionists created "pontuacted equilibrium", There are animals with homologous traits but don´t have common ancestor the evolutionists created "Convergent Evolution" and so on, the list is long.

And the elegant theories predict the facts we find.  For example, the theory of evolution predicts that every adult member of the tetrapod branch (amphibians, reptiles, mammals, and birds) will have either four limbs or remnants of its four-limbed past (as in the list of five).


No, evolution does not predict that.There is no necessity to any animal to keep remnants of traits of its ancestor.I can show you many traits that we do not share with Chimps even though evolution says we share a common ancestor with them.

An intelligent magical unobservable creator explains things--just not as elegantly.


Macro evolution is unobservable and Magical too.It´s interesting how evolution can make miracles.It created the eye 40 times at least, but it´s a little miracle, there are many others, I´m thinking of writing a book called "The Miracles of Evolution"

#15 TempestTossed

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Posted 27 June 2007 - 07:30 AM

Maybe or Maybe not, I don´t think your evicence is convincing, But it´s compatible with creationism if it had four legs and "devolved " to lose them.

Cool.

So, evolution is not an elegant theory.Almost all evolution´s explanations are Ad hocs created after the fact to fit the data.The fossil don´t match evolution prediction of gradualism then evolutionists created "pontuacted equilibrium", There are animals with homologous traits but don´t have common ancestor the evolutionists created "Convergent Evolution" and so on, the list is long.
No, evolution does not predict that.There is no necessity to any animal to keep remnants of traits  of its ancestor.I can show you many traits that we do not share with Chimps even though evolution says we share a common ancestor with them.
Macro evolution is unobservable and Magical too.It´s interesting how evolution can make miracles.It created the eye 40 times at least, but it´s a little miracle, there are many others, I´m thinking of writing a book called "The Miracles of Evolution"

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OK, at least you know what I mean by "elegant." You think the theory of evolution does not fulfill that standard, and that is fine. :) I don't wish the debate to branch out into five different topics away from the tetrapod superclass. I wish for a good non-ToE explanation for the ubiquity of four limbs in Tetrapoda.

"No, evolution does not predict that.There is no necessity to any animal to keep remnants of traits of its ancestor.I can show you many traits that we do not share with Chimps even though evolution says we share a common ancestor with them."

I am not saying that all related species will be exactly the same. That seems self-evidently wrong. :) There are things that humans will have that chimps will not have. And there are things that chimps will have that humans will not have. Evolution does mean "change." Here is the thing: Whatever humans and chimps share in common, bonobos will also share. And whatever humans and gorillas have in common, chimps and bonobos will share in common as well. That is because of the family tree given by evolutionary theory. If there is a large branch of animals with four legs at its ancestral root, and birds, reptiles, amphibians, and mammals all contain species with four limbs, then it is predicted that every other member of that family will either have four limbs or remnants of its four-limbed past within it. It is an inescapable prediction since the sub-classes of Tetrapoda (birds, reptiles, amphibians, and mammals) retain the four limbs. Evolution would not be able to deal with a mammal that has EIGHT limbs, for example, especially if its close family ties all have four limbs like normal. It is easy to lose limbs through evolution, but it is very hard to get new ones.

#16 4jacks

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Posted 27 June 2007 - 09:58 AM

I am not a biologist. :) I am like you. I work a $10/hour job at a land surveying business.


Well if your looking for a better job, I can get you an interview in Bel Air Maryland. It's a nice place.

He was a very respectable and important biologist,


No he wasn't man, He was a liar and a fraud. Don't call him respectable, call a spade a spade.

  I am neither a Christian nor an atheist.  I was forced to choose 1 of 6 affiliation/religion options in my profile, and "Atheist" is just the closest fit.  I actually believe in God, and all the gods.  I am an ideatheist--someone who believes that the gods exist primarily as ideas, and very important complex life-like ideas.  I am naturalist in my way of looking at everything, and I say, "Amen!" and "God bless you!" because I do as Romans do when in Rome. :)

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Fair enough, never heard of Ideatheist before, Kinda reminds me of that book the Dilbert dude wrote.

#17 deadlock

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Posted 27 June 2007 - 12:03 PM

I am not saying that all related species will be exactly the same. That seems self-evidently wrong.  There are things that humans will have that chimps will not have. And there are things that chimps will have that humans will not have. Evolution does mean "change." Here is the thing: Whatever humans and chimps share in common, bonobos will also share. And whatever humans and gorillas have in common, chimps and bonobos will share in common as well. That is because of the family tree given by evolutionary theory. If there is a large branch of animals with four legs at its ancestral root, and birds, reptiles, amphibians, and mammals all contain species with four limbs, then it is predicted that every other member of that family will either have four limbs or remnants of its four-limbed past within it. It is an inescapable prediction since the sub-classes of Tetrapoda (birds, reptiles, amphibians, and mammals) retain the four limbs. Evolution would not be able to deal with a mammal that has EIGHT limbs, for example, especially if its close family ties all have four limbs like normal. It is easy to lose limbs through evolution, but it is very hard to get new ones.


First, are you saying that all species of birds, reptiles, amphibians and mammals have four limbs or remnants of those?

Second , it´s easy a mutation on a homeobox gene create an extra limb of the same type or lose a limb.That´s an example of micro evolution

#18 TempestTossed

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Posted 27 June 2007 - 04:24 PM

Well if your looking for a better job, I can get you an interview in Bel Air Maryland.  It's a nice place.

OK, what job do you suggest I take?

No he wasn't man, He was a liar and a fraud. Don't call him respectable, call a spade a spade.

It is a mistake to judge any man by their relatively small mistakes, as we so often do with our politicians and celebrities. Ernst Haeckel's scientific career in biology was remarkably huge, and his contributions to evolutionary biology were among the most important. He is the one who coined the term, "ecology," for example. He predicted non-human hominid fossils, and one of his students found the first. He authored hundreds of articles and drew hundreds of sketches. The embryo sketches may have been a lie or an honest sloppy mistake. The shame of his sketches belongs not so much on Haeckel but on modern-day biology textbook publishers who save a little money by using the uncopyrighted and inaccurate embryo sketches.

Fair enough, never heard of Ideatheist before, Kinda reminds me of that book the Dilbert dude wrote.

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It is a word I made up. :)

#19 TempestTossed

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Posted 27 June 2007 - 05:53 PM

First, are you saying that all species of birds, reptiles, amphibians and mammals have four limbs or remnants of those?

Yes, sir. That is what this thread is about.

Second , it´s easy a mutation on a homeobox gene create an extra limb of the same type or lose a limb.That´s an example of micro evolution

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It is not easy for a species, especially the large tetrapods, to gain more limbs than it started with. An individual animal may be born with an extra limb through a mutation, but natural selection always says, "no!" It doesn't last.

#20 deadlock

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Posted 28 June 2007 - 02:42 AM

It is not easy for a species, especially the large tetrapods, to gain more limbs than it started with.  An individual animal may be born with an extra limb through a mutation, but natural selection always says, "no!"  It doesn't last.


So, why did it say "Yes !" four times in the past if it always says "No !" in the present ? Perhaps it has changed its mind ? :P




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