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Theoretical Implications of Convergent Evolution: The Tape of Life Reconsidered

PI(s): Russell Powell (Boston University (Boston,MA))
Start Date: 17-Mar-2015
Keywords: adaptation, adaptive radiation, evolutionary theory, macroevolution

Stephen Jay Gould argued that replaying the ‘tape of life’ would result in radically different evolutionary outcomes. Some biologists and philosophers of science have appealed to the ubiquity of convergent evolution—the independent origination of similar forms and functions—as evidence against Gould’s thesis. However, the contingency question is underdetermined by data on convergent evolution as it has thus far been collected and analyzed. Convergence proponents have lumped causally heterogeneous types of convergence into a single basket, presenting the total dataset as evidence against an ultimately erroneous interpretation of Gould’s view. As a result, the ‘critique from convergent evolution’ has failed to engage with key elements of the ‘radical contingency thesis.’ In the first part of this conceptually synthetic project, I develop a targeted theoretical approach to convergent evolution that enables us to distinguish evolutionarily robust iterations from those that do little to undermine, and may in fact reinforce, the Gouldian view of life. In the second part, I examine the contingency question in relation to a particular subset of macroevolutionary outcomes, namely the emergence of minds. Here I explore the evolutionary replicability of image-forming sensory modalities (including vision, echolocation, and electrolocation) and their connection to complex forms of behavior, cognition and consciousness. Drawing upon philosophical discussions of contingency, causation, constraint and cognition, this analysis will shed light on what convergent evolution tells us about constraints on the history of life as it has unfolded on Earth, and how it might do in other nooks and crannies of the habitable universe.