Natural selection is commonly interpreted as the fundamental mechanism of evolution. Questions about how selection theory can claim to be the all-sufficient explanation of evolution often go unanswered by today's neo-Darwinists, perhaps for fear that any criticism of the evolutionary paradigm will encourage creationists and proponents of intelligent design.In Biological Emergences, Robert Reid argues that natural selection is not the cause of evolution. He writes that the causes of variations, which he refers to as natural experiments, are independent of natural (...) selection; indeed, he suggests, natural selection may get in the way of evolution. Reid proposes an alternative theory to explain how emergent novelties are generated and under what conditions they can overcome the resistance of natural selection. He suggests that what causes innovative variation causes evolution, and that these phenomena are environmental as well as organismal.After an extended critique of selectionism, Reid constructs an emergence theory of evolution, first examining the evidence in three causal arenas of emergent evolution: symbiosis/association, evolutionary physiology/behavior, and developmental evolution. Based on this evidence of causation, he proposes some working hypotheses, examining mechanisms and processes common to all three arenas, and arrives at a theoretical framework that accounts for generative mechanisms and emergent qualities. Without selectionism, Reid argues, evolutionary innovation can more easily be integrated into a general thesis. Finally, Reid proposes a biological synthesis of rapid emergent evolutionary phases and the prolonged, dynamically stable, non-evolutionary phases imposed by natural selection. (shrink)

Conrad Hal Waddington was a British developmental biologist who mainly worked in Cambridge and Edinburgh, but spent the late 1930s with Morgan in California learning about Drosophila. He was the first person to realize that development depended on the then unknown activities of genes, and he needed an appropriate model organism. His major experimental contributions were to show how mutation analysis could be used to investigate developmental mechanisms in Drosophila, and to explore how developmental mutation could drive evolution, his other (...) deep interest. Waddington was, however, predominantly a thinker, and set out to provide a coherent framework for understanding the genetic bases of embryogenesis and evolution, developing his ideas in many books. Perhaps his best-known concept is the epigenetic landscape: here a ball rolls down a complex valley, making path choices. The rolling ball represents a cell’s development over time, while the topography represents the changing regulatory environment that controls these choices. In its later forms, the role of each feature in the landscape was controlled by the effects of sets of interacting genes, an idea underpinning contemporary approaches to systems biology. Waddington was the first developmental geneticist and probably the most important developmental biologist of the pre-molecular age. (shrink)

Conrad Hal Waddington integrated genetics with embryology and evolution by formulating and providing experimental evidence for the mechanisms of canalization and genetic assimilation in the context of stabilizing selection, and by fostering an epigenetic rather than the prevailing gene-centered view of embryonic development and of evolutionary change in development and adult form. Waddington saw phenotypes as processes, not static structures and behaviors. Trained in geology at Cambridge, Waddington turned to experimental studies on the chemical nature of the primary organizer and (...) developed the concepts of evocation and individuation as separable components of embryonic induction. A move after WW II to Edinburgh provided Waddington with his professional home for the rest of his career, during which he integrated genetics and development into an evolutionarily relevant discipline. Our conception of embryonic development as a highly integrated series of canalized pathways owes much to Waddington’s development of the concepts of canalization, chreods, epigenetics, and the epigenotype. The integrated, heritable, epigenetic organization of embryonic development is Waddington’s lasting legacy to development. He demonstrated organismal response to environmental change and hidden genetic variation, integrated environmental responsiveness into heritable change in response to selection, and coupled development, environment, and evolution. (shrink)