Freethought & Rationalism Archive

DNAunion · 11-22-2002, 05:47 PM

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DNAunion: What Behe CORRECTLY states and argues is that an IC biochemical system cannot form by means of a direct, incremental route through simpler functional precursors.

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pz: Unfortunately for him, biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity.

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DNAunion: So Richard Dawkins isn’t a biologist?!?!?

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pz: Yes, he is. And he doesn't argue for what you claim.

DNAunion: Sure he does – he argues that evolution works in direct, incremental routes. Ever hear of his Climbing Mount Improbable analogy? It is a person climbing straight up one hill by taking one small step up at a time. Dawkins doesn’t have people from neighboring mountains jumping over to help. Dawkins doesn’t have the climber leaping from one mountain to another, and then back again or to yet others. Its all uphill – one way, one hill, one climber, small incremental steps, straight path up.

And when Dawkins brags about the “computerized” evolution of a “cupped” eye, complete with a lense, from a simple, flat light-sensisitive cell, there is a direct and continuous series of gradual steps linking the beginning state to the final state. A preexisting lense doesn’t pop off a hand or a tongue to become co-opted by the eye – it arises naturally in the eye itself through a continuous series of small, gradual steps.

And when Dawkins uses his infamous WEASEL program to evolve METHINKSITISLIKEAWEASEL, preexisting words don't jump from the speakers or power supply over to the computer screen to help out. The phrase evolves right before our eyes by cumulative selection involving a direct, incremental series leading from original to final.

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pz: Do you really think he gives ID any creedence at all?

DNAunion: Do you really think I claimed any such thing?

Perhaps you should reread your ridiculous comment and my successful counter - try to understand why are wrong this time, okay.

[ November 22, 2002: Message edited by: DNAunion ]

DNAunion · 11-22-2002, 05:57 PM

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Nic: But even DNAunion's limited claim here -- fatal to the ID movement's reliance on Behe if accepted, BTW, since it means that IC can evolve naturally after all -- turns out not to be true.

DNAunion: I'll hold off debating whether or not my claim is true or not.

First, let me point out that I am not here defending the idea that IC biochemical systems cannot evolve, or that they refute evolution. Nor am I defending Behe's claims overall. I am only sticking up for what I feel is the truth - as I said, if people are going to refute Behe, do so, but do it honestly and with knowledge of which they speak. I am objecting to incorrect counters, such as arguments based on the flawed bases that Behe ignores the possibility of co-option, the Behe claims that an IC system cannot evolve, etc. Sticking up for truth, honesty, and fairness should supercede petty things like party lines.

[ November 22, 2002: Message edited by: DNAunion ]

DNAunion · 11-22-2002, 06:05 PM

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Nic: PZ has nailed the general state of affairs straight-on, but I would point out that even DNAunion's most confident claim ain't true:...

DNAunion: Let's see Nic.

Are you arguing that the Venus Fly Trap's "IC eating system" evolved in a direct, linear way? If so, then according to PZ, you aren't a biologist!

On the other hand, if you are arguing that it evolved by a non-direct route, then you are not countering my claim.

And what part of pz's statements are you claiming are right on? Let me pick one - what about, "biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity"?

[ November 22, 2002: Message edited by: DNAunion ]

pz · 11-22-2002, 07:11 PM

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Originally posted by DNAunion:
Are you arguing that the Venus Fly Trap's "IC eating system" evolved in a direct, linear way? If so, then according to PZ, you aren't a biologist!

On the other hand, if you are arguing that it evolved by a non-direct route, then you are not countering my claim.

And what part of pz's statements are you claiming are right on? Let me pick one - what about, "biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity"?

That is correct.

Biologists do not argue that evolution is linear or direct. You've misread Dawkins if you think he is claiming that his example of "Climbing Mt. Improbable" means that every step taken is up the hill. Populations wander all over the place.

Biologists certainly do not argue for ever-increasing complexity. Parasites, to name one, are an example of a reduction in complexity. And again, the paths taken to achieve a particular state are indirect, so even if one point is more complex than an earlier one, it is not likely that it arrived there by only unrelenting increases in complexity.

You also fail to notice how you've already demolished Behe's argument. You said, "What Behe CORRECTLY states and argues is that an IC biochemical system cannot form by means of a direct, incremental route through simpler functional precursors." This is true. However, evolution does not insist that it can only be generated "by means of a direct, incremental route through simpler functional precursors." It is therefore not an argument against evolution.

I think you might also want to re-read Nic's post. His explanation of how carnivorous plants might have evolved was anything but an assertion that it was direct and linear. Nobody is even trying to counter your claim that the evolution of many structures had to be indirect and non-linear!

Tom Ames · 11-22-2002, 07:18 PM

Yeah, well, but DNAUnion posted FOUR TIMES IN A ROW. That MUST mean he's onto something!

Principia · 11-22-2002, 07:25 PM

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Sticking up for truth, honesty, and fairness should supercede petty things like party lines.

Damn it. He owes me a new irony meter.

Nic Tamzek · 11-23-2002, 10:41 AM

DNAunion,

Let's back up a bit. Biologists, ever since and especially including Darwin, have argued for two major paths to "high-complexity" (traditional definition: lots of parts), high-adaptedness, "really-designed-looking" features of organisms. They are:

1) Specialization of rudimentary function. E.g., the vertebrate camera eye from a light-sensitive spot.

2) Change of function. E.g., fins to feet to hands.

Both are ubiquitous in biological history, both may play a part in the origin of any given complex feature (sometimes more of one than the other). Both are explicitly emphasized by Darwin but also by e.g. Maynard-Smith, Mayr, Gould, Dawkins, and pretty much every biologist worth mentioning. I will produce quotes if you really don't believe me.

As PZ notes, none of these biologists have argued that evolution is always towards increasing complexity, either, because it's not.

Anyhow, returning to Behe: Behe reads Darwin's famous eye quote:

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If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

What Behe thinks this means, and what DNAunion apparently thinks as well, is that Darwin's "numerous, successive, slight modifications" actually means "selection for the same basic function, like in the case of the eye" -- in other words, our case #1, above. Unfortunately, neither Behe nor DNAunion read Darwin closely enough.

Darwin cleverly hid this quote in a section entitled "Modes of Transition". This section follows directly after Darwin's extended discussion of the eye (classic case of specialization of function). Here is the full quote, bolds added:

<a href="http://pages.britishlibrary.net/charles.darwin/texts/origin_6th/origin6th_06.html" target="_blank">http://pages.britishlibrary.net/charles.darwin/texts/origin_6th/origin6th_06.html</a>

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Modes of Transition

If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down. But I can find out no such case. No doubt many organs exist of which we do not know the transitional grades, more especially if we look to much-isolated species, round which, according to the theory, there has been much extinction. Or again, if we take

[page] 147

an organ common to all the members of a class, for in this latter case the organ must have been originally formed at a remote period, since which all the many members of the class have been developed; and in order to discover the early transitional grades through which the organ has passed, we should have to look to very ancient ancestral forms, long since become extinct.

We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind. Numerous cases could be given amongst the lower animals of the same organ performing at the same time wholly distinct functions; thus in the larva of the dragon-fly and in the fish Cobites the alimentary canal respires, digests, and excretes. In the Hydra, the animal may be turned inside out, and the exterior surface will then digest and the stomach respire. In such cases natural selection might specialise, if any advantage were thus gained, the whole or part of an organ, which had previously performed two functions, for one function alone, and thus by insensible steps greatly change its nature. Many plants are known which regularly produce at the same time differently constructed flowers; and if such plants were to produce one kind alone, a great change would be effected with comparative suddenness in the character of the species. It is, however, probable that the two sorts of flowers borne by the same plant were originally differentiated by finely graduated steps, which may still be followed in some few cases.

Again, two distinct organs, or the same organ under two very different forms, may simultaneously perform in the same individual the same function, and this is an extremely important means of transition: to give one instance,—there are fish with gills or brachi� that breathe the air dissolved in the water, at the same time that they breathe free air in their swim bladders, this latter organ being divided by highly vascular partitions and having a ductus pneumaticus for the supply of air. To give another instance from the vegetable kingdom: plants climb by three distinct means, by spirally twining, by clasping a support with their sensitive tendrils, and by the emission of a�rial rootlets; these three means are usually found in distinct groups, but some few species exhibit two of the means, or even all three, combined in the same individual. In all such cases one of the two organs might readily be modified and perfected so as to perform all the work, being aided during the progress of modification by the other organ; and then this other organ might be modified for some other and quite distinct purpose, or be wholly obliterated.

The illustration of the swimbladder in fishes is a good one,

[page] 148

because it shows us clearly the highly important fact that an organ originally constructed for one purpose, namely, flotation, may be converted into one for a widely different purpose, namely, respiration.

[...]

[snip extended discussion of swim bladder-->lung transition, Darwin probably got this backward anyhow, but either way 'tis a change-of-function]

In considering transitions of organs, it is so important to bear in mind the probability of conversion from one function to another, that I will give another instance. Pedunculated cirripedes have two minute folds of skin, called by me the ovigerous frena, which serve, through the means of a sticky secretion, to retain the eggs until they are hatched within the sack. These cirripedes have no branchi�, the whole surface of the body and of the sack, together with the small frena, serving for respiration. The Balanid� or sessile cirripedes, on the other hand, have no ovigerous frena, the eggs lying loose at the bottom of the sack, within the well-enclosed shell; but they have, in the same relative position with the frena, large, much-folded membranes, which freely communicate with the circulatory lacun� of the sack and body, and which have been considered by all naturalists to act as branchi�. Now I think no one will dispute that the ovigerous frena in the one family are strictly homologous with the branchi� of the other family; indeed,

[page] 149

they graduate into each other. Therefore it need not be doubted that the two little folds of skin, which originally served as ovigerous frena, but which, likewise, very slightly aided in the act of respiration, have been gradually converted by natural selection into branchi�, simply through an increase in their size and the obliteration of their adhesive glands. If all pedunculated cirripedes had become extinct, and they have suffered far more extinction than have sessile cirripedes, who would ever have imagined that the branchi� in this latter family had originally existed as organs for preventing the ova from being washed out of the sack?

In fact, Darwin pretty much bashes the reader over the head with the message function is not always constant and you won't understand the evolution of many complex features unless you realize this.

So, to this day, it mystifies me that Behe based his whole argument on assuming that what Darwin thought was that "numerous, successive, slight modifications" meant "a direct pathway where selection acts to favor one function the whole way through".

Eyes turn out to be a good example of a "direct" pathway (= selection for same function), but Darwin emphasizes that this ain't always so, and that functions can change ("indirect" in Behe's parlance).

Briefly, it is also crucial to separate "gradual" from "direct". Gradual changes can be direct or indirect (i.e., keep the same basic function, or change function).

Despite all this, Behe spends about one paragraph on indirect pathways, and asserts (without evidence or even argument) that improbability increases with indirectness, and therefore leaves a gaping hole in the argument upon which the entire ID movement is based.

Now, returning to carnivorous plants: I was making the limited point that even Behe's argument against "direct" (= constant basic function) pathways doesn't work, because of the scaffolding objection. I would say that the pathway for the evolution of Venus Flytraps is "direct" in Beheian sense of basic function (trapping) remaining the same. Of course, it is "indirect" in the common sense of the word, in that all of the change is not in the same direction (first more glue, then less glue).

To emphasize, for Behe:

- "direct" pathway = basic function remains constant

- "indirect" pathway = basic function changes

...for others, the terms might not carry the same meanings.

Gotta go see James Bond now,
nic

(PS to all: I've recommended this page before, I will recommend it again: Darwin texts online...all of 'em:

<a href="http://pages.britishlibrary.net/charles.darwin/texts.htm" target="_blank">http://pages.britishlibrary.net/charles.darwin/texts.htm</a>
)

DNAunion · 11-23-2002, 12:53 PM

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Nic: Let's back up a bit. Biologists, ever since and especially including Darwin, have argued for two major paths to "high-complexity" (traditional definition: lots of parts), high-adaptedness, "really-designed-looking" features of organisms. They are:

1) Specialization of rudimentary function. E.g., the vertebrate camera eye from a light-sensitive spot.

2) Change of function. E.g., fins to feet to hands.

Both are ubiquitous in biological history, both may play a part in the origin of any given complex feature (sometimes more of one than the other). Both are explicitly emphasized by Darwin but also by e.g. Maynard-Smith, Mayr, Gould, Dawkins, and pretty much every biologist worth mentioning. I will produce quotes if you really don't believe me.

DNAunion: No need – you aren’t even addressing the correct position.

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Nic: As PZ notes, none of these biologists have argued that evolution is always towards increasing complexity, either, because it's not.

DNAunion: Unfortunately for both you and especially pz, that is NOT what pz said. Here, please read again his actual statements:

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pz: "biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity"

DNAunion:
(1) NO ALWAYS
In his original statement pz did NOT state anything about ALWAYS. If I can show EVEN ONE EXAMPLE of biologists arguing that evolution of something was or is direct, then I’ve refuted pz.

And, uhm, didn't you TWICE say that the Venus Fly Trap "IC eating system" evolved by a DIRECT route?

(2) OR, not AND
In addition, note that pz joined his criteria with OR, not AND. Thus, they are not a single group that must all be present in the same biological discussion - I don’t even have to show anything about increasing complexity to counter pz: it could stick just to DIRECT (and you yourself have already refuted his claim there!).

So Nic, now that I’ve explained to you what pz actually said, I’ll ask you again.

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DNAunion: [Nic,] Are you arguing that the Venus Fly Trap's "IC eating system" evolved in a direct, linear way? If so, then according to PZ, you aren't a biologist!

On the other hand, if you are arguing that it evolved by a non-direct route, then you are not countering my claim.

And what part of pz's statements are you claiming are right on? Let me pick one - what about, "biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity"?

DNAunion · 11-23-2002, 12:59 PM

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pz: "biologists don't ever argue that evolution is linear, direct, or by ever-increasing complexity"?

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pz: Biologists do not [ever] argue that evolution is linear or direct.

DNAunion: Uhm, ever hear about the increase in beak size of Darwin’s finches? That’s evolution – that was direct. Same "system", same components, same function, same mechanism, just an increase in size due to changes in selective pressures resulting in changes in allelic frequencies in the population.

I guess the people that studied this aren’t biologists either!

[ November 23, 2002: Message edited by: DNAunion ]

pz · 11-23-2002, 01:00 PM

Hmmm. I'm right here. I don't think I need you to translate my words for me, DNAUnion. You're wrong.

You're trying to play rhetorical games, but my meaning is quite straightforward: evolution isn't straightforward. Even in those cases where we seem to see simple trends, inspection at finer levels of detail reveals that the process is by no means linear or direct.

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11-22-2002, 07:18 PM	#25
Tom Ames Regular Member Join Date: Mar 2002 Location: Nacogdoches, Texas Posts: 260	Yeah, well, but DNAUnion posted FOUR TIMES IN A ROW. That MUST mean he's onto something!

11-23-2002, 01:00 PM	#30
pz Veteran Member Join Date: Aug 2001 Location: Morris, MN Posts: 3,341	Hmmm. I'm right here. I don't think I need you to translate my words for me, DNAUnion. You're wrong. You're trying to play rhetorical games, but my meaning is quite straightforward: evolution isn't straightforward. Even in those cases where we seem to see simple trends, inspection at finer levels of detail reveals that the process is by no means linear or direct.

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