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Origination of Organismal Form: Beyond the Gene in Developmental and Evolutionary Biology (Gerd B. Müller (Muller) and Stuart Newman)

Chapter 1:

Origination of Organismal Form: The Forgotten Cause In Evolutionary Theory

Evolutionary biology arose from the age-old desire to understand the origin and the diver-sification of organismal forms. During the past 150 years, the question of how these two as-pects of evolution are causally realized has become a field of scientific inquiry, and the standard answer, encapsulated in a central tenet of Darwinism, is by "variation of traits"and "natural selection." The modern version of this tenet holds that the continued modification and inheritance of a basic genetic tool kit for the regulation of developmental processes, directed by mechanisms acting at the population level, has generated the panoply of organismal body plans encountered in nature. This notion is superimposed on a sophisticated, mathematically based population genetics, which became the dominant mode of evolutionary biology in the second half of the twentieth century. As a consequence, much of present-day evolutionary theory is concerned with formal accounts of quantitative variation and diversification. Other major branches of evolutionary biology have concentrated on patterns of evolution, ecological factors, and, increasingly, on the associated molecular changes. Indeed, the concern with the "gene" has overwhelmed all other aspects, and evolutionary biology today has become almost synonymous with evolutionary genetics.

These developments have edged the field farther and farther away from the second initial theme: the origin of organismal form and structure. The question of why and how certain forms appear in organismal evolution addresses not what is being maintained (and quantitatively varied) but rather what is being generated in a qualitative sense. This causal question concerning the specific generative mechanisms that underlie the origin and innovation of phenotypic characters is probably best embodied in the term origination, which will be used in this sense throughout this volume.

Full text of Chapter 1 available at:

http://homepage.univie.ac.at/gerhard.mueller/pdfs/2003Origin.pdf

Amazon.com link:

http://www.amazon.com/gp/product/0262134195/002-9464151-6378437?v=glance&n=283155

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