Stasis — Genome Repair — A Counter Point to Mutation?
- Evolution implies gradual changes occur over time, but is there anything to suggest resistance to change? That is, do biological beings exhibit any traits to suggest there are mechanisms at work to maintain a species over time?
- Do many, all, or any species once established in time past, as evident in the fossil record, show a propensity to change from that time forward?
One of the interesting points to glean from plants and any animal species that are preserved in the fossil record, is their maintenance over time. You can go to a botanical garden today and see a plant called a cycad. You might think of these as something looking like a dwarf palm trees, but that's a close approximation for a description of a remarkably old species. Fossils bearing impressions of cycads of long ago suggest this plant type has changed very little over time. In fact, some features (for example the numbers of stomata or 'pore structures' in the leaf surfaces) can be examined in present day and ancient fossil impressions to reveal something about differences in growing conditions. But over all, the species has changed very little.
Stasis is defined in terms of "inactivity, equilibrium, standing or stoppage" and in the case of biological life, this means that a form or type (species) exists over time and maintains no apparent change.
Examples of living fossils include the horseshoe crab and lungfish. Dr. Denton provides an interesting discussion concerning the lungfish in Chapter 5 of 'Evolution' (ETC). Here the living form reveals something that the typical (skeletal, bony) fossil cannot show us. The living fossils' internal organs (which are a full compliment of otherwise absent features in a typical fossil) can be considered with respect to the earliest members of the same species. Lungfish and other examples, as explained by Denton, appear to reveal a combination of traits (mosaics) that help little to identify these organisms as intermediate forms and that gaps between groups remain due to the 'living data' that compliments the ancient fossil finds.
THEY DON"T SHOW CHANGE
The real question might not be living fossils prove evolution, but instead reveal evidence for fixity of type ... stasis ... that is, a lack of change over time. What then of natural selection, mutations, chance, and random variation for any species that appears now not to have changed or to have changed very little?
A number of deep sea fish species and many invertebrates, both terrestrial and aquatic, have been discovered over the past century but all of them have been very closely related to already known groups, and in the few exceptional cases, when a quite a new group of organisms has been discovered, it has invariably proved to be isolated and distinct and in no sense intermediate or ancestral in the manner required by evolution. Denton (ETC) Page 159
DNA and ERROR Correction
Take a minute to consider what occurs at the molecular level. If some species show little to no change over time, how do they maintain themselves? We know mutations occur. Sometimes DNA sequences are not 'read' perfectly. If there is error correction taking place, could such an incredible and marvelous cell function be created by the chance mechanisms often attributed to evolution?
Perhaps the best way to appreciate what does occur at the DNA and cell level is to read about how proof reading of DNA actually does occur in cells of living organisms. After that, we can sit back and reflect on the complexity and even wonder how such function could have been created in the first place!
The 3'_5' exonuclease activity plays a critical role in replication: it allows the enzyme to proofread the new DNA and cut out any mistakes it has made. Although the polymerase reads the sequence of the old DNA to produce new DNA, it turns out that simple base paring allows about one mistake per thousand base pairs copied. Proofreading reduces errors to about one in a million base pairs. The question for design theorists is whether proofreading exonuclease had to be present in the very first cell. That is, could the first cell, with its required complement of genes coded for by DNA, have successfully reproduced for a significant number of generations without a proofreading function? Behe (MC) Page 187
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When the chromosomes duplicate they don't do a perfect job of copying the DNA. They make about one error every 10,000 base pairs they copy [Darnell et al. 1986]. That's the error rate of a typist if he made one error every five pages. That error rate might be good enough for the office, but it's not good enough for genetic transcription. The genetic information has to be copied much more accurately than that to keep the errors from building up over the generations.
To reduce the errors, the cell proofreads the DNA and corrects any errors it made in replication. But a few errors remain even after the proofreading. They are known as copying errors, or single-nucleotide substitutions. They are mutations belonging to a class known as point mutations. They are few enough for the species to tolerate. With the proofreading, the copying has a very low error rate from one in a billion to one in a hundred billion. One error per hundred billion would be like one error in a fifty million pages of typescript. Fifty million pages are the lifetime output of about a hundred professional typists. And that's some proofreading! The cell, or organism, can allow this small error.*
[* Most evolutionists hold that these errors even play a positive role; they look on these errors as the source of the variation in neo-Darwinian theory needs. I disagree; I think these small errors just represent the limit of the accuracy with which DNA can be copied. Although I concede that they might play a role in small-scale evolution, I hold that they play no positive role in large-scale evolution. As we shall see in the following chapters random variation cannot lead to large-scale evolution.] Spetner (NBC) Page 38
Quotations from "Mere Creation" (MC) edited by William A. Dembski are used by permission of InterVarsity Press, P.O. Box 1400, Downers Grove, IL 60515. www.ivpress.com All rights reserved. No portion of this material may be used without permission from InterVarsity Press.
Quotations from " Not By Chance " (NBC) written by L. Spetner, are used by permission granted by Dr. Lee Spetner.
Writer / Editor: Dr. T. Peterson, Director, WindowView.org>