Stephen Jay Gould, Pere Alberch e il modello-orologio dell’eterocronia: incontro e divergenza alle origini di evo-devo

Stephen Jay Gould's book Ontogeny and Phylogeny (1977), recently translated into Italian, is unanimously considered as one of the founding texts of evo-devo. Pere Alberch, another pioneer of the field, was early stimulated by reading Gould's book. In particular, he got into the "clock model", an image devised by Gould to organize thinking and terminology about heterochrony (i.e., evolutionary change of the timing of developmental processes). Alberch engaged Gould in a formalization of the clock model, which they published in 1979. After that work, however, the two authors diverged. Alberch noticed inconsistencies in the view of development they had adopted, and moved on towards a more dynamic view. Gould didn't follow this route, and remained largely insensitive to Alberch's work. Reflection on this debate allows for a clarification of the assumptions of different approaches to ontogenic development. Particular attention is given to the dynamical systems approach, grasped by Alberch in the mid 1980s, and regarded as very coherent and promising in today's evolutionary developmental biology.