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Evolution: Evidence From Transitional Form (Coelacanth)

By john34 in Science
Sat Sep 28, 2002 at 09:22:23 PM EST
Tags: Science (all tags)
Science

Coelacanth (pronounced SEE-luh-canth) is the transition between fish and amphibian. Its colloquial term is 'old four legs' - because, literally, it's a living fossil, and a 'fish with legs'. It is believed that these creatures could, and did, crawl out of the ocean for brief periods of time. Coelacanths were thought to be extinct about 90 million years ago. However, there was a specimen found in 1938! Being a living fossil, it is the sole surviving member of an otherwise extinct taxonomic group (hierarchical classification of organisms that shows natural relationships).


Now, coelacanths are pretty spectacular as they pre-date dinosaurs (the Devonian Period- i.e. `the Age of Fishes,' 360 million years ago) and are still around today, with little to no alterations.

There's a widely accepted scientific belief that life on Earth started in the ocean. There's an interesting story about how two curious scientists tested this belief - Miller/Urey. They set up an experiment to simulate how the Earth may have started to react at the beginning - at first the Earth didn't have any water in it, only hydrogen, oxygen, nitrogen, methane, and ammonia. It was a rocky surface, and was extremely hot - water only existed in the atmosphere as gas molecules. One billion years later it started to cool, and the water condensed - precipitation occurred. Chemical weathering occurred thereafter, and soluble minerals dissolved salts, and began collecting in the lower portions of the rocky bed. Water is so important in any system - the molecules formed after the gases reacted with one another, diffused, and were free to move. These first molecules were DNA and enzymes (must need both) - and co-evolved. Even though silica is most abundant, we are based on carbon! After the experiment, the substance collected was then taken back to a laboratory to be examined (through chromotography) - later it was found that the substance did contain the elements of life - amino acids (which are used to make proteins).

Evolution relates to change (in life), and `to evolve' basically means `to change'. Coelacanths are lobe-finned fish (a group of bony fishes with paired founded fins, suggesting limbs) - it uses these to `perch' on the bottom of the ocean. Coelacanths in an isolated area (an area that didn't affect the rest of the species) may have been subject to random mutations (variation) - environmental factors killed those who did not have the mutations required to survive. Those that had the variation in the population survived and continued to breed (forming a new species) - amphibians (an animal capable of living both on land and in water).

In the 1930s coelacanths were thought to be the direct ancestors of the tetrapods (land-living animals - humans included!) Now though, close relatives called `lungfishes' are believed to have been the direct ancestors. Unlike normal fishes with their swim bladder near the dorsal portion of body cavity, lungfishes have swim bladders that open into the lower side of the foregut. To aquire oxygen, they swim up the surface and swallow air into their swim bladder. Up to 95% of their respiratory oxygen may be acquired in this manner. This means that they do not need to swim to attain oxygen, like normal fish. Their 'lungs' were probably not fully functional at this stage, but an air-gulping mechanism that allowed at least some air breathing. In later species, they could drown if they didn't gulp air.

Coelacanths are heavy-armored fish (a reason for their survival). It is the only living animal to have a fully functional intercranial joint (a division, which separates the ear and brain from the nasal organs and eye - it allows the front part of the head to be lifted when the fish is feeding). Probably the most interesting feature about them would be their `paired fins' which move in a similar fashion to our arms and legs. The original coelacanths were cobalt blue, whereas the more-recent ones are reported to be brownish in colour - caused by pollution.

Coelacanths, unlike most other fish, do not lay eggs. Instead, they give birth to live young (called `pups'). They also have an amphibian-like internal system, which offers further suggestion that amphibians evolved from them. The fish is an opportunist predator (meaning it takes every chance it can to get food). It has an uncanny sense of timing and navigational skills yet to be explained. They are also thought to be long lived, though its exact life-span is still unknown. It has a vertebra (a backbone), and even though they lived primarily in saltwater, the lobe-fins are believed to have evolved in freshwater.

Scientists believed that this species was extinct about 90 million years ago, and it was not until 1938 that a living specimen was discovered by thirty two-year-old, Marjorie Courtenay Latimer. These ancient fishes are vital (and living) evidence to support the theory of evolution, and provide the once `missing' link from fish to amphibians. It is to the utmost importance that we conserve and protect these creatures, for everyone's benefit.

Further Sources:
General - http://www.dinofish.com/
Images - Google's cache
Detailed Description - http://expage.com/page/coelecanth
Everything - Google's search

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Evolution: Evidence From Transitional Form (Coelacanth) | 120 comments (42 topical, 78 editorial, 0 hidden)
+1 SP, for an article on butt-ugly fish. (4.00 / 4) (#2)
by graal on Fri Sep 27, 2002 at 09:14:08 AM EST

And they are butt-ugly. I'd like to see a Coelacanth go mano-a-mano with a Snakefish. Pictures of the Coelacanth and more here

--
For Thou hast commanded, and so it is, that every
inordinate affection should be its own punishment.
-- St. Augustine (Confessions, i)

lol (none / 0) (#3)
by john34 on Fri Sep 27, 2002 at 09:16:19 AM EST

Yes, they are =)

[ Parent ]
Heh. (3.75 / 4) (#9)
by john34 on Fri Sep 27, 2002 at 09:49:44 AM EST

There's only 200-500 of them left in the world. I wouldn't know how they taste =)

(in reply to cooking question) (3.00 / 1) (#10)
by john34 on Fri Sep 27, 2002 at 09:51:07 AM EST

Didn't mean to post as new, but as reply to 'cooking question'. Sorry guys!

[ Parent ]
Only 200-500? (5.00 / 2) (#12)
by Mr Incorrigible on Fri Sep 27, 2002 at 09:53:22 AM EST

They're probably expensive as all bloody hell then. Maybe I'll have the Siberian tiger steak instead tonight.

--
I know I'm a cheeky bastard. My lady tells me so.


[ Parent ]
Why not try the Panda Chops? (nt) (5.00 / 1) (#17)
by graal on Fri Sep 27, 2002 at 10:05:52 AM EST


--
For Thou hast commanded, and so it is, that every
inordinate affection should be its own punishment.
-- St. Augustine (Confessions, i)
[ Parent ]

I try not to buy from Red China. (5.00 / 2) (#20)
by Mr Incorrigible on Fri Sep 27, 2002 at 10:19:16 AM EST

If I bought the panda chops I'd have to import 'em from China -- which means that my money is directly supporting Communism. Now, why the hell would I do that?

--
I know I'm a cheeky bastard. My lady tells me so.


[ Parent ]
Kentukey Fried Panda! (5.00 / 5) (#59)
by zephc on Fri Sep 27, 2002 at 01:04:00 PM EST

It's Finger Ling-Ling Good!

[ Parent ]
Transitional form (4.50 / 2) (#14)
by imrdkl on Fri Sep 27, 2002 at 10:01:01 AM EST

typically implies that the original is improving, in some way. Why is the coelcanth just the same as it has always been?

No need to improve in current env.? (none / 0) (#19)
by lb008d on Fri Sep 27, 2002 at 10:16:34 AM EST


"Kuro5hin: politics and pretension, from the $3,000 leather recliners on the hill overlooking the trenches."DarkZero
[ Parent ]

Be careful there (5.00 / 1) (#35)
by imrdkl on Fri Sep 27, 2002 at 10:56:51 AM EST

An assumption of stasis can lead to other conclusions.

[ Parent ]
Read carefully... Speed kills! (none / 0) (#23)
by john34 on Fri Sep 27, 2002 at 10:27:04 AM EST

Coelacanths in an isolated area (an area that didn't affect the rest of the species) may have been subject to random mutations (variation) - environmental factors killed those who did not have the mutations required to survive. Those that had the variation in the population survived and continued to breed (forming a new species) - amphibians (an animal capable of living both on land and in water).

Basically, the rest weren't affected, and the ones that did have different random mutations simply died. Nothing has caused the ones as they are now to die. That's a good thing =)

[ Parent ]

I dont believe (5.00 / 1) (#26)
by imrdkl on Fri Sep 27, 2002 at 10:33:44 AM EST

that the fossil record bears you out in this. Would not there have been some indicators which delineate the superior mutations in the current species? Or were all the changes in the soft organs?

[ Parent ]
Well... (1.00 / 1) (#33)
by john34 on Fri Sep 27, 2002 at 10:47:02 AM EST

Well, your sig says quite a lot =)

All I can really say if that if they're isolated, they're isolated.

[ Parent ]

reply to your sig (none / 0) (#62)
by zephc on Fri Sep 27, 2002 at 01:07:23 PM EST

"Perl makes Baby Jesus cry!" - me

*joke*

[ Parent ]

DNA preceding RNA? (4.00 / 2) (#48)
by interrupt on Fri Sep 27, 2002 at 12:06:36 PM EST

There is a large body of thought behind the idea that RNA preceded DNA, and that the first simple organisms would have been RNA based. Note that DNA itself is rarely ever functional (other than for encoding information), whereas RNA not only encodes information but also contributes to the structure _and_ function of some cellular components (e.g. ribosomes).

Relevance (5.00 / 1) (#50)
by john34 on Fri Sep 27, 2002 at 12:14:03 PM EST

Its relevance is little in this article, but it is noted. It's theorised, but, I didn't look that far into it.

[ Parent ]
Circular and otherwise suspect reasoning (4.12 / 8) (#56)
by the on Fri Sep 27, 2002 at 01:00:45 PM EST

Everywhere!

Coelacanths are heavy-armored fish (a reason for their survival)
So you're making the claim that a creature survives if it's more heavliy armored. So why aren't all animals heavily armored? Why are there fossils of heavily armored animals no longer in existence today? I suspect you are using circular reasoning: you assume the theory of evolution and then deduce that if a creature is alive today it must be because it has features good for survival. If you are doing this then you mustn't use this species as evidence for evolution.
Coelacanths in an isolated area (an area that didn't affect the rest of the species) may have been subject to random mutations (variation) - environmental factors killed those who did not have the mutations required to survive.
Same goes here.

Which is it: do you want to use evolution to make deductions about coel(e|a)canths or do you want to use them as evidence abouth evolution?

I hope there aren't any creationists reading this.

--
The Definite Article

RE: (none / 0) (#60)
by john34 on Fri Sep 27, 2002 at 01:07:09 PM EST

No, I am not making that claim. I am merely suggesting that is A (one) reason for their survival. It is not the only reason. Other more heavily armored creatures may have had bigger threats that these fish didn't encounter. Eh...

[ Parent ]
Wait a second.. (3.00 / 5) (#68)
by kitten on Fri Sep 27, 2002 at 04:10:31 PM EST

I suspect you are using circular reasoning: you assume the theory of evolution and then deduce that if a creature is alive today it must be because it has features good for survival.

How is this circular reasoning? This is blindingly obvious, even to the Creationist. Animals can and do become extinct, and not merely because of man's actions. Climatic changes, migratory patterns, the reasons are endless. Animals not suited to their environment will die. Nobody denies this.

Therefore, if an animal is alive, it must be because it is well-suited for it's environment.

Creationists don't deny this. They claim that an animal will either live or die according to it's environment and features - but it will not change to adapt.

So you're making the claim that a creature survives if it's more heavliy armored. So why aren't all animals heavily armored?

No, that is not what he is saying. He's saying that for some animals, especially those that are more prey than predator, armor is a good thing, for all the obvious reasons. Armor is good for certain organisms, but not for others - there's a trade-off in weight, speed, agility, and so forth. For some environments, it may be better to have armor as defense; for others, it may be better to be faster or more nimble.

As a side note, there's other animals that predate dinosaurs and are still around today, essentially unchanged; sharks are a good example.

mirrorshades radio - darkwave, synthpop, industrial, futurepop.
[ Parent ]
Unfalsifiable/vacuous (4.00 / 5) (#76)
by the on Fri Sep 27, 2002 at 05:27:11 PM EST

No, that is not what he is saying. He's saying that for some animals, especially those that are more prey than predator, armor is a good thing, for all the obvious reasons. Armor is good for certain organisms, but not for others - there's a trade-off in weight, speed, agility, and so forth. For some environments, it may be better to have armor as defense; for others, it may be better to be faster or more nimble.
These are completely unfalsifiable statements. In order that a statement be falsifiable there needs to be some imaginable state of affairs which contradicts the theory. If we landed on some planet run by wacky invisible aliens who created goofy looking creatures for fun, but you didn't know it, you'd be saying things like "that rabbit like creature has a horn sticking out of its ass because it helps it survive. That dog like creature doesn't because a dog creature is a kind of creature that doesn't benefit from having an ass horn" even though they were designed. You'd still be claiming evolution. This is as bad as a creationist just claiming "God made it that way". Except the Creationist isn't quite as deluded about the nature of their logic.

Going back to:

Coelacanths are heavy-armored fish (a reason for their survival)
The statement in parentheses is completely unverifiable. It's merely tossed out as an article of faith much like a mantra.

--
The Definite Article
[ Parent ]
You're dead wrong, of course. (none / 0) (#113)
by Boronx on Tue Oct 01, 2002 at 02:54:58 PM EST

Even Coelecanths will have some variation in armor. It would be trivial to study them over the course of a dozen generations, and see whether more or less armor improves fitness. The same could be done with a fast fish in the same ecosystem that relies on speed to escape it's predators. In a slightly less convincing study, we could genetically engineer fish with no armor, etc... and see how they do.

These statements are completely falsifiable, and the same experiments would work on your fantasy horn-ass planet. "Hmm, these Rabbits survive fine without their Ass Horn. Is it vestigal? Is it caused by sexual selection?" Well, the fossil record of the rabbit doesn't show any change in horn size, and these amputated rabbits still get laid. There must be some other reason. Let's keep searching."

If you want a get stupid, than maybe your fantasy beings could fool the scientists too. But then maybe it's angels that hold me to the ground and push the planets arround the sun? Or is it the Sun around the planets, i forget.
Subspace
[ Parent ]

Well maybe. But... (none / 0) (#116)
by the on Tue Oct 01, 2002 at 07:24:06 PM EST

Maybe you could direct me to the study which led the original author of the story to say
Coelacanths are heavy-armored fish (a reason for their survival).
If not, maybe you could explain why it was said.

--
The Definite Article
[ Parent ]
I'm intrigued... (none / 0) (#119)
by apteryx on Mon Oct 21, 2002 at 07:33:38 AM EST

Either this is

a) a troll (albeit a rather retiring one), or

b) you're all het up over nothing, or

c) I've missed the boat entirely !

Coelacanths are heavy-armored fish (a reason for their survival).

I take it you're not saying that Ceolacanths aren't heavily armoured fish, so you must object to the statement "a reason for their survival"

It seems to me unreasonable to assume that armour would not contribute to an animals survival, as it has a substantial cost and the animal has survived. I don't see this as supportive of one side or the other in the creationist/evolutionist debate.

If the objection is that this is a tautology, then it isn't (quite) because there are undoubtedly features of the coelacanth that are neutral or damaging to it's chances of survival.Small effects to be sure (they have survived) and at little or no cost to the creature.

And of course the statement is falsifiable.It's perfectly possible to imagine or model a coelacanth without armour, pop it in the same (imaginary or modelled) environment and see how it does.

[ Parent ]

Think bigger (none / 0) (#117)
by djeleveld on Wed Oct 02, 2002 at 08:15:34 AM EST

If we landed on some planet run by wacky invisible aliens who created goofy looking creatures for fun, but you didn't know it, you'd be saying things like "that rabbit like creature has a horn sticking out of its ass because it helps it survive.
You are not thinking big enough about evolution. That horn sticking out of the rabbits ass DOES help it survive. Rabbits without the horn weren't made by the alien race. So the rabbits 'use' the horn and it's effects on the the 'alien race' to proagate. Ok, 'use' is not really the right word but I cant think of anything better. I agree the reasoning is tenous, but so was your example.

Evolution has to do with interactions between and organisim and it's envrionment. Just try and remember that the envrionment is everything that that organisim is likely to interact with. And dont discount things, even the envrionment, as being outside evolutionary processes.

I have to agree that evolution arguments tend to be circular. I'm beginning to think that any argument that describes an organisim's interactions with it's envrionment might have to be circular because the person bringing the argument forward is not free of it's effects.

BTW, I think you reasoning is very sharp. Most people just fall past the step that you noted. At least you applied good reasoning. I just think your view of evolution is limited. Although that's not unusual, almost noone seems to understand the full effects of evolution.

Doug Eleveld

[ Parent ]

ew (3.00 / 2) (#69)
by tps12 on Fri Sep 27, 2002 at 04:11:46 PM EST

creepy

The ocean is a fascinating place, and I have often been entertained looking at and eating its various denizens. But stuff like this freaks me out, no joke. Yuk.

not worded quite right (5.00 / 4) (#79)
by danny on Fri Sep 27, 2002 at 08:15:19 PM EST

Coelacanth is the transition between fish and amphibian.

That's not right (as well as not being particularly grammatical). Living coelecanths are fish, and none of them are the ancestors of any amphibian. The coelecanths are part of a monophyletic taxon (archaic jawed fish) that is a sister group with tetrapods (terrestrial vertebrates).

The sarcopterygians are divisible into two sister-groups, one including the extinct porolepiforms as well as the living coelacanths and lungfish, and the other including the Paleozoic osteolepiformes and the tetrapods.

Robert L. Carroll, Patterns and Processes of Vertebrate Evolution, page 159.

Danny.
[900 book reviews and other stuff]

-1 (2.66 / 6) (#80)
by xriso on Fri Sep 27, 2002 at 08:41:27 PM EST

You should have written about sapphires (sapphires are better than fish (they're shiny and stuff (you know, like diamonds (and they're pretty hard too (you otter look at one sometime))))).
--
*** Quits: xriso:#kuro5hin (Forever)
I didn't know we needed more evidence [nt] (none / 0) (#90)
by dirvish on Sat Sep 28, 2002 at 04:25:39 AM EST



Technical Certification Blog, Anti Spam Blog
spectacular? (4.00 / 1) (#91)
by boxed on Sat Sep 28, 2002 at 08:46:05 AM EST

Now, coelacanths are pretty spectacular as they pre-date dinosaurs (the Devonian Period- i.e. `the Age of Fishes,' 360 million years ago) and are still around today, with little to no alterations
The same goes for most species of sharks, insects, several species of plants and pretty much all bacteria, most notably tha anaerobic species. Oh, and don't forget crocidiles and aligators. This isn't as spectacular as you seem to believe.

Age (none / 0) (#106)
by Richey on Mon Sep 30, 2002 at 02:13:16 PM EST

I don't know about the other species you mention (most species of insects? Hmm), but crocodiles have been around for probably less than 200 million years i.e. around half the age of the coelacanth. Besides it doesn't stop them being spectacular if there are a small number of species of similar age.

[ Parent ]
Pollution changes fish color? (none / 0) (#100)
by treat on Sat Sep 28, 2002 at 07:15:49 PM EST

The original coelacanths were cobalt blue, whereas the more-recent ones are reported to be brownish in colour - caused by pollution.

This is quite a claim. I did a bunch of web searches and I found nowhere that the same claim is made. What is the source of this statement, and where is the evidence to back it up?

RE: (none / 0) (#101)
by john34 on Sat Sep 28, 2002 at 08:08:56 PM EST

Yeah, it does. The colour the water is affects their own colour. This means, if they are in clear, fresh water, they will be cobalt blue, but if they are in 'polluted' water, they are the brownish colour they are now. It's like a chameleon.

[ Parent ]
they live in salt water of the ocean (none / 0) (#110)
by rastafarii on Mon Sep 30, 2002 at 11:15:47 PM EST

i thought they live in salt water well off of the coast in very deep water.

[ Parent ]
pollution? (none / 0) (#112)
by Niha on Tue Oct 01, 2002 at 05:16:07 AM EST

Neither have I understood that of pollution...

[ Parent ]
Similar Result in Sunfish (none / 0) (#120)
by eustatic on Thu Apr 03, 2003 at 04:55:44 PM EST

Having worked as a Field Biologist, I can confirm that Sunfish (Genus Lepomis;"Bream," "Perch") and other freshwater species lose their color in cloudy water.

It's actually a problem in places of great freshwater fish diversity, like Lake Victoria in Eastern Africa. When the water becomes cloudy, (usually as a result of local farming/dumping practices) fish species that rely heavily on visual cues can't tell each other apart, and will attempt to interbreed, to no success.

I'm not sure how this loss of color happens, if the fish makes a decision to conserve energy it would normally use to display color, if it's the result of chemicals in the water, or something else.

I imagine an investigation into this phenomenon in Lepomis would be more productive, as there's a bigger body of work on this genus (Western Temperate Bias and all).

[ Parent ]

My problem... (1.00 / 1) (#102)
by greening on Sun Sep 29, 2002 at 09:23:59 PM EST

...with this article is, if it's a transition from a fish to an amphibian, then how come it still exists? Why didn't they just continue to an amphibian? And if that's natural for evolution (to find a fish to amphibian type creatures (et al)) then, why can you only find the transition from fish to amphibian? Why aren't we finding monkey people and so forth?

It would be much more convincing if people haven't found this fish ALIVE! It is it's own species, not an evolutionary step between fish to amphibian.

I am a creationist but, am also rather open-minded. I've studied both beliefs. I, personally, find evolution (any of it's theories) to be completely redicules and it would be very funny to read about if so many people didn't believe it. While creationism has a few oddities, I find it much more feasible than evolution.

et al, Glenn Murphy
Fair enough (4.00 / 1) (#103)
by adiffer on Mon Sep 30, 2002 at 12:57:56 AM EST

Your question is polite and deserves a response in kind.  Thank you for providing a good example in this area.  We could all learn from your example.

Transitional species are yet another variation on a theme we call life.  The notion that amphibians are derived from this kind of transitional fish does not require the original to be wiped out.  All it requires is enough time and differentiation to cause speciation.  As long as the coelocanth is successful at reproduction through thick and thin times, it should still be around even if its offspring can no longer mate with it.

Where transitional forms tend to suffer is when the follow on species outcompete them in their own niche.  Since the amphibians were likely to occupy a different niche, the transitional fish would be relatively safe if they could defend against other fish.  In human terms, we tend to outcompete the other primates so successfully than many are on the verge of extinction now.  It wouldn't surprise me if we drove our cousins off with a little help from natural forces like disease, climate change, and other predators.  Think about the proposed bridge species between humans and earlier primates and ask how well they would far in modern times.  Add onto this our tendecy to be intolerant of strange looking people and it's not hard to imagine extinction through violence on our family tree.

-Dream Big.
--Grow Up.
[ Parent ]

Alla species are transitions (2.00 / 1) (#104)
by zerblat on Mon Sep 30, 2002 at 03:46:27 AM EST

In some respect, all species are transitions from whatever they evolved from, to whatever will evolve from them. Evolutions happens constantly; spicies aren't static. It's not unlikely that in a few hundred thousand years our descendants will have evolved into a different spicies, assuming we don't bypass evolution completely. But you're right, it's a bit missleading to say "First came fish. Fish evolved into coelacanths and then coelacanths evolved into amphimians".

The point of this is that the anatomy of this species suggests how amphibians evolved from their piscine ancestors.

[ Parent ]

Funny.. (3.00 / 1) (#105)
by AnalogBoy on Mon Sep 30, 2002 at 02:07:17 PM EST

Since evolution has been more">http://www.talkorigins.org/faqs/evolution-fact.html">more or less proven to occur.  I'm sure you meant, as it's now the popular distinction, is "Human Evolution".  The mechanisms are still in debate.  If you try to debate evolution, itself - you're asking to be ignored.  Then there's the matter of theistic evolution.. which is gaining ground, and is a lot more logical than "bang!".

It's also ironic that many people would find the bible funny (okay, or just bad fiction, as you would find the Qu'ran, Siri Guru Granth Sahib,  Bhagavad Gita, or even your closely-related Gnostic gospels) if so many people didn't believe it, and there is substantially less "scientific evidence" (as used in the common language) for Creationism, in any of its theories.

I have a sneaking suspicion you weren't completely open minded, just cynically curious, as many are on both sides of the "battle".   Many people just research the other sides to find ammunition in debates - which is a noble effort.  Unfortunately, following this analogy, you seem to have been sold blanks.

A decent place to start an investigation, if i may suggest, is http://www.religoustolerance.org/.  They try to be as equilateral as possible.

--
Save the environment, plant a Bush back in Texas.
Religous Tolerance (And click a banner while you're there)
[ Parent ]

Really, (1.00 / 1) (#109)
by Estebann on Mon Sep 30, 2002 at 10:19:16 PM EST

I think you can do better than that. Your link that was intended to prove evolution once and for all really only contained a bunch of quotes from people that said that they believed that evolution is a fact.
Then there's the matter of theistic evolution.. which is gaining ground, and is a lot more logical than "bang!".
If you are going to allow some sort of deity into the arguement, you really cannot dismiss any theory based on that deity unless you are claiming to know the nature and motivations of that deity (if in fact that deity is personal (possesing of characeristics like those of a person)).
I'm sure you meant, as it's now the popular distinction, is "Human Evolution".
The problem here is the definition of evolution. If you define it as the author of this story does, 'to change' then no, noone would deny the existence of evolution. If I have a son, he could evovle into a brown-haired person. However, if you define evolution as it is more commonly defined as a change in a creature introduced through a process outside of normal genetic laws. Then you should be less sure of yourself. If you are defining evolution as the change of one creature into a completely different sort of creature then many would be willing to debate you. Creatures (animals, plants, bacteria, etc.) have the capability for a great deal of natural variation through the normal laws of genetics. However, this variation is finite, the organism can only change in ways that are encoded in it's DNA.

This post is probably completely incoherent, but I am tired and coherence takes so much energy.

---
I'll look to like if looking liking move...
[ Parent ]

transitional forms (4.00 / 2) (#107)
by tgibbs on Mon Sep 30, 2002 at 02:46:11 PM EST

...with this article is, if it's a transition from a fish to an amphibian, then how come it still exists? Why didn't they just continue to an amphibian? And if that's natural for evolution (to find a fish to amphibian type creatures (et al)) then, why can you only find the transition from fish to amphibian? Why aren't we finding monkey people and so forth?

This is a bit like asking, "If you came from your parents, why are they still alive?" In evolution, one species is generally not wholly transformed into another. Rather, a few members of one species, separated from the rest by chance, geography, or mutation (a mutation that changes habitat or mating behavior, etc.) begins to diverge, eventually becoming different enough that it no longer mates at all with the "parent" species. The "parent" species may remain, and even give rise to other species, or it may go extinct. At one time, there were clearly multiple "ape man" species running around. What happened to them? There is a distinct possibility that our ancestors killed them off, as they did so many other species.

The coelocanth is not a fish "on its way" to becoming an amphibian--it is a stable modern species, clearly successful in its own niche, that just happens to have preserved more of the characteristics of its parent species than do most modern creatures.

[ Parent ]

Evolution: Evidence From Transitional Form (Coelacanth) | 120 comments (42 topical, 78 editorial, 0 hidden)
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