Tuesday, July 27, 2004

Sisson, Part Three

I will now resume my critique of Edward Sisson's contribution to William Dembski's anthology Uncommon Dissent.

Sisson gives almost no consideration to the evidence in favor of evolution, but he does comment briefly on the fossil record:


But 150 years of investigation into the layers of the earth has not revealed the predicted trnasitional forms. In other words, the “sonar beams” have not found the “land bridge”. Scientists looked beneath the “sea” (the dirt) but the “land bridge” (the transitional forms) was not there. (I now some evolutionists say that the fossil record is sufficient, and every month or so the popular press reports on some obscure fossil discovery that supposedly is evidence of unintelligent evolution. The other contributors to this volume have convincingly refuted that assertion, however - see, for instance, Michael Denton's Evolution: A Theory in Crisis.)


I will explain the references to sonar and land bridges in my next posting.

I'm sure Sisson is aware that virtually every plaoentologist in the world would defend the proposition that the fossil record is entirely consistent with evolutionary expectations. Sisson feels no need to consider their arguments in any serious way, preferring instead to take the word of a single biochemist (Denton). And he's accusing scientists of accepting a low standard of evidence?

Let's take a moment to consider why the fossil record provides such compelling evidence for evolution. A fossil is essentially a snapshot of the fauna that existed in some earlier period in Earth's history. It tells us that an organism having particular characteristics existed at a certain time. Now, if common descent is true, and if the phylogenies inferred from genetic and anatomical considerations are correct, then we can make certain definite predictions about what sorts of animals existed during what time periods.

This is a test evolution passes easily. We can say, for example, that if common descent is true, then the earliest creatures to appear on Earth should also be the simplest. We should find fish appearing before amphibians, which in turn should appear before reptiles. And so on. In other words, the hypothesis of common descent implies that there was a definite order to the appearance of different animals on Earth. The fossil record bears out this prediction. Just one fossil out of place would be enough to cast serious doubt on common descent, but no such fossil has ever been found.

ID offers no explanation for the fossil record. The young-Earther propose that the sequence of fossils represents the differing abilities of animals to avoid the rising flood waters in the time of Noah. I believe that explanation is preposterous, but at least they recognize that there is some phenomenon to be explained.

The second way the fossil record provides evidence for evolution is by providing clear examples of transitional forms. The transitions from reptile to mammal, bear-like mammal to whale, and from australopithcine to human are especially well-documented, as are the fossil histories of horses, rhinos, elephants and many other species.

All of this means nothing to Sisson. We don't even know how he responds to the readily-available facts I just cited, since he doesn't bother to tell us.

He does give us a hint, though, in the following statement:


Science expected to find sequential layers of gradually changing forms, which would confirm the fact of descent with modification (although the fossils, being stone versions of hard body elements auch as bones, would not provide direct proof of the genetic mutation process or that the process was unintelligent and natural). (P. 81)


So it seems that Sisson feels he can dismiss the fossil record as evidence for evolution because it provides few (though not zero) examples of gradual change. Science expected to find such examples, you see. What Sisson omits is that the prediction of “insensibly graded” forms, to use Darwin's phrase, was made at a time when there was no clear understanding of the fossilization process, no good estimate on the age of the Earth, no understanding of the mechanisms of heredity, and no clear theory about the nature of speciation. Once those holes are filled in it becomes clear that Darwin's theories do not imply that series of insensibly graded fossil forms should be found. That was simply a wrong prediction. That is precisely the point Gould and Eldredge were making with their theory of punctuated equilibrium.

Sisson, like all anti-evolutionists, refuses to make the slightest effort to understand PE. He writes:


Advocates of neo-Darwinism, punctuated equilibrium, or of similar theories under other labels, all assert that chance combinations of atoms and molecules, primarily in DNA, given several billion years in which to operate and to be selected, not only can but in fact have given rise to all of the diversity of life we see today.


Of course, punctuated equilibrium is not a theory separate from neo-Darwinism, and it has nothing to do with the mechanisms of evolution. Rather, PE is merely a description of the consequences of Mayr's allopatric model of speciation for the fossil record. As Gould and Eldredge have pointed out (and this aspect of their work is uncontroversial), given the allopatric model we should expect to find periods of relatively abrupt change followed by periods of stasis, just as we do find.

No doubt Sisson would dismiss that as special pleading. He would do that not because the argument is wrong, but because it is easier than actually analyzing the facts of the matter.

Sisson also has some thoughts on the nature of genetic mutations:


Today, the “land bridge” most strenuously advanced as evidence that the generation of new species results from descent with modifications caused by natural, unintelligent, random processes is the mutation of germ cell DNA that supposedly causes beneficial changes in body forms and structures. Technologies sufficient to conduct the investigations into such mutations - the “sonar” that allows this theory to be tested - are fairly recent, but have been around long enough that of the trillions upon trillions of mutations said to have led to all of the genes in all living things, science shold have found proof of a large number of such mutations by now. But it does not appear that even one such beneficial mutation in germ cell DNA that caused a change in body form has been identified. (P.81-82) (Emphasis in original).


Golly! Not one beneficial mutation? Shall we take bets on how many geneticists would agree with Sisson's comment here?

With the exception of neutral mutations, every mutation causes a change in body form. Whether a mutation is beneficial or not will depend partly on the environment in which it occurs, but there are certainly plenty of beneficial mutations that have been documented.

It is possible that what Sisson has in mind is a mutation that causes a large change in the resulting phenotype of the organism. These are not hard to find either, however. It is well known that mutations in Hox genes can cause precisely the large effects Sisson seeks. One especially important example of this phenomenon is described in this short article. The idea that no such large-scale mutations are known is sufficiently absurd, that it effectively eliminates Sisson from deserving serious consideration.

Nonetheless, let's look at what he says next. Picking up where the last quote left off, we find:


The scientific establishment tells us regularly that evidence of beneficial genetic mutation is everywhere, that the development of pesticide resistance by insects, antibiotic resistance of bacteria, or beak-length changes in Galapagos finches caused by drought conditions are all examples of evolution, in which a few individuals develop new features in their DNA to combat a “selection event” that causes a mass die-off. (P. 82)


If this essay were an example of the normal, run-of-the-mill ID stupidity I would assume that Sisson is building up to the standard argument about microevolution vs. macroevolution. Sisson, staying true to form, is building up to something far sillier. We continue:


But all these processes are merely natural variants of breeding, such as that which has been conducted by humans for thousands of years. In every population under study, be it cockroaches under attack by the Orkin Man, bacteria under attack by a doctor, finches suffering because of a drought, or wooly sheep in a breeder's flock, an external event - be it pesticide, medicine, drought, or the preferences of human farmers - causes individuals that have certain traits to die without reproducing, letting others that already have certain other traits reproduce more offspring. Those offspring that also have those traits are in turn able to consume the available food and other necessities of life (whether provided by nature or by the breeders) that otherwise would have been denied to them (either because it was consumed by the offspring of the prematurely deceased indivudals, or was withheld by the breeders). (Emphasis in original) (P. 82)


Now, I know what you're thinking. You're asking yourself “He's not really about to argue that the naturally occurring variation in populations originates in some way other than mutation?” Read on, but first put a soft cushion in front of your keyboard. Your jaw is about to hit the desk. Hard.


What has happened in each instance is that a gene that was present in a smaller proportion of the population before the environmental or breeding condition occurred is now carried by proportionally more (and in total numbers more) offspring than would have been the case had the condition not occurred. Further selective pressures - be they continual application of pesticides, medicine, drought, or breeding preferences - lead to a further focus on those particular traits - traits that were still, however, derived from genes that already existed in the population prior to the first appearance of the condition that caused the selection process to begin. From the perspective of the creatures, whether being bred or naturally selected, the operation of the process is identical. This process is often referred to as “microevolution” althouth there is no actual mutation of any gene at all. (Emphasis in original) (P. 82)


So let me get this straight. He's conceding that large quantities of variation exist in natural populations and he's conceding that sustained selection pressure can cause these changes to accrue to the point where noticeable changes in the population occur. The objection is that we can't be sure that these variations arose via mutation? If anyone reading this believes I have misinterpreted Sisson, please let me know.

Now, I assume that he's using the term 'mutation' as a blanket term to include any well-understood mechanism that causes the offspring's genome to differ from that of its parents. That would include recombinations and duplications, among other mechanisms. Somehow I don't think Sisson is protesting that scientists have misevaluated the relative importance of mutation and recombination in evolution.

Assuming that's correct, is Sisson aware that the gene is the unit of heredity? That it is the genes and the genes alone that get passed on from parent to child? That, ultimately, every aspect of the organism's phenotype is under the control of the genes and that changes in the genes can lead to changes in virtually any aspect of the organism? Where does Sisson believe all this variation comes from if not through changes in genes?

And then there's the style of these two paragraphs. The first begins with the statement, intended to contradict the examples of evolution cited in the previous paragraph, “But all these process are merely natural variants of breeding...”. At the end he explains that from the perspective of the animal there is no difference between natural selection and breeding. He presents this as if this connection is something he discovered; like its something evolutionists have overlooked.

Which is pretty funny when you consider that Darwin devoted the entire first chapter of The Origin to the subject of breeding. He did this for the specific purpose of making his later arguments easier to understand. Of course the continued working of natural selection is analogous to what breeders do. That's the whole freakin' point!

Here's one more bit of Sissonian insanity:


The central problem for the theory of unintelligent evolution is that it asserts that the state of life on earth that existed billions of years ago exhibited very few genes, which the theory must connect with the current state of life, in which there are trillions of genes. The theory implies, but does not ever really try to prove, that the dates the supposed mutations occurred have some timing connection with the dates of population die-offs and the appearance in the fossil record of new body forms. But analysis of the prehistoric dates of die-offs and of population increases in fact tells us nothing about when the genes we see today first came into existence, nor of how they came into existence. The evidence of breeding disproves the assumption that there is any timing link at all between the date a gene (that produces a noticeable new body form) first appears in the gene pool of a species and the date by which creatures that exhibit the body form produced by that gene have become so numerous that science notices the appearance of that new body form in the fossil record. (P. 83)


I give up. If you don't find that paragraph to be obviously stupid, then I doubt any argument of mine will convince you that it is.

And I apologize for quoting Sisson at such length, but I don't want you to think that I am somehow taking his statements out of context.

In this book I was supposed to find the thoughts of intellectuals who find Darwinism unconvincing. Instead I find a group of people who, in Medawar's memorable phrase have been “educated beyond their ability to undertake rational thought”. Perhaps the remaining essays in the book will include at least one paragraph that's not completely idiotic. I'm not holding my breath.