Evolution and Development III: Cause & Effect

Evolution has resulted in organisms that develop. For a long time the processes of evolution and development have been theoretically and empirically largely independent. This was epitomized by the gene selectionist view of evolution, which rendered the process of development largely epiphenominal to the evolutionary business of evolving the genome. However, there is now a growing awareness that an understanding of development is essential to a complete understanding of evolution and vice versa. This session addresses what this 'developmental synthesis' may contribute and some difficulties that must be overcome for its success.

Organized by: Kelly Smith & Roger Sansom

Andre Ariew, University of Rhode Island
"Revisiting Ernst Mayr's Distinction Between Ultimate and Proximate Causes in Biology: 40 Years Later"

The year 2001 marks the 40th anniversary of Ernst Mayr's seminal paper, "Cause and Effect in Biology" where Mayr presented the most thorough articulation of his version of the ultimate vs. proximate cause distinction. Mayr's paper is rich yet conceptually confused at places. Out of the thicket of issues and non-starters I attempt to salveage and critique a workable distinction. My main thesis is that the ultimate/proximate distinction is not one that distinguishes between two causal processes, developmental and evolutionary, because evolution is not a causal process while development is.

Denis Walsh , University of Edinburgh
"The Unity of Biology: Natural Selection and Development"

There is a commonly-held view that natural selection is the central, unifying concept in evolutionary biology. Selection is the presumed cause of adaptation and, in turn, adaptation explains both the traits of individual organisms and the distribution of biological form. Development is significant only insofar as it constrains the efficacy of selection. I argue that this picture is mistaken on two counts: (i) Natural selection is not a force, as commonly supposed, nor, consequently, is it the cause of adaptations, and (ii) Developmental constraints are the causes of adaptations. Development constraint explains why natural selection realises adaptive evolution. This conception of the relation between natural selection and development is, I think, a novel one. It suggests that only an evolutionary theory that puts the principles of development at its centre can adequately account for the nature of adaptations and the distribution of form. [ E-mail author for copy of paper ]