From: bivalve (bivalve@mail.davidson.alumlink.com)
Date: Tue Feb 11 2003 - 20:24:01 EST
>Are you saying that someone has shown that the specific mutations that caused the species changes were indeed random, in any sense?<
It is relatively trivial to show that the mutations are random in the colloquial sense of humanly unpredictable. There is no known scientific reason why one organism has a particular mutation and another does not. We cannot examine the fossils of one age and thereby predict with certainty what kinds will be successful at some later time. Evolution is no less (nor more) random in this way than is human history or the weather.
The observed occurrence of mutations appear to be best described by a probabilistic model, as is the pattern of genetic drift (whereby a mutation, once it occurs, either spreads through a population or disappears from it). These models must also take into account the directional influences of selection and other influences, but it does suggest a mathematically random component to evolution. Studies such as the one I mentioned by Dan Miller show that some patterns resulting from evolution also are described well by a probabilistic model.
Evolution itself, not having goals of its own, could be described as metaphysically random; however, given the confusion over the issue it is important to assert that God is sovereign over the process but that the process of evolution itself cannot be equated with progress.
>To me "random" means what I think it means in most of science, namely, that a sufficient number of samples will fit a probability distribution function...<
I agree, but the other senses that I mentioned are often confused with this.
>My point is that no one needs to believe that such random mutations are the ones that led to emergence of new species, because no one can prove, for example, that God did not skew the distributions for his own purposes when new species emerged. I do in fact believe that some "descent with modification" occurs from random mutations, but this is just a belief, and I'd have no reason to dispute anyone who did not believe it. I cannot believe that ALL descent with modification comes from random mutations.<
New species emerge all the time. There is no physical evidence that the occurrence of the mutations involved (if any) cannot be mathematically described by a probabilistic function.
>Actually, your later comment, ".if God is sovereign over the outcome of casting lots, as various passages attest, then this sort of randomness does not exclude God," says precisely, in different words, that God indeed may skew the distributions. So I guess in this respect we're in agreement. It's just that I would say you lose randomness as soon as there is any deliberate skewing. Is this just semantics? I don't think so. <
I think we are addressing different perspectives. Is there any way to measure the occurence of important mutations that would detect a deviation from the probabilistic model? Not that I can think of; as far as we can tell from science, there is a given probability for any particular mutation to occur. On the other hand, theologically I think that every mutation is determined by God. Obviously, it is not possible to measure the mutation rates in the past to test the statistical pattern, but I do not think it was necessary to have a statistical anomaly for God to bring about a particular mutation. For example, He is certainly capable of designing the universe so that a cosmic ray is produced at exactly the right place and time to cause a particular mutation when it reaches Earth. Thus, random appears to me to be a good scientific descriptor of certain aspects of evolution but a poor theological descriptor of evolution at an ultimate level.
>The accepted mechanism of organic evolution in particular has never been put to the test, so it has garnered much more respect than it deserves. A proper test to give it true respectability would show that mutations known to be random in the scientific sense can give rise to complex changes in living organisms of the sort documented in the fossil record. For obvious reasons such a test is not practicable.<
How would you distinguish between a mutation "known to be random in the scientific sense" and one that is not? There are lab-generated mutant fruit flies that reverse a key feature that makes them flies (2 versus 4 wings) and a key feature of major groups of arthropods (appendage type and number). I.e., using the standard criteria for identifying crustaceans versus insects versus arachnids, the mutant fly is none of these, reminiscent of the condition observed in the Cambrian radiation, when these were not standardized.
>And what I meant by saying that "God indeed may skew the distributions" really should have been more like the following: If God determines a particular outcome, for that event the PDF collapses to a single value. In other words, God's momentary input changes the system momentarily from a probabilistic one to a deterministic one. So one needn't think of God as surreptitiously skewing distributions, but one might and should, IMHO, expect God to make his input felt now and then, as he sees fit.<
Is this different from any other mathematically random event? If I flip a coin, it ends up tails or heads or balanced on its side. Once I flip a coin and get tails, the probability that the outcome was tails is 100 percent.
Part of the issue is the extent to which we assume that everything is determined.
Dr. David Campbell
Old Seashells
University of Alabama
Biodiversity & Systematics
Dept. Biological Sciences
Box 870345
Tuscaloosa, AL 35487-0345 USA
bivalve@mail.davidson.alumlink.com
That is Uncle Joe, taken in the masonic regalia of a Grand Exalted Periwinkle of the Mystic Order of Whelks-P.G. Wodehouse, Romance at Droitgate Spa
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