Evolutionary Retrodictions

I agree with many of Avraham Sonenthal's points (The Scientist, July 7, 1997, page 10) regarding your recent article "To Effectively Discuss Evolution, First Define Theory" (R. Lewis, The Scientist, May 12, 1997, page 13). I disagree, however, that all science is experimental or that the extrapolation of evolution into the distant past is completely conjectural. Tests of theories can be observational and employ not just predictions but also retrodictions. Retrodictions are extrapolations into the past about things that should be (but have not yet been) found in the geological, paleontological, or archeological record if a theory is correct. Darwin, for example, retrodicted that many intermediate forms would be found in the fossil record linking human beings and other primates and that similar intermediates would be found linking modern horses with primitive mammals. We must remember that, at the time, no such fossils were known. Obviously, these retrodictions have proved to be accurate. One of the reasons that creationism fails to qualify as a scientific theory is that its retrodictions, as embodied in the accounts of Genesis in the Bible, are often not consistent with the geological and fossil record. Moreover, as far as I know, no "creation scientist" has provided any detailed retrodictions to test beyond Genesis. The point is simple: Evolutionary theory does tell us what to expect to find in our investigations of historical materials, and observation has almost completely validated these expectations. Creationism does not tell us what to look for in the historical record and so provides no tests of itself. I would also like to answer Sonenthal's challenge concerning the modern utility of evolutionary theory. I could give many examples, but I will limit myself to three of very different types. First, camouflage, in which an animal evolves to mimic its environment, and indeed all types of mimicry, were discovered and explained by evolutionists including Abbot Thayer, Darwin, H.W. Bates, and Fritz Mueller. Abbot Thayer (ca. 1890) immediately suggested the application of camouflage to warfare, resulting in the abandonment of brightly colored uniforms that had been the standard to that time in favor of earth-colored ones by World War I. This innovation has changed the face of warfare (and hunting) and continues to be an area of avid research by the military. My second example of the utility of evolutionary theory is evident in the use of literal evolution to produce and select novel molecules in combinatorial libraries of chemical compounds such as DNAs, RNAs, peptides, and related organic polymers. For example, polymerase chain reaction (PCR) has been modified to increase the rate of mismatches so as to increase the number of new sequences rather than to produce accurate reproduction of a target sequence. The randomized sequences are then passed over target receptors and screened for desired activity (artificial selection). These are among the hottest areas of research in the pharmaceutical and chemical industries. Finally, computer programmers have been using so-called genetic algorithms for more than a decade to produce more and more sophisticated "artificial intelligence" programs. These genetic algorithms are modeled exactly on evolutionary theories, such that the final program has been arrived at by a process of "survival of the fittest." Such programs have been used to help physicians make better diagnoses, chemists make better guesses as to the properties of their chemicals, economists to predict the course of the economy, and so forth. Sonenthal is correct that no company seems to have a division specifically called "Evolutionary Applications," but those applications are, in fact, there-they just appear under other names. Robert Root-Bernstein Professor of Physiology Michigan State University East Lansing, Mich. 48824-1024 E-mail:

Evolutionary Retrodictions

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