I just wanted to highlight a comment I posted on Daniel Morgan’s blog since it relates to homology in various organisms.  I was originally going to write my own little blog entry on it, but I figure the comment said most of what I wanted to say anyway, so I’ll just re-post it here.  (You can read the rest of Daniel’s blog to get more context if need be.)

Daniel,

Firstly, thanks for reposting that with the fixed link. For some reason, when I switch between the “preview” and the “posting” screens, it often drops my ending [/a] tag even though I type it in.

As to what you wrote in response, you asked for clarification for my “stepwise” argument. Basically, it’s like this (I’m going to overly simplify for illustration, of course):

Let us suppose that we have a chart between 1 and 10. We have three “fossils” that fit in this chart. Fossil 1 is the oldest (it starts at number 10 on the chart). Fossil 3 is the youngest at number 1. We’ll put an intermediate fossil (Fossil 2) at 5 on the chart.

Now for this example, homologically speaking, Fossil 1 appears to be a predecessor of Fossil 2; and Fossil 2 appears to be a predecessor of Fossil 3. Let us further suppose that we have 7 copies of Fossil 1, 5 copies of Fossil 2, and 12 copies of Fossil 3. Thus, the chart looks like this:

10 ******* [Fossil 1]
09
08
07
06
05 ***** [Fossil 2]
04
03
02
01 ************ [Fossil 3]
—————

* = # of fossils for that step.

The evolutionist looks at this and concludes that this shows a step-wise evolution from Fossil 1 to Fossil 3. However, there is a big gap between step 10 on the chart and step 5. While we have 7 fossils at step 10 and 5 at step 5, we have ZERO between the steps.

Thus, there are no intermediates between Fossil 1 and Fossil 2. Likewise, there are none between Fossil 2 and Fossil 3. Instead, what the fossil record shows is that we have one species (Fossil 1) that is perfectly formed in Step 10. It dies out. Later, in Step 5, a completely new species that looks similar appears; but there are no transitionary fossils between Fossil 1 and Fossil 2. The assumption that they are decendents can only be made by homology and by the dates where they appear (simulated in the example by the Steps of the chart). There is no direct evidence in the fossil record to indicate that Fossil 2 has decended from Fossil 1 though; it can only be assumed.

What I find interesting isn’t so much that there are missing steps in the above, though. What I find interesting is that in the typical fossil record, you’ll find hundreds of fossils at each step and still find none between the steps.

Again, evolution is left only to be assumed by the homologous structures involved.

Since you’re a biochemist, though, I think you can see the problem with the argument from homology :-) On the molecular level, for instance, there are only a certain finite number of ways that a protein can fold. Or to go even more basic, there are only certain elements that can bind together. The elements of life are basically C, O, H, N, and P. Each of these can only combine in a limited number of ways.

Due to the limits of the chemical foundation, all life is going to share some similarities regardless of whether it occurs “naturally” or by design. In other words, as a Creationist (don’t read Y.E.C. in that though), I do not argue that God created special atoms for each creature He created so that humans get human atoms, fish get fish atoms, etc. Instead, He uses the same atoms (and higher atoms are basically just permutations of Hydrogen to begin with).

Anyway (not to ramble too far off topic there), since atoms have a limited number of variations, and since functions necessary for life require specific things to occur at the biochemical level, then it should not be a surprise that the foundations of life are going to be similar. Since these small building blocks are then grouped in a finite manner of groupings (based again on physics and chemistry), there are only a certain number of different structures that could be formed from those smaller building blocks.

Thus, homology on a higher level (e.g. the hand of a man, a bat, and a mole) is ultimately related to homology at a lower level (which I assume you agree with since if it wasn’t true then gradualistic evolution could not explain it either), then this is the sort of thing that one would expect from both a designer using the same building blocks for different organisms and “naturalistic” explanations. In short, homology does not necessitate Darwinism.

But homology is really the only argument to explain the fossil gaps: It appears that Fossil 2 is a descendant of Fossil 1 because they look so similar, so it must have occured due to Darwinism. This, however, isn’t certain.

Add to that the fact that the homology of fossils is based strictly on the physical appearance of the fossils, which isn’t very helpful since two different physical processes could be involved to create the homology. (The reason that two different physical processes can produce similar-looking things is again due to the fact that there are only a finite number of ways that the building blocks can be structured.) Thus, Process 1 could have formed Fossil 1 while Process 2 forms Fossil 2. In such a case, gradualism is inadequate to form a link between Fossil 1 and Fossil 2 unless it can be demonstrated between the two processes, not the physical structure (and the way to tell what these processes would be are, unfortunately, almost always destroyed during the making of the fossil).

In order for gradualism to be demonstrated, it is insufficient to rely on physical homology; one must demonstrate it step by step chemically. But since we can’t get to that level, we instead have people who start with their presuppositions about what should be the case and then interpret the information to ensure that their assumptions come out right.

Anyway, my lunch break is now over so I have to actually go do some work now :-D