Fig. 1

The standard view of evolutionary change. Using successions of fossil scallops as an example, the diagram shows the division of an ancestral species into separate lineages that are then further transformed gradually into descendant species. This drawing, an oversimplification of Darwin’s own views, was nonetheless the prevailing image of what evolution through time “looks like”—the image I learned in my early training as a paleontologist (Steve Thurston, American Museum of Natural History—“AMNH”)