April 18, 2007

Punc Eq: Hide and Seek in the Fossil Record

"Geology assuredly does not reveal any such finely-graduated organic chain; and this, perhaps, is the most obvious and serious objection which can be urged against the theory. The explanation lies, as I believe, in the extreme imperfection of the geological record."
Charles Darwin, Origin of Species.

The prediction of a mounting inventory of transitional fossils was first made by Charles Darwin, who was well aware of the inadequacy of the existing fossil record to prove his theory of evolution. The optimistic task of fleshing out that fossil record was the prime directive for like-minded paleontologists for more than a century afterward. But by the second half of the 20th century it became increasingly clear that the paucity of fossil intermediates was not primarily due to the fragmentary nature of the fossil record (indeed, it was quite adequate in a variety of places); rather, it was reflective of the way that life itself had progressed.

It was after this disappointment of Darwin's largely failed prediction that the theory of Punctuated Equilibrium (courtesy of Stephen J. Gould and Niles Eldridge) was erected. This theory (PE) began with the admission that the fossil record is characterized by long periods of little or no change to species punctuated by the dramatic and sudden emergence of new species. It then added the rationale that the actual work of evolution must typically occur rapidly in isolated population groups, all this being too quick and geographically confined to grant much chance at fossil preservation.

Originally, some were skittish about the theory, because it was the first formal and tacit professional admission that the fossil record had failed to yield the hoped for intermediates, which was seen to lend aid and comfort to creationists. Even though there are notable dissenters to the theory, like Richard Dawkins and Daniel Dennett, it is now largely accepted in some form by supporters of evolution, and is regularly employed as a rebuttal to those filing a grievance against the fossil record.

As a reply, PE is primarily an explanatory device to fill a void, not a description of a proven phenomenon. PE can never be leveraged as evidence for evolution, since claiming PE is merely putting a name to the absence of evidence and adding a companion story. However, that does not stop the theory from being rhetorical genius: "Sure there are few intermediates. Don't be naïve; that's not how evolution works. I should be surprised if you did find them in abundance!" Evolutionists will simply have to bear with those of us who are skeptical of such a reply.

Now, I'm not suggesting there is no story to go behind PE. As I've said, it relates to the supposed accelerated evolution of isolated populations, which are then released into the larger domain where they might have a chance to flourish and be captured in the fossil record. This may have a certain plausibility to it, but, unfortunately, this narrative behind the theory is itself highly problematic.

Let us now look at some of the problems inherent in the "punctuation" scenario.

1) The smaller populations would also mean fewer creatures to yield mutations, beneficial or otherwise. Consequently, you would not expect increased evolutionary opportunities in such isolated groups. Even if the smaller demographics would somehow spread the new genes more quickly, this may be a no better scenario in comparison to the increased odds afforded by a more abundant mainstream population.

2) Evolutionary change begins with fortuitous mutations upon which "natural selection" may act. Isolated populations and environmental pressures do not mean increased rates of mutation, beneficial mutations, or "beneficial" mutations in the direction that would make a difference for a given creature within its given environment (e.g., a mole doesn't need wings and a tree climber doesn't need gills). Evolutionists often speak of the environment and new ecological niches as though they invite certain mutations. This is fallacious language. Need does not cause any random event to occur with a greater frequency or to yield the desired result at any higher rate; it could only cause a fortuitous thing to be preserved if it did happen to occur. For example, my urgent need to get to work on time will not cause the traffic lights to change any faster. And if I need a 4-of-a-kind to win a poker hand it will not increase the odds that I will draw one; but if I happen to be dealt 3 kings you can bet I won't choose any of those for my discard.

3) Even if it is somehow demonstrated that such isolated populations undergo an increased rate of mutation, then this proportionally increases the chances of detrimental mutations, which are vastly more common. And since it is said that mutations are better preserved in limited populations, then this means that there is an increased chance of tainting the entire genetic stock. The same "inbreeding" that is supposed to afford a beneficial mutation the chance to catch hold in the population is perhaps more likely to take down the entire group.

4) On a related note, the inbreeding of smaller populations actually results in genetic erosion, which is just as likely to lead to extinction due to loss of the genetic diversity that permits a species to survive environmental changes. The liability of population bottlenecks such as these has actually been observed and recorded (see here, here, and here for examples).

5) Quite often, the "punctuations" in the fossil record involve a broad spectrum of plants and animals that would not even be related by ecosystem, e.g., air, land, deep water, shallow water, etc. In this case, are we to assume that numerous isolated populations were all busily working in tandem and then were at once released onto the world stage? The biggest single example of this is the Cambrian Explosion, where nearly every phylum (major body plan) suddenly appeared in the fossil record after a long reign of nothing more complex than algae, sponges, and sea cucumbers. And to make matters worse, the Cambrian fauna was primarily warm-loving, but the period immediately preceding it was icy cold, from equator to pole, which doesn't lend much ground for breeding a whole biota of tropical species.

6) The hundreds of millions of years of geological history are often appealed to as grounds for optimism toward what chance can accomplish. But if real evolution can only happen in these periodic, isolated venues, which are interspersed with long spans of stasis, then this dramatically reduces the timeframe in which chance can do its work.

7) Since each of the millions of species would have had to undergo numerous of these "punctuation" surges to reach its present level of complexity, this means that such PE laboratories would need to be occurring at countless times and places. There should then be enough separate sites that we might hope to find at least one such incubator in the geological strata. PE should be, in principle, if not in all likelihood, an empirically verifiable theory if true.

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5 Comments:

At 4/25/2007 6:39 PM, Blogger Psiomniac said...

I know, let's press the 'goddunnit' button eh?

 
At 4/28/2007 10:11 AM, Blogger Paul said...

So, no matter how many failed predictions and statistical problems, we always must assume that evolution is still true and somehow dunnit? It seems that God is never a valid answer because it is cheating, in principle, to intrude a transcendent cause into "science." For this reason, evolution has proved unfalsifiable. It is a philosophical problem more than a scientific one.

 
At 5/01/2007 9:34 AM, Blogger Psiomniac said...

I do not think that evolution is unfalsifiable, rather it has not been falsified so far. I do think that there is a fundamental assymetry to this trawling of so called statistical problems that IDers and creationists present. There are an infinite number of ways to get the model wrong and then show the statistical implausibility of the results. What real evolutionary scientists try to do is much more difficult. That is to try to get the model right, to hone it so that it gets better and can yield verifiable predictions. It is miraculous that they have made the progress that they have in such a relatively short time given the complexity of the task.

 
At 5/02/2007 1:45 PM, Blogger Paul said...

Psio,

The problem is that evolution is not making many successful predictions. It spends most of its time adapting the theory to fit the surprising new data. And there is much data that cannot even be made to fit into the theoretical framework.

For instance, they did not expect that the human genome would consist of only around 25,000 genes (as few as found in corn, and 1/4 of that predicted). And gene studies have upset many classifications of species and proposed evolutionary lineages based on homology (similarity in body design). The physical and genetic similarities often do not line up as they ought.

I also just happened to read the following interesting passages this morning in a book I'm enjoying:

"[C]omparison of [selected gene] sequences from all three domains puts the Eubacteria on one side of the divide, Archaea and Eukarya on the other. . . . We cannot here go into all the ifs and buts; however, it is necessary to note that rooting the tree requires the algorithms to be stretched to their limits, and that an increasing fraction of the trees derived from protein sequences flatly contradicts the conventional wisdom."
Harold, Franklin M., The Way of the Cell, Oxford University Press, 2003, pp. 169-170.

"Could the last common ancestors have been hyperthermophiles? Indeed, should the origin of life be sought, not in Darwin's warm little pond but in some hellish cavern deep beneath the sea? The proposition has been vigorously defended and as fiercely rejected by those who see hyperthermophily as a remarkable adaptation, rather than an ancestral state." (p.172)

Though the author is a supporter of evolution and gives no quarter to Intelligent Design, he does have the integrity to point out the knowledge gaps and contradictory data in the world of molecular biology. Here's another statement from earlier in the book.

"To be sure, the mechanisms that underlie evolution, like those of heredity or energetics, operate at the level of molecules, and some molecular processes that involve random variation and selection among macromolecules mimic biological evolution. But I doubt that evolution by natural selection would have been inferred from molecular science, had Darwin never lived." (p. 6)

It is not so much that evolutionary theory has made miraculous progress; it is simply that we have made great progress in understanding biology, but the advance has left only swirling chaos in its wake. Evolution may be a theory worth entertaining, but until it can generate a better track record of testable and successful predictions, it should remain just that: a theory, not a "proven fact" as so many insist.

 
At 5/03/2007 6:52 PM, Blogger Psiomniac said...

The problem is that evolution is not making many successful predictions. It spends most of its time adapting the theory to fit the surprising new data. And there is much data that cannot even be made to fit into the theoretical framework.

Well I interpret the results differently. I think you overlook many successes that are just taken for granted because they now seem obvious. The subject is immensely complicated. Creationists and IDers love to sieze upon any anomaly. When that is explained they simply move on to the next. It will be ever thus.

 

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