Forschungslaboratorium am Goetheanum, Hügelweg 59, CH-4143 Switzerland
The appearance of adaptive mutations in bacteria raises basic questions about the genetic theory of spontaneous mutation and hence the concept of the generation of biological variation. Adaptive mutations were observed in bacteria exposed to selective conditions during the stationary phase of growth in the absence of DNA replication. Both anabolic and catabolic traits were affected. None of the classical explanations, which depend on errors and irregularities during the replication process, is able to account for these mutations. Various observations suggest new mechanisms for the generation of genetic variation. The theory of adaptive mutations paves the way for the introduction of complementarity in modern genetics.
Theories of adaptive mutations elaborated before the era of molecular genetics argue strongly for holistic approaches to life and heredity. They make a revision of the current concepts of reductionist biology necessary. A synthesis is presented that considers the function of spontaneous as well as adaptive mutations in the development and evolution of organisms. Both forms of mutations reflect the fundamental quality inherent among all living beings; i.e. self-relation and world-relation.
According to modern theories of heredity and evolution the tremendous variation amongst living organisms comes about in two ways, namely through spontaneous mutation and through chance hybridisation during sexual reproduction. An overwhelming number of publications provides evidence for chance variation. Because of this chance variation and DNA molecular replication (doubling) processes, which produce changes in the genetic make-up, spontaneous mutations pass undisputed as the driving force of variation and thus speciation. According to this view, in a second step, choice or selection determined by the environmental conditions sees to it that only the most fitting forms survive, thus limiting the variation which arises.
In spite of the many confirmations of the theory based on spontaneous mutation this article aims to outline and provide support for another possible theory, one in which the environmental conditions do not merely select, but direct and bring about variation. This is not intended to cast doubt on the reality of spontaneous or chance mutation, but rather to challenge its claim to absolute and exclusive validity.
The current situation in modern genetics is like that which prevailed in physics at the beginning of the 20th century. Just as at that time wave and particle theories of light were shown to be complementary views, it will be demonstrated that the present theory of chance evolution of organisms must be enlarged to include a complementary one, namely directed evolution. The theory of spontaneous mutation is placed beside that of adaptive or selection-induced mutation. Which of the two types of genetic change is realised depends on the physiological circumstances and the environment