April 07, 2007

Evolution's Credibility Problem (part 1)

(Part 1 in a 3 part series)

"The extreme rarity of transitional forms in the fossil record persists as the trade secret of paleontology — we fancy ourselves as the only true students of life’s history, yet to preserve our favoured account of evolution by natural selection we view our data as so bad that we never see the very process we profess to study."
Gould, Stephen J., "Evolution's erratic pace", Natural History, vol. 86, May, 1977

"No wonder paleontologists shied away from evolution for so long. It never seemed to happen. Assiduous collecting up cliff faces yields zigzags, minor oscillations, and the very occasional slight accumulation of change--over millions of years, at a rate too slow to account for all the prodigious change that has occurred in evolutionary history. When we do see the introduction of evolutionary novelty, it usually shows up with a bang, and often with no firm evidence that the fossils did not evolve elsewhere! Evolution cannot forever be going on somewhere else. Yet that's how the fossil record has struck many a forlorn paleontologist looking to learn something about evolution."
Eldredge, Niles, Reinventing Darwin, 1995

"To this day, excuses for the incompleteness of the fossil record, as in the fable of the emperor's clothes, overshadow the inescapable: The expression of novelty in nature arises suddenly."
Schwartz, Jeffrey H., "Adaption and Evolution." (Book Review). History & Philosophy of the Life Sciences, 2001, Vol. 23 Issue 3/4

"Given the fact of evolution, one would expect the fossils to document a gradual steady change from ancestral forms to the descendants. But this is not what the paleontologist finds. Instead, he or she finds gaps in just about every phyletic series."
Mayr, Ernst, What Evolution Is, 2001



Critics of evolutionary theory often point to the inadequacy of the fossil record to support Darwin's claim that life has been one slow progression from a common ancestor to the diverse species we witness today. The above quotes by supporters of evolution, along with many others that could be employed, make it abundantly clear that this criticism is no idle claim. For whatever reason, the fossil record continues to offer a paucity of support for the Darwinian notion of gradual change over time. While it might theoretically still be true, this is not the place to which one must look for a primary defense of the idea.

Apparent transitional fossils — the Holy Grail of evolution — are few and far between, and the geological strata is characterized by sudden appearance of new forms followed by long periods of limited diversity within those forms (i.e., stasis). This leads one to wonder if the transitionals are elusive by nature (as Gould argued) or if they are scarce because there were no such transitions.

If one were committed to the evolutionary hypothesis, and were guided by the fossil evidence alone, then it would seem reasonable to consider the possibility that biological change did not progress in a small stepwise fashion, but instead made great leaps forward ("saltations") at key points in the history of earth. This is the "hopeful monster" scenario advanced by Berkeley geneticist Richard Goldschmidt, which received only ridicule from his peers.

Why, though, should the consideration be so foreign to evolutionary theorists that life has bridged the great functional gaps between species all in single great leaps? Isn't the evidence pointing here, and aren't scientists concerned to follow the evidence wherever it leads? Isn't saltationism even a conceptual possibility? What is the principled objection to such an idea that keeps the theory trained primarily on the gradualistic model?

I submit that it is a matter of credulity.

To accept that the numerous and unique attributes that make up a newly appeared species, genus, family, etc. can come together at once to produce such a novelty is simply beyond the ability for even the most optimistic evolutionist to believe. For example, the bat appears suddenly in the fossil record, essentially in its modern form, complete with echolocation capability, yet no one would presume to suggest that the accompanying bone length and density adjustments, skin arrangement, cardiovascular alterations, and echolocation system all came together in one freak confluence of fortuitous mutations. That is too absurd even to imagine.

Additionally, the theory that the first organism to appear on earth was a single celled creature, like bacteria, has fallen out of favor in modern times. It is now assumed that there must have been some cascading series of "proto-cells" leading up to our ultimate cellular ancestor. And why is this assumed, in spite of the lack of geological or experimental evidence to support the idea? Because now that we have come to grasp the astonishing complexity of the cell it is simply too incredible to believe that it has appeared all at once.

The ironic thing is that critics of evolutionary theory have actually been accused of a "failure of imagination." In explanation of living organisms or their biochemical systems, which are too complex and interdependent to have come about in a stepwise fashion, evolutionists often appeal to imaginative scenarios. Rather than producing fossil intermediates and reproducible chemical pathways, which might settle the question, they offer just-so stories instead. However, an abstract theoretical framework is no substitute for empirical verification, and cannot be considered more than a hypothesis until such verification is forthcoming.

But if incredulity is a valid reproach to an idea, then why can we not also apply it to the supposed smaller steps of the gradualistic theory? Is the theory automatically plausible simply because it is alleged to occur in smaller increments? Are critics so irrational if they fail to be convinced by the evolutionary story even in this form? As it turns out, Intelligent Design (ID) theorists make the point that 1) the "small" steps are not all that trivial and 2) that small steps just won't get you where you need to go in most cases.

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9 Comments:

At 4/07/2007 9:16 AM, Blogger ephphatha said...

Paul, I have always been curious about the claim that there are no transition fossils. Maybe I've got a misunderstanding about what a transition fossil is, but what I think it is, is a fossil from an animal somewhere between animal A and animal B where B is a descendent of A. For example, if horses evolved from rabbits, there should be some animal between horses and rabbits.

Assuming that's right, I don't really see why there's a problem. I mean obviously we aren't going to find fossils for every kind of being that existed. The fossil record is pretty scarce when you think of all the critters that have ever lived on earth.

I look at these gaps in the fossil record kind of like fractional distances between zero and one where zero represents one critter and one represents a critter that evolved from zero. To find a transition fossil, you'd have to find the 1/2 critter. But then you'd still have a gap between zero and 1/2, so you'd have to find the 1/4 critter, and then the 1/8, etc. It seems like you could always argue that there's a missing transition fossil because you can never quite close that gap. How small does the gap have to be before we can say that we do have transition fossils?

I get the feeling sometimes that I've got a big misunderstanding about what a transition fossil is, but this is a question I've had for a long time.

Sam

 
At 4/07/2007 1:17 PM, Blogger Paul said...

No, you are right about transitionals and the theoretical problem of filling in all the gaps. A couple of problems, though. As I understand it, there have not been too many more apparent transitionals found since Darwin's day. If evolution were true, then you'd think the number would constantly creep higher and they'd come to be a dime-a-dozen. As it is, whenever they find a candidate it is hailed with great fanfare (though discredited ones quietly retire). This in itself means that they are a novelty. When's the last time you saw the discovery of a new galaxy make the headlines?

The second problem is that what they do find is that dramatically new creatures just kind of burst into the geological record and stay pretty much the same until the present or they just die out at a point. Now you don't see them, now you do. And quite often this happens in waves, where whole ecosystems just suddenly appear in the record -- the Cambrian Explosion being only the largest example.

Finding related creatures that allegedly evolved into these new ones is more a matter of looking for morphologically similar yet simpler ones in the earlier strata and assuming that these must be the ancestors. It's like saying my furniture evolved and a footstool came first, then dinning chair, then a Lazy-boy, then my sofa. The problem they're having, though, is that the morphological and genetic similarities between such associations often do not coincide, so there are debates over what the ancestor must have been. Again, it's like saying that the stool is said to have preceded the chair because the chair is like it only higher and with a back, yet the stool is found to be made of metal and the chair of wood. What, then, is the most important attribute of a predecessor: wood, or something that looks like a chair?

 
At 4/07/2007 1:29 PM, Blogger ephphatha said...

Now I wish you had read my series on evolution before I deleted it. I discussed morphology a little in there and would like to have gotten your thoughts on it.

 
At 4/07/2007 2:55 PM, Blogger Paul said...

Rats. I just tried this site (http://www.archive.org), which will let you see things as they were in the past, but it only has one earlier date captured on your site. Only two for my site.

However, I also went to Google and searched your site for "Was Darwin Wrong" and it came up with hits to several of the articles. I then selected the "Cached" link and I could read those articles. I read 4, 7, 8, and 10 just now. Very reasonable observations, and pretty "open minded."

 
At 4/07/2007 2:58 PM, Blogger ephphatha said...

Oh the cleverness of you!

 
At 4/07/2007 3:07 PM, Blogger Paul said...

Don't you know? I invented the Internet, so I know all the backdoors. I am the brains behind Al Gore. In fact, I've got his brains (and I'm not giving them back). He's a living example of substance dualism! Your soul can drive your mouth you without even a brain.

 
At 4/07/2007 3:12 PM, Blogger ephphatha said...

Using your method, I was able to recover parts 1-5, part 7, and part 10. There were 12 in all. Once again, you have taught me something new.

 
At 4/09/2007 12:08 PM, Blogger Psiomniac said...

The assumption that evolution predicts more transitional fossils would be found than actually have been, is just false as far as I can tell. Fossilization is a relatively rare event and speciation is predicted to happen in small populations within a geological blink of an eye. Ephphatha is also correct with his almost Zeno like analysis I think.

 
At 4/10/2007 8:15 PM, Blogger Paul said...

Psio,

I'm not evading an answer on this. I think you've raised a point that needs to be adddressed, which relates to Punctuated Equilibrium (if I read you right). I'm just playing around with an answer and trying to decide if it warrants being elevated to a post.

If that's the case, then it comes after part 3 of this series. I've got part 3 done, I'm just measuring my time, especially since I'll be away all weekend.

 

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