Darwin did NOT say “Random Mutation”
Lynn Helena Caporale, St John’s College of Liberal Arts and Sciences, Institute for Core Studies
The Theory of Evolution (TofE) states that selection acts upon heritable variation that affects fitness. The application of the TofE to biological evolution was incomplete in the 19th Century because, as Darwin himself recognized, the source of genetic variation was not understood. When the “Modern Synthesis” incorporated the concept of genes and mutation into evolutionary theory the term “random mutation” incorrectly became associated with Darwin himself and the TofE. However, simply due to biochemistry, the probability of distinct types of genetic change varies along a DNA sequence. Because selection acts upon heritable variation, it acts upon variations on mutation much as it acts on beaks and wings; thus the probability of distinct classes of genetic variation can become aligned with the potential consequence to survival of that type of mutation at that site. Further, since enzymes affect the generation and repair of variation, different classes of mutation can be regulated, for example under conditions of stress (this should not be confused with the concept of directed mutation.) The observation that mutation is not random deepens, rather than contradicts, our appreciation of the power of natural selection. As illustrated by the rapid variation of certain pathogen surface antigens, the evolutionary success of a lineage may result from its being efficient at exploring variation that is aligned with the nature of challenges and opportunities the lineage has faced repeatedly during evolution in the context of an environment that is not random. Further, discussions of TofE in popular culture often focus on terms such as “random mutation” and “descended from apes,” while confusing victory in hand-to-hand battle with fitness. However, cooperation often contributes to fitness, through communication, sharing of DNA and exchanging metabolites. Since perfect but unchanging adaptation to a specific environment is risky (because the environment can change), diversity in a population, including human populations, also contributes to fitness.