One critic of mine (Jeffrey Shallit) took me to task and asked whether I had heard of J. B. S. Haldane's rabbit. I had. Haldane was asked what would falsify Darwinism, and he responded a rabbit fossil in the Precambrian would do quite nicely.

Actually, I doubt that even that would provide decisive disconfirmation of Darwinism since Darwinism seems to have assimilated convergent evolution without so much as a bat of the eye.

But even if we agreed that Haldane's rabbit would provide decisive disconfirmation of Darwinism, it would do much more. Indeed, it would undermine our whole conception of natural history to date.

I see Haldane's rabbit in the same terms as someone asking what would falsify Newtonian mechanics and responding, "Showing that in fact the sun does orbit the earth." Yes, that would do quite nicely, but many independent lines of evidence confirm that this isn't the case, so that, practically speaking, disconfirming Newtonian mechanics is going to require a more subtle test.

Likewise, natural history confirms a certain progression of organisms independently of Darwinism. If we take that natural history as given, what then could disconfirm Darwinism? In the case of Newtonian mechanics, what disconfirmed it was new observations in aspects of the material world that Newton didn't have at his disposal (the very small, as with quantum mechanics, and the very large and fast, as with general relativity).

It seems to me that intelligent design is trying to identify such phenomena in the case of biology -- anomalies, if you will, that Darwin's theory was never meant to handle and which put tremendous pressure on the theory, Michael Behe's irreducibly complex molecular machines being a case in point.

Rather than focus on something so strong as Popper's falsifiability, I want therefore to put the focus on criticizability. Can there be legitimate grounds on which to criticize Darwin's theory? If so, what are they? Are all critics necessarily motivated by a political agenda? Or are there genuine evidential weaknesses with the case for Darwinism?

The problem with testing Darwinism -- which, for Jeff Shallit, means the common descent of all terrestrial organisms -- is the universal domain of the theory. If common descent is the case, as Jeff thinks it is, then the theory necessarily subsumes all known biological phenomena.

Thus one must resort to postulating counterfactual conditionals, such as Precambrian mammals, as potential falsifiers.

I agree that such counterfactuals look pretty slender. But one should press on, and ask, OK, why exactly would the discovery of a Precambrian mammal test common descent? Answer: we know of no natural pathway to mammals directly from the taxa known to exist in the Precambrian (i.e., where that pathway omits the rest of chordate, vertebrate, and tetrapod history). Precambrian mammals, in other words, are a biological impossibility.

Next question: what is the natural pathway, then, to, say, Dickinsonia, an enigmatic Precambrian [Ediacaran] metazoan, from its putative ancestors?

No one knows. Total mystery, in fact, since Dickinsonia was first discovered.

But if the discovery of Precambrian mammals would falsify common descent, because we do not know how they could have evolved early in life's history, then why doesn't the actual existence of Dickinsonia have the same evidential force? We don't know how it evolved either. I developed this example in my talk at Yale in November 2000.

Try playing around with these counterfactual conditionals (e.g., Precambrian mammals, alternate genetic codes, divergent biochemistries), which classically have been given as potential falsifiers of common descent, and you'll find a rich vein for epistemological analysis.

It turns out that even counterfactual conditionals have strong implications for real biology.

P.S. Some biologists argue that universal common descent is logically an untestable, but necessary, axiom of biology. See, for instance, Kenneth Weiss's recent article, "We Hold These Truths to Be Self-Evident," Evolutionary Anthropology 10 (2001): 199-203. Weiss, who is the Evan Pugh Professor of Anthropology and Genetics at Penn State, argues that "evolutionary biology rests more deeply on axioms than we may wish to believe" (p. 199) and "the assumption of a point source [monophyletic origin] is important to the entire theory, so we insist upon spontaneous generation in the beginning, but must forbid it at any other time" (p. 200). Fascinating article. Lewontin, incidentally, holds the same view.

[ 27 February 2002: Message edited by: Paul A. Nelson ]

Methinks we may be violating the following here:

"The start of a thread needs to present some positive insight into complex systems rather than some purely negative criticism."

How about this, from Bill:

It seems to me that intelligent design is trying to identify such phenomena in the case of biology -- anomalies, if you will, that Darwin's theory was never meant to handle and which put tremendous pressure on the theory, Michael Behe's irreducibly complex molecular machines being a case in point.

The question is the evidential significance of certain phenomena. One man's anomaly is another man's unsolved problem. Is common descent sitting on a mountain of anomalies, or a diminishing heap of unsolved problems? If the latter, ID looks much less promising as a research program. If the former, ID is a gold rush waiting to happen.

[ 27 February 2002: Message edited by: Paul A. Nelson ]

quote:

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Originally posted by Paul A. Nelson:
Postive and negative can get murky at the boundary line, Drosera (is thermodynamics strictly negative in proscribing perpetual motion machines -- no, not really), but your worry has merit.

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It's fine with me, I just wouldn't want to have a thread deleted after getting involved with it. Or distract from the interesting experiment here...

quote:

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How about this, from Bill:

It seems to me that intelligent design is trying to identify such phenomena in the case of biology -- anomalies, if you will, that Darwin's theory was never meant to handle and which put tremendous pressure on the theory, Michael Behe's irreducibly complex molecular machines being a case in point.

The question is the evidential significance of certain phenomena. One man's anomaly is another man's unsolved problem. Is common descent sitting on a mountain of anomalies, or a diminishing heap of unsolved problems? If the latter, ID looks much less promising as a research program. If the former, ID is a gold rush waiting to happen.

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I agree, but how do we tell? For example, why can't one argue that Dickinsonia being at least potentially a bilaterally symmetric, segmented "critter", but basically the most primitive one in the fossil record, is a point for evolutionary biology, in that it indicates that (very primitive) bilaterans existed before the Cambrian explosion?

E.g. here is Dickinsonia, all 3.5 inches of it:

...and here is a bunny who is now munching carrots in the big rabbit-hole in the sky:

I think one could credibly argue that one exhibits significantly more complexity (on several measures) than the other...

Drosera

[editted to fix my newbie UBB mistakes...]

[ 27 February 2002: Message edited by: Drosera ]

Typically, the origin of complex biological systems is explained via the Modern Synthesis of Darwinian Natural Selection and Mendelian Genetics. When asked what data might bring this theory into question, a typical response is that finding a rabbit in the precambrian would certainly do the job. This is an appeal to the progression of organisms that occurs in natural history independent of Darwin's theory...

Rather than focus on something so strong as Popper's falsifiability, I want therefore to put the focus on criticizability. In fact, critiques of the Darwin's theory are going to require a more subtle test that doesn't seek to undermine the indpendent line of evidence that natural history has given us and which focuses on data that Darwin himself and most biologists weren't aware of until the very late 20th century.

quote:

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Originally posted by Moderator:
I think Drosera brings up a good point. This thread could be improved by framing it in the following way:

Typically, the origin of complex biological systems is explained via the Modern Synthesis of Darwinian Natural Selection and Mendelian Genetics. When asked what data might bring this theory into question, a typical response is that finding a rabbit in the precambrian would certainly do the job. This is an appeal to the progression of organisms that occurs in natural history independent of Darwin's theory...

Rather than focus on something so strong as Popper's falsifiability, I want therefore to put the focus on criticizability. In fact, critiques of the Darwin's theory are going to require a more subtle test that doesn't seek to undermine the indpendent line of evidence that natural history has given us and which focuses on data that Darwin himself and most biologists weren't aware of until the very late 20th century.

It seems to me that intelligent design is trying to identify such phenomena in the case of biology -- anomalies, if you will, that Darwin's theory was never meant to handle and which put tremendous pressure on the theory, Michael Behe's irreducibly complex molecular machines being a case in point.

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Forgive me, I guess I'm still confused. Are we talking about fossils, or irreducible complexity, or what?

Or perhaps this is a better topic:

What constitute legitimate tests (Popperian or just increased/decreased likelihood) of potential (pre)historical explanations?

...and: What tests do evolutionary theory and ID theory (assuming there is one, someone should define this explicitly) propose? How do these tests follow from the theory?

Doesn't have to be these questions, but we should just pick something rather than talking about everything at once.

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Originally posted by Micah Sparacio:
So the issue here is whether IC systems are sufficient as that subtle test which addresses recently available biological data. Neither Darwin nor the makers of the Modern Synthesis were aware of the functional complexity that exists in the cellular world.

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OK, I'll leave aside precambrian rabbits (wabbit hunting).

(BTW, for the record, I strongly suspect that we *still* aren't really aware of the functional complexity of the "cellular" world. Genomes are great and all, but tracing the path from genome to adult organism is going to be a mind-boggling task. What little developmental biology I know confirms this: e.g., the formation of the blastocoel is really about gap junctions and turgor pressure -- the genes are several levels below this...)

Regarding irreducible complexity (henceforth IC): there is significant confusion about what IC is, and whether it is:

(a) a term that applies to certain structures, and about which an argument is made regarding their evolvability via natural (= 'unintelligent') processes

...or...

(b) something which is *defined* (in part) as something that can't evolve via natural processes.

There is significant ambiguity on this in Behe's original definition and in most other treatments.

So perhaps we could get clarification on this. Is (a) or (b) the correct understanding?

Drosera

[ 27 February 2002: Message edited by: Drosera ]

As is my policy, I will highlight the problems in the hopes that they will be an example to future Brainstorm participants:

1. As Drosera pointed out, this post has been framed as a negative argument, though I do think it can be salvaged as a positive hypothesis based on the superiority of IC (vs. rabbits in the Precambrian) as a method of bringing Darwinian explanations of the origin of complex biological systems into question. I will allow the post to stay opened for this reason.

2. Professional courtesy involves giving your critic the benefit of the doubt and avoiding stereotypes. I consider violations of this nature an attack on character. Attacks on character will typically evoke heated responses. Statements like the following are not acceptable:

"not only do Darwinists not admit that there are any valid criticisms of their theory but that they can't even imagine what such a criticism might look like." -universal stereotype

"Actually, I doubt that even that would provide decisive disconfirmation of Darwinism since Darwinism seems to have assimilated convergent evolution without so much as a bat of the eye." - the word choice here is hostile

"Are all critics necessarily motivated by a political agenda?" - whoever made this claim? This is an example of implying a stereotype.

I have to leave this thread momentarily because of needing to prepare for an upcoming lecture at Andrews University. But I wouldn't agree that Dickinsonia is more primitive than Bugs Bunny without seeing the complexity metric. Furthermore, the issue isn't where Dickinsonia lands on the metric (relative to Bugs), but whether we have a natural pathway to the one critter, where we would lack it for the other (i.e., if Bugs were actually to turn up in the Precambrian).

Be back soon!

P.S. Is Anomalocaris simpler than Bugs? Maybe Drosera could find a picture of Anomalocaris. Some arthropods you don't want to step on accidentally, if you're wading in Paleozoic seas...

[ 27 February 2002: Message edited by: Paul A. Nelson ]

quote:

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Originally posted by Moderator:
1. As Drosera pointed out, this post has been framed as a negative argument, though I do think it can be salvaged as a positive hypothesis based on the superiority of IC (vs. rabbits in the Precambrian) as a method of bringing Darwinian explanations of the origin of complex biological systems into question. I will allow the post to stay opened for this reason.

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I thank Mr. Moderator for his indulgence.

So, before we discuss "IC ... as a method of bringing Darwinian explanations of the origin of complex biological systems into question", we have to know, for once and for all, what it is. It seems to me that there is a fundamental dichotomy in usage that is not fully realized (By Behe or his critics). I described (a) and (b), above.

Let's call (a) the 'structural' definition of IC.
(defined strictly by a set of criteria for what 'systems' should be included)

Let's call (b) the 'probablistic' definition of IC.
(defined, perhaps with elements of (a), but with the additional criterion that those things which can reasonably evolve via natural processes, are excluded from ICness by definition)

What I'm wondering is, which is the 'right' definition? On the 'structural' definition, it is clear that IC structures exist, but whether or not they can evolve via natural processes appears to be a very open question.

On the 'probablistic' definition, only things that "can't" evolve (meaning, in this discussion, that the probability of their evolution via natural processes is vanishingly low; this is practically indistiguishable from "can'" in my opinion) are called IC. This is fine, but then it would appear to be begging the question as to whether or not such systems actually exist in biology.

(the situation in this latter case is almost identical to the circularity argument problem pointed out by Richard A. Johns on this ISCID thread:

http://www.iscid.org/boards/ubb-get_topic&f-10&t-000007

...a problem which, as far as I can tell at least, Dr. Dembski didn.html't really address in his reply)

quote:

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Originally posted by Paul A. Nelson:
Hey, beautiful picture of Dickinsonia!

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The UCMP has a great website...

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I have to leave this thread momentarily because of needing to prepare for an upcoming lecture at Andrews University. But I wouldn't agree that Dickinsonia is more primitive than Bugs Bunny without seeing the complexity metric.

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I suspect that we could do something like "count the number of differently-differentiated segments, divide by the total number of segments" and that would get us there. There is, though, no universally, or even mildly, agreed-upon morphological complexity metric as far as I know...

quote:

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Furthermore, the issue isn't where Dickinsonia lands on the metric (relative to Bugs), but whether we have a natural pathway to the one critter where we would lack it for the other (i.e., if Bugs were actually to turn up in the Precambrian).

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This depends upon what the original argument was for the Precambrian rabbit being a good "falsifier". I don't know that Haldane ever did much more than make his oft-cited exclamation.

quote:

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Be back soon!

P.S. Is Anomalocaris simpler than Bugs? Maybe Drosera could find a picture of Anomalocaris. Some arthropods you don't want to step on accidentally, if you're wading in Paleozoic seas...

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Well, here is Keith Miller's take:

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The Cambrian lobopods occupy a transitional morphological position between several living phyla. The oldest known lobopod from the Early Cambrian is Xenusion. This organism bears similarities to both palaeoscolecid worms and to living onychophorans and tardigrads.26 Furthermore, lobo-pods also have morphological features in common with the arthropods, particularly with peculiar Cambrian forms such as Opabinia and Anomalocaris.27 Recent redescription of Opabinia has also disclosed the presence of lobopod limbs strongly suggesting a lobopod to arthropod transition.28 The discovery of a Cambrian gill-bearing lobopod reinforces this conclusion.29 These forms fall nicely into a transitional position between extant phyla.

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URL: http://www.asa3.org/ASA/topics/evolution/PSCF12-97Miller.html

...which appears to indicate that Anomalocaris makes the Cambrian explosion more understandable in the traditional Darwinian framework, rather than less.

And yes, I expect that Anomalocaris would come out lower on my "segment differentiation" complexity metric.

Plus, we're not talking precambrian anymore...

Drosera

PS: I'll leave the fossil topic for now as it appears that we're heading towards an IC discussion. The most accessible web treatment of "precambrian rabbits" that I know of is Doug Theobald's common descent FAQ at talkorigins:

Prediction 5: Chronological order of intermediates

The *really* important thing is the "positive corellation between phylogeny and stratigraphy, i.e. a positive corellation between the order of taxa in a phylogenetic tree and the geological order in which those taxa first appear and last appear (whether for living or extinct intermediates)". A *negative* correlation (of which a precambrian rabbit would be a data point) would torpedo evolution below the waterline.

Here is the standard phylogenetic tree (BTW, not to scale timewise, only topologically), which is what would be horribly falsified by a precambrian rabbit, but not by things like transitional arthropods in the Cambrian or primitive bilaterans in the precambrian: