PART I: Circumstantial evidence
LiveFreeOrDie posted a good analogy of circumstantial evidence, where, unfortunately - you murdered me. You offered two criticisms to his example: 1) the evidence that was found was recent, where evidence for evolution is often ancient and 2) it relied upon interpretation (your words about this follow):
Yes. He can even be convicted based on circumstantial evidence, even though that is not supposed to happen. And he could even be executed for the crime he did not commit because talented lawyers interpreted and presented the evidence in a convincing manner. And one reason that can happen AND DOES HAPPEN is because nobody was there to witness the event.
If a talented lawyer interprets and prevents the evidence (incorrectly) in a convincing manner, then a person can be wrongfully convicted. However, does this mean that we can never have any certainty about what has happened? Can we not examine the lawyer's interpetations and presentation and search for flaws? If our legal system is working, someone will be there to expose the flaws in his interpretation (not just shout: "It's interpretation!!"). Assuming everyone is doing their job, and the jury is intelligent enough to understand both the interpretations of the evidence and any flaws that are exposed, we should almost never convict an innocent party. If we rule out any evidence that must be interpreted (I suppose because we are assuming that people are too stupid to understand flaws in bad interpretations?) then we can do
no science, and we can leave the majority of criminals on the streets.
Lets look at the "interpretations" of the circumstantial evidence for common descent:
I. Paralogy and homology:
Homology (similarity of structures) helps us to classify organisms into groups. Paralogy (similarity of structures that produce different functions), within those groups, is the first evidence for common descent (of the groups that contain them). It is not conclusive evidence, by itself - it is merely the first. What are the interpretations available?
a - paralogous structures represent the modification of existing structures to meet new environmental needs.
b - paralogous structures represent the design rule that it is simpler to modify existing plans than to design new ones.
c - paralogous structures are a mere coincidence.
d - there are no paralogous structures. The perceived similarities in structure between functionally different organs, tissues, cells, or biochemicals are merely an illusion.
If paralogous structures represent the modification of existing structures to meet new environmental needs, then we can only ever expect to find them where homologous groupings represent a common ancestor to the paralogous forms. If interpretation b is true, then the designer could have used similar structures to perform different functions without regard to concern about homologous groupings of similar structures with similar functions. If c is true, then paralogous structures might be found randomly distributed.
What is found in nature? Well, in nature paralogous structures are found where, and only where, they should be by common descent. Bat wings are structurally similar to mammalian hands (not structurally similar to bird wings).
Whale pelvises are structurally similar to the pelvises of terrestrial mammals (not structurally similar to the ribs of sharks). On the molecular level, the instances of paralogy are overwhelming, always fitting the predictions of common descent. Interpretation a, is therefore, the best fit from a - c. Option d is an equal probability, but if such perceptions are universally illusory, then we cannot trust our senses, and the universe itself might just as well be illusory.
II. Genetic homology. Common descent requires certain biological relationships between organisms that share homologous structures. If common descent is correct, then genetic comparisons should reveal the same relationships discerned by comparisons of body structures. Of course, they do, to a high degree of certainty.
Interpretations:
a - genetic simlarities are, indeed, a result of common descent.
b - genetic similarities are the result of similar design.
c - genetic similarities are pure coincidence.
d - we have already discussed "d".
a, b, & c can be rehashed under the "nested hierarchy" principle from the discussion above. Under that principle, a is again the best fit. Furthermore, a is consistent with other observations from nature. We have only ever observed one source of DNA (genetic material) - that is the reproduction of previously existing DNA.
If I claim that a child, "John Doe" did not develope from the reproduction of existing DNA, but was instead built from scratch in my basement, and my wife argues "no, that is our child", a few tests can be done to help settle the issue. Lets say that a test is dones, and it turns out that John Doe has DNA with 23 human chromosomes, and each gene is identical to one carried by me or my wife. The "interpretations" are the same:
a - the child's DNA came about by reproduction of the DNA of my and my wife's gametes.
b - I designed the child's DNA using my own and my wife's DNA as a model
c - Pure accident
d - ... you know ...
The only one of these explanations consistent with our experience of where DNA comes from is option a.
Furthermore, common descent predicts that even non-functional DNA will have the same kinds of similarities between groups of organisms. We do find that this is the case. The interpretations:
a - common descent explains the similarities between non-functional DNA
b - The designer included these similarities for reasons not related to design/function (such as a joke, or to intentionally mislead us)
c - accident
d - the non-functional DNA has some hidden function that is important to anatomical homology.
e - complete observational incompetence: there are no such similarities.
We can rule out c, leaving a, b, & d unless we are to accept e, with its implicit denial of the possibility of ever having any degree of certainty about anything.
a is the best in this group by occham's razor. For b, one must postulate some reason for the designer to include non-functional DNA in the first place, and some reason for him to create similarities in it that mirrored similarities in body plan. For d, one has to postulate the as-yet undiscovered function of DNA that does not code for proteins, and does not make necessary contributions to structure or regulation... That means we have to find out something that is going on inside the cell that the known functions of DNA does not explain. At this stage in the development of the science of microbiology, that seems like a vanishingly small probability.
III. The Fossil Record:
I am not up to relating the predictions of common descent for the fossil record, for the reason that common descent only makes very generalized statements about what CAN be found in the fossil record, and what CANNOT be found there. Since fossilization is a rare event, no theory can predict exactly what WILL be found in the fossil record. However, I can give a general overview of the evidence from the fossil record and discuss the interpretations in general terms:
1 - Using relative stratigraphic dating techniques, we can determine the relative ages of different fossils.
2 - The oldest fossils are structurally very different from organisms living now.
3 - The development over time of structures and body plans present in organisms now living, but not present in much older fossil organisms, is sometimes recorded in the fossil record. For instance, there are several fossils organisms that incorporate bits of the body plan of modern horses, starting from three-toed dog-like creatures, and progressing through stages to one-hoofed horses (and many other now-extinct horses with somewhat different body plans and structures, by a variety of "routes").
Interpretations:
a - the progression and diversification over time from ancient forms to modern forms is a result of descent with modification, confirming the predictions of common descent.
b - the progression and diversification over time results from a designer who was learning as he went along.
c - the progression and diversification over time was pure coincidence.
d - there was no progression and diversification over time - the fossils are really worm tracks, bear no resemblance to one another or modern forms, and we are too stupid to tell the difference.
e - Most fossils were formed in a great world-wide flood 4000 years ago, and were sorted hydrologically
Discussion:
Common sesnse forces us to throw out c. D has its usual problem. It may be true, but if it is, there is no point in us discussing anything. Humans are just too stupid to understand anything about nature and we might as well not try if D is true. E is falsified. Hydrological sorting would yield a radically different pattern of fossil deposits. That leaves a & b. B requires we postulate a designer smart enough to create life, but who either was not designing toward any particular goal, or could not accomplish that goal on the first try. Occham's razor tells us a.
In order to account for ALL of this circumstantial evidence, then, we must interpret the following:
a - common descent is true
b - common descent is not true. There was a designer who was prone to adapting existing structures for new functions, and restricted himself to doing so in only the ways that can also be accounted for by common descent. He either designed homology into non-functional DNA in ways that can also be accounted for by common descent for some unknown reason, or much of the DNA in our genome has some hidden purpose not even hinted at by microbiological research. He designed living creatures to reproduce, by passing along their DNA, but also created a whole lot of DNA homologously from scratch, over and over again, at various points in history. He either had no final goal for the life he was designing, or could not figure out how to get it right in one step.
c - All of this evidence is the world's most outrageous coincidence.
d - We can never have any kind of scientific knowledge or any degree of certainty about the world we live in, because a whole lot of what we see is illusion.
I'm sticking with A for now, but maybe I will change my mind, when we get to part II, later....
