ARTHUR, W; University of Sunderland: Beyond constraints and spandrels: the effect of development on the direction of evolution

Is evo-devo heretical? In other words, does it have anything to say about the factors that determine the directions that evolution takes, which might challenge the supremacy of natural selection? Here I examine these questions and take the following view. Both neo-Darwinism and evo-devo are, from a conceptual perspective, heterogeneous. Not all the proponents of either approach share the same philosophy on the causes of evolution’s directionality. ‘Hard’ and ‘soft’ versions of each can be discerned. The hard versions are incompatible, as can be seen by comparing the views of pan-selectionists with the views of those who come perilously close to being ‘pan-constraintists’. However, the softer versions of the two outlooks are perfectly compatible, because it is possible to look upon the direction that evolution takes as being determined by the interaction between developmental bias (NB not just ‘constraint’) and natural selection. I examine the form this interaction may take, and conclude that the major challenge ahead is the quantification of patterns of biased variation in natural populations and the stucture of adaptive landscapes.