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Author Topic:   Where Is Macro-Evolution Occurring
RAZD
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Posts: 19732
From: the other end of the sidewalk
Joined: 03-14-2004
Member Rating: 5.7


Message 106 of 108 (123846)
07-11-2004 11:47 PM
Reply to: Message 99 by Monsieur_Lynx
07-11-2004 2:30 AM


genetic barrier?
and what is the genetic barrier to "macro"evolution? at the level of DNA the changes of "micro"evolution are indistinguishable from those of "macro"evolution.

see http://http://www.evcforum.net/cgi-bin/dm.cgi?action=page&f=5&t=494&p=3


we are limited in our ability to understand
by our ability to understand

RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}


This message is a reply to:
 Message 99 by Monsieur_Lynx, posted 07-11-2004 2:30 AM Monsieur_Lynx has not yet responded

  
gbunty
Inactive Member


Message 107 of 108 (123872)
07-12-2004 2:03 AM
Reply to: Message 99 by Monsieur_Lynx
07-11-2004 2:30 AM


Clarification that fuzzifies
quote:
Perhaps this would help clarify things a bit. Consider the 2 different ways the term evolution is used.
1)We can speak of bacteria evolving immunity to antibiotics. Now, the bacteria are still producing bacteria! This kind of evolution is probably accepted by just about everyone (I seriously doubt you would find a creationist who would dispute this!)
2)According to the theory of universal common descent, bacteria (prokaryotes) evolved into eukaryotes. Here, the word evolution is taken in a different sense.

No, actually, it is not a different sense. In both situations we have a change in a population over generations.

quote:
The distinction is a bit tricky to grasp, but a more formalized way of putting it is that microevolution is a modification of structures that are ALREADY in place. Whereas in macroevolution, new structures appear out of seemingly nothing.

Seemingly nothing is not nothing. New structures are adaptations of existing structures. Often existing structures which were originally used for different purposes.

quote:
For example, when evolutionists speak of fish evolving into amphibians, creatures without lungs, over sufficient time, produce creatures with lungs. This leads to other problems, namely how a transitional form could survive, etc. But anyway that's another topic.

>snip<

Modifying (evolving) the structure of gills won't give us lungs. And no, it doesn't suffice to point out the existence lungfish. Lungfish produce other lungfish and come from other lungfish. There's no rationale for thinking that it or some creature similar to it was a transitional form between ancient fish and modern amphibians.


The problem with all of this is that it is based on the false notion that lungs must have evolved from gills (presumably because they are both "breathing" apparatus).

But historically that is not true. The structures in fish embryos which become gills in the adult fish also exist in mammal embryos. But in mammal embryos they become parts of the ear and throat. So gills did not become lungs in the transition from aquatic to terrestrial life. They became other structures altogether which have nothing to do with breathing.

And yes, let us mention lungfish. For lungfish, like other fish, also have gills and also use them as a breathing apparatus. In short they have a dual system which allows them to take in oxygen from both water and air. So if some sort of ancient lungfish was the ancestor of tetrapods, we have no huge survival problem in the transitional period. All we really need is a modification of fin bones into weight-bearing limbs with digits. And we have some fossil species with precisely those modifications.

This transformation is really no more difficult than the transformations in the horse limb which you already accept as "micro-evolution."

BTW, are you aware that just as mammals have a homologue to gills in their ear/throat area, fish have a homologue to lungs. It is called a swim bladder and is used to regulate gases and to position the fish vertically in the water column. According to Stephen J. Gould, it is probable that the swim bladder is a modified lung inherited from ancestral lungfish.


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Silent H
Member (Idle past 3866 days)
Posts: 7405
From: satellite of love
Joined: 12-11-2002


Message 108 of 108 (123896)
07-12-2004 7:36 AM
Reply to: Message 105 by crashfrog
07-11-2004 11:03 PM


Maybe that was my point - it's fairly stupid to talk about "fundamental differences" when we don't even know what the fundamentals are.

Agree completely. Of course we all know what the fundamentalists are.

if I cut and pasted the base sequence for antibiotic resistance and the sequence for eukaryotic membranes, there'd be no way you could tell which was which.

Also agreed, though I was trying to suggest that evidence is beginning to build that the latter (creation of eukaryotic life) was not due to simple gene sequence alteration. It may have happened that way, but symbiosis theorists are racking up some good evidence it was not that simple. It is more about the loss of (or turning off of) gene sequences within more than one species, where the two are cohabitating (one within another) that "created" a more complex singular organism.


holmes
"...what a fool believes he sees, no wise man has the power to reason away.."(D. Bros)
This message is a reply to:
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