Mechanisms of Evolution'

I am compelled to respond to Akbar F. Brinsmade's letter that attempts to refute the theory of evolution by natural selection (C&EN, Jan. 8, page 4). Brinsmade's arguments demonstrate confusion about the facts of scientific evidence and about the fundamental mechanisms of evolution.

Mendel's discoveries of inheritance and genetic segregation of traits actually complement Darwin's theory. Darwin himself wrestled with the mechanism of genetic diversity and inheritance. Mendel supposed that his observations could be explained by a passing down of a physical substance to progeny, which is preserved and serves as a basis for the physical traits. Today we know these are chromosomes. Had Darwin known of Mendel's findings, he would likely have published "The Origin of Species" faster and with more conviction and less doubt.

The fossil record does indeed provide evidence of evolution by natural selection. To say otherwise is to make a false statement. One common argument is that there are "holes," in the fossil record, but this is a misleading argument. Let's say that there are Homo sapiens and an ancestor that is common to the ape—there's a large gap in the fossil record. We discover a link—H. erectus. Now there are two holes, linking sapiens with erectus, and erectus with an ancestor common to the ape. We discover H. ergaster—now there are four holes. We discover five species of Australopithecus—now there are eight holes. You can see how the argument can feed itself when evidence is provided to negate it.

Furthermore, any fundamental understanding of genetics and biochemistry will support evolution and natural selection. The human genome contains repeats and modifications of genes that duplicated, expanded, and rearranged in evolutionary history to create increased complexity in both the number of proteins and types of protein interactions. Favorable changes survived; unfavorable ones did not. One need only compare amino acid sequences of related proteins across species or to examine expansions of protein families and one sees duplications and rearrangements of favorable protein domains across evolution. The evidence for evolution in biochemistry and genetics is stunning, beautiful, and mathematically elegant.

Brinsmade asks, "How can randomness produce the myriad of complex and integrated human elements and characteristics?" Natural selection is not random. The classic example of monkeys with typewriters illustrates. For monkeys to randomly type "To be or not to be," for all intents and purposes, they would be typing forever. But if correct letters were preserved from trial to trial (for example, whenever T was typed as the first letter or E, as the last), it has been shown this process would reduce the necessary time to a few hours. A computer randomly typing would take days, but with selection, it takes seconds. Finally, I would like to point out that the argument by personal incredulity against evolution provides no evidence.

Erick Tatro
Pittsburgh

Recent letters to C&EN fail to recognize a crucial aspect of the evolution and intelligent design controversy, namely, that neither accounts for the stunning advances in understanding the functioning of living tissues. Neither theory is useful for experimental biological science.

What do members of the public, who pay for the outstanding biology research, find valuable? The list of accomplishments would include discoveries of antibiotics to cure bacterial diseases, improvements of sanitation procedures for better public health, cures for cancers, vaccines, nutritionally improved foods, insecticides, recognition of the importance of DNA, cures for genetic diseases, and so on. None of these valued discoveries depended on historical biology, speculations about biological origins, or what happened over the billions of years since life appeared on our planet.

Not only do such speculations suffer from much ambiguity and lack of solid surviving evidence, but, most important, those theories do not guide the experimental biologist to the valued discoveries. Their main impact is in the areas of ancient history, theology, philosophy, and metaphysics—subjects that are important but of little heuristic value to experimental biological science, though they may, nonetheless, be a source of individual inspiration. This conclusion is clearly evidenced by the lack of Nobel Prizes for work in those nonexperimental fields, by pharmaceutical companies not having evolution divisions, and by medical school curricula not dwelling on biological origins.

We do not ask whether we are evolving; our bodies are constantly doing many ingenious things to avoid the kinds of drastic changes postulated for evolution. The highly successful experimental research that led to our present knowledge of how living tissues function to achieve these remarkable objectives is dependent on the use of new methodologies and instrumentations that have brought success to those explorations, not through immersion in the disciplines and speculations of historical biology.

Philip S. Skell
State College, Pa.