Mammals diversified in a new evolutionary radiation, as small businesses would today if every large corporation declared bankruptcy overnight. Many mammal species went big. Within half a million years, there were cow-size herbivorous mammals and equally large mammalian carnivores. There were also primates, members of the order of tree-dwelling, fruit-eating mammals from which we are descended. Though the first primates already existed in the world of dinosaurs, they flourished only after the dinosaurs had left the scene. There
