Sunday, December 11, 2005

In Defense of Evolutionary Science

(I wrote the following on Saturday in response to a creationist opinion piece in the newpaper "The Ithaca Journal." His letter is fairly typical of what you will often find in newspapers.)

This is in response to Harry Lockwood's "Evolution isn't Science" of Dec.10th, 2005.

The process of evolution is one of the most well-established discoveries of science today. Our knowledge of this process was originally built upon the existence of a hierarchy of categories of animals classified according to their similarities, the fossil record and embryology (all of which involve the "systematization of knowledge derived from observation") but, unlike stamp-collecting, reaches beyond what has simply been observed to arrive at causal explanations, make predictions, and meet the test of experience as empirical science always must.

Given the similarities which exist between fish and reptiles, reptiles and birds, and reptiles and mammals, land mammals and whales, transitionals were predicted which would show a mixture of attributes from the older, more ancestral form to the latter. In each case, a series of transitionals existing at different steps in the right chronological sequence along the suggested paths were found, including a creature which was half way between having a reptilian jaw and a mammalian jaw (something creationists declared impossible) -- bearing a double-jointed jaw which worked.

Today we are able to observe the evolution of viruses and bacteria. We are able to modify their environment and see how species evolve in order to adapt to it, how they acquire resistance to antibiotics. In the mid-1980s, Hall removed three different genes from a single bacterium which were necessary for the digestion of lactose, whose descendants then re-evolved genes for such digestion through a process of stress-induced hypermutation and natural selection. A similar process of hypermutation and natural selection is involved in our own adaptive, B-cell based immune system which responds to new pathogens. Those who declare evolution through mutation and natural selection impossible owe their very lives many times over to the simple fact that such a process is possible and that it works.

Lockwood invokes the Second Law of Thermodynamics (without naming it) which tells us that the disorder within a closed system will never decrease. What he does not realize is that the earth is not a closed system. Order may rise out of chaos like a storm growing at sea. Organisms can grow and multiply, and species may evolve and branch into new species -- because this increasing order is more than balanced by the energy released in the process through which the sun consumes itself.

He argues that virtually all mutations are harmful, failing to realize that such harmfulness can occur in degrees and is relative to the genes which already exist in genetically diverse populations due to earlier mutations and genetic drift. Natural selection will eliminate the more harmful mutations, and what may have been slightly harmful in one context could be quite beneficial in combination with other genes or within later environments. Natural selection does not eliminate all but the fittest, but acts like gravity upon a fluid pool of genetic diversity which has the capacity to flow somewhat randomly due to the local currents of genetic drift, but in the general direction of greater adaptation.

Evolutionary biology is a strong yet growing branch of empirical science supported by a vast body of evidence which is growing at an ever-increasing rate. For example, we are able to identify the proviruses left by retroviral infections tens of thousands or even tens of millions of years ago in the genomes of many different species (30,000 in the human genome alone). When we compare the vast genomes of different species, we find that closely-related species have the same retroviral insertions at the same exact points.

This isn't random: the insertions are at the same exact point because the insertions occurred in their common ancestor. Moreover, the diagrams which are constructed strictly on the basis of such insertions match the diagrams based upon the evidence which existed prior to any knowledge of viruses or DNA. Nevertheless, such insertions provide us with far more precise and detailed knowledge than was available before. Similarly, closely related species will often share the same broken genes ("pseudogenes") which are broken in the same way -- such as chimps and humans whose ancestors lost the ability to produce their own vitamin C.

The persistence of creationist beliefs in the face of such overwhelming evidence stands as a monument to an educational system which fails to prepare students for an increasingly scientific world. It stands as a testament to the willful ignorance of those who would prefer Ptolemy's geocentric vision of the solar system over the Copernican if they realized that it conflicted with a blindly literal interpretation of the Bible. Those who wish their children a better future should insure that their young minds are not enslaved by such senile, dogmatic fundamentalism, see to it that the educational system is repaired, and that such well-supported science receives the focus which it deserves.

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