bluefugue

*shrug* Take it up with Dawkins. I simply was responding to your assertion that the hierarchical morphology "isn't and never was" the basis for evolutionary theory (correct me if I have misinterpreted that comment). It may not be the basis (I don't think any one line of evidence is), but it is definitely a basis, and Dawkins isn't the only one who says so. I have read at least one other source that offers the "nested hierarchy" as one of the several lines of evidence for evolution. I forget where -- it was either at Talkorigins or in a report by the National Academy of Sciences (or some similarly named organization).

I don't think anyone could say evolution is the only *possible* explanation for the nested hierarchy. Obviously if you are willing to posit an omnipotent Intelligent Designer, he can design the organisms any way he pleases (this is one reason why ID can never be falsified on evidentiary grounds). But the hierarchy is most certainly adduced as evidence of evolution. That was my only point.

[ February 17, 2002: Message edited by: IesusDomini ]</p>

tronvillain

pangloss:
Of course, it's not really accurate to compare DNA to a blueprint.

Major Billy

Once upon a time, a battleship was docked at a port. Nearby, right at the foot of the pier, was a rowboat. Both were gleaming in the sunlight on one fine day.

"My, how alike we are," said the battleship to the rowboat. "We reflect the sun in very much the same way."

"Hmm," mused the rowboat, "that's true. Yet we have hardly anything else in common. You are an awesome military machine, and I am a humble little pleasure craft."

"We mustn't look at outward differences," protested the battleship.

"Just because we have different functions, it should not obscure our amazing similarities, nor our common evolutionary descent from some metallic ancestor."

"How so?" asked the rowboat.

"Well, let me explain," said the battleship. "We are both made of metal, so we both conduct electricity very well. Our densities must be very much alike. Our melting points are probably quite close.

"I can think of so many other similarities," continued the battleship, "that I am almost tempted to consider myself as little more than a large ocean-going rowboat! Why, I'll bet our respective water displacement is very much the same. There is no doubt that we are both able to float upon water. We are corroded by salt water over long periods of time. We both heat up and cool down very rapidly. We both carry passengers within ourselves at very much the same velocity. Even all of the atoms within us participate in the same type of metallic bonding.

"The list is endless," the battleship concluded, quite pleased with how his argument had turned out. "No rational person can doubt that we had a common evolutionary ancestor at some time in the past."

The rowboat, somewhat embarrassed, replied, "I'm sorry, but I think your good sense has taken flight. Don't you realize that evolution was the cause of racism? I am not a primitive form of battleship, nor are you an advanced kind of rowboat. Stephen Jay Gould has admitted the lack of transitional boats. And evolution was the inspiration for both the Communist and Nazi movements! What about the 4th law of thermos bottles?"

In this fable, the rowboat represents the chimp and the battleship represents the human. Evolutionists commonly cite the extremely close biochemical similarities (as well as similarities between sequences of DNA) of chimps and humans to further the notion that humans are little more than evolved chimps. (See, for instance, UCLA biologist Jared Diamond's book The Third Chimpanzee, which argue--as the book's title claim--that humans are simply another kind of chimpanzee.) Yet the similarities between humans and chimps are at least as consequential as those involving the similarities between battleships and rowboats.

[ February 17, 2002: Message edited by: Major Billy ]</p>

pangloss

No, but in terms of the battleship/fork analogy Woody was trying to make, it was orders of magnitude more accurate.

That is how I was using it - in terms of woody's scenario.

Not reality.

Oolon Colluphid

The most glaringly obvious thing about nested homologies is one bit so often apparently overlooked: that of genetic material. Homologies between, say, vertebrate forelimbs is all very well, but yes, a designer so minded could just be being conservative in his designs. Of course it is more parsimonious to posit common ancestry, given the contortions that a design-promoter would have to go into to defend eg dolphins having to breathe air, but it could still be goddidit.

But with DNA, we’re dealing with the material (or rather, the patterns in it) that we know is passed down generations, sometimes with random changes, even into separating and separated lineages. This is especially relevant for the masses of junk DNA, which, not being used to make its owners’ bodies, has no reason to be similar except if from a common ancestor. The same methods that can be used to show that people of the same family (ie certainly sharing a common ancestor) are related, when applied to populations within species, races, subspecies, sibling species, genera etc etc show them to be related as predicted too. It’s not just homology in the present organisms; since living things had ancestors, DNA patterns contain the history of lineages too. And what they show is relatedness, where creation says none exists.

Oolon

bd-from-kg

IesusDomini:

In reply to my statement:

You said:

But later you said:

But that’s exactly what I was disagreeing with Dawkins about: he did say that it was the only possible explanation. Specifically: “The pattern that you see is a pattern of cousinship; that is the only way to interpret it.” Cousinship by definition entails common ancestry. Common ancestry entails evolution.

Well, I certainly wasn’t saying that no one ever used it as an argument for evolution. I meant that it was never considered (by anything like a consensus of biologists) to be one of the significant reasons for regarding evolution as a well-established theory. I stand by this statement notwithstanding Dawkins’ opinion. It is well-known that Dawkins’ hostility to and contempt for religion is extreme, and it’s pretty obvious (to me at least) that this is warping his judgment here.

For something to be serious evidence for evolution vs. creationism it has to be more compatible with evolution than with creationism. It’s true that, as you say, “... if you are willing to posit an omnipotent Intelligent Designer, he can design the organisms any way he pleases (this is one reason why ID can never be falsified on evidentiary grounds)”. But just because creationism [I prefer this term to ID since ID can mean a lot of things, many of which are compatible with evolution] can be reconciled in principle with any evidence whatsoever, that doesn’t mean that it looks plausible to the typical halfway reasonable person in the face of any evidence whatsoever. The really good evidence for evolution is evidence of the sort that will make the reasonable believer in creationism ask himself “why the heck would God have done things that way? That doesn’t make sense.” The distribution of species in the Galapagos was the first really good evidence of this sort. Origin of Species marshaled a lot of such evidence, which is why it convinced the great majority of reasonable people who took the trouble to become familiar with its arguments. By now, of course, there is so much evidence of this sort that all reasonable people who are familiar with it are convinced, which is why the term “reasonable believer in creationism” looks like an oxymoron nowadays.

lpetrich:

Yes, I have to admit that I overstated the case in saying that evolution was accepted by the “vast majority of serious scientists” before Darwin. It would be more accurate to say that it was accepted by “many” serious scientists. But this actually bolsters my original contention that the mere existence of affinities between species - or even the hierarchical structure, which was actually obvious even in ancient times - was not considered to be significant evidence for evolution by anyone who had not already become convinced of its truth on other grounds.

Yes, this is very good evidence for evolution. It is incomprehensible, on the creationist hypothesis, why God would create, on each island, only species that were very similar to species that could have reached that island from elsewhere.

The pattern formed by the fossil record was already clear enough by 1800 to allow the geological column to be reconstructed with very good accuracy. Of course, the dating was only relative; there was no way yet of determining absolute ages of rocks. But Lyell had shown by 1832 that the earth was very ancient, making it reasonable to think that s there had been enough time for the species found in the fossils to have evolved. On the other hand, it’s true that few “good sequences” of species were known at that point. Thus, whether the fossil record as known at that point constituted “good evidence” for evolution depends on whether you consider the clear evidence of a succession of species over a long period of time to be good evidence for evolution. It appears that you don’t, in which case you must certainly agree with my main point that the mere affinities between species, or even their hierarchical structure, is not good evidence for evolution, since the geological column is much better evidence than that.

After all, my original point was that the "battleship and fork" story is stupid because it completely misrepresents the actual arguments and evidence for evoution.

Coragyps

I've resisted all weekend but I can't stand any more: The whole thesis of the argument leading to this thread is completely forked.

bluefugue

bd:

Honestly, the only reason I quoted Dawkins in the first place was as an example of someone who *did* in fact offer the nested hierarchy as evidence of evolution. Personally I agree with you that it's not the only explanation, but I never claimed to agree with Dawkins. I offered my own opinion as an aside, and my own opinion is perhaps less exclusivist than Dawkins'.

Like I said, I never said I agreed with Dawkins, nor that you should, nor that anyone else should. I simply offered his writing as an example of someone who does suggest the nested hierarchy is evidence of evolution.

Okay, then I think you might have used a different word choice than "isn't and never was." Or perhaps I misread the context. Now that you have clarified it, all is well.

As I said, Dawkins is only one example; I also saw the nested hierarchy adduced (I believe) in a report by the National Academy of Sciences that lays out several lines of evidence for evolution. I don't know how you would define "a consensus of biologists," and I have no desire to start No True Scotsmaning with you. However, I know that at least two sources name it as a major evidence for evolution. Dawkins is one; the report (which was written by a group of scientists, I believe) is another. Talkorigins may be a third. If you really want, I'll go dig up the links, but I doubt either you or I care enough at this point to nitpick about it.

You're probably right. Again, I never said I agreed with Dawkins, nor was my original quoting of him meant as anything other than an example of a (prominent) biologist who adduces the nested (blah blah blah...)

Though, strictly speaking, *everything* is potentially compatible with creationism, since an omnipotent God can do whatever the hell he wants, up to and including sticking fossils in the ground to confuse us. I think you have to factor in Occam's razor and the epistemological biases that underlie science. I.e., common descent may be a simpler & more naturalistic explanation than positing a creator-deity. That doesn't make it right, but in light of how useful science has proved elsewhere, it's reasonable to use the same approach wrt biology.

Yeah, I more or less agree with all this. I don't know whether the nested hierachy is considered a "main leg" of evidence for the theory. I don't know if there is any one main leg. I guess the fossil record might be the main one, but I've heard it said that it is not the most important body of evidence. You take it all together, all the lines of evidence, and it just fits. Like the Galapagos finches you mention: when you add the nested hierarchy to biogeography, each line of evidence is stronger than they were alone. The nested hierarchy has at least the advantage that it is compatible with evolution, and it is explained successfully by evolution (as not all conceivable biological scenarios would be). It is also compatible with ID, though probably in a way that would be less pleasing to Occam.

[ February 18, 2002: Message edited by: IesusDomini ]</p>

HRG

I'd say it is the only possible non-pseudo explanation.
An explanation of X must be a reduction of X to something simpler, more general etc., and it must explain as well why we don't see Y (which is essentially different from X). Thus "A common creator did it" is no more an explanation for the nested hierarchy we see than "my cat created the universe last Thursday, together with stars etc." is no explanation of the energy-production process within a star.

Just my 0.02 Euros.

Regards,
HRG.