The Ancestor's Tale: A Pilgrimage to the Dawn of Evolution

by Richard Dawkins

The Big Bang Model, in its extreme form, sees a single mammal species surviving the K/T catastrophe, a sort of Palaeocene Noah. Immediately after the catastrophe, the descendants of this Noah started proliferating and diverging. On the Big Bang Model, most of the rendezvous points occurred in a bunch, just this side of the K/T boundary—the backwards way of viewing the rapidly divergent branching of the Noah’s descendants. 2. The Delayed Explosion Model acknowledges that there was a major explosion of mammal diversity after the K/T boundary. But the mammals of the explosion were not descended from a single Noah, and most of the rendezvous points between mammal pilgrims predate the K/T boundary. When the dinosaurs suddenly left the scene, there were lots of little shrew-like lineages who survived to step into their shoes. One ‘shrew’ evolved into Carnivores, a second ‘shrew’ evolved into primates, and so on. These different ‘shrews’, although probably quite similar to each other, traced their separate ancestry deep into the past, eventually to unite way back in the Age of Dinosaurs. Those ancestors followed, in parallel, their long fuses into the future through the Age of Dinosaurs to the K/T boundary. Then they all exploded in diversity, more or less simultaneously, when the dinosaurs disappeared. The consequence is that the concestors of modern mammals long predate the K/T boundary, although they only started diverging from each other in appearance and way of life after th...