Principles of Evolution pp 1-41
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This introductory section serves as a summary of overarching concepts, universal features, recurrent puzzles, a common language, and striking parallels between units of life, ranging from simple to complex organisms. We start with a short chronology of evolution, since nowhere else in this book is the historical path of evolution followed. An underlying common methodology of all articles here is reductionism. The section on reductionism illustrates the great success of this approach with examples from physics and biology, including also a hint on its abuse when it is pushed to extremes. Guided by the success of reductionism, one may wonder whether there is a universal theory of evolution. Such a universal theory does not exist, but striving for universal laws makes sense when it is based on striking similarities between seemingly very different realizations of systems whose dynamics is governed by the very same mechanism. In this case recurrent behavior goes beyond a superficial analogy. Again we illustrate the concept of universality with examples from physics, but also indicate limitations in view of universal equations. Beyond universal laws, universal principles of organization may be at work. One such overarching principle is self-organization. In addition to its known successful application in various disciplines such as physics, chemistry, and cell biology, it leads to a challenge for future research on how far one can further stretch this concept to explain all complex outcome of evolution as self-organized. Common to the various examples of self-organization in later chapters is the emergence of a complex structure out of less structured or even random initial conditions. The very choice of initial conditions is often the art of the game. In the spirit of reductionism, the initial conditions should involve as little structure as possible to let the complex structure emerge from the very rules of evolutionary processes. This demand may lead to “chicken and egg”-like dilemmas. Such dilemmas appear in many facets in and outside natural science. They are intimately related to questions of origin, in particular the origin of life. Questions of life’s origin go along with an estimate of the date when first forms of life appeared. Therefore another evocative topic concerns the very probability of life coming into existence in the course of evolution. This relates to the tension between contingency and necessity, stochastic fluctuations and deterministic rules. The question arises as to whether, if we were able to rewind the tape of evolution and replay it again, contingency would lead to minor differences or even changes in the gross features of the evolutionary outcome. Rewinding the whole tape is science fiction, but rerunning short sequences of this tape is reality. We collect a few such attempts from contemporary lab experiments under controlled initial conditions or related computer simulations. Without mathematical modeling, seemingly natural extrapolations lead to premature or even false conclusions on the evolutionary potential. Therefore we disentangle the reduction of complexity from misleading oversimplifications and conclude with an appeal for mathematical modeling also in biology. Finally we summarize all chapters of this book to embed their content in the context of this book.