Cladistics is the non-hierarchical way of understanding the history of life. It is the science of comparison. In Ordinary Time, we can understand the history of life as a succession of generations, but in Deep Time, in the vast stretches of millions of years, there are only a few scattered fossils to guide us. It is almost impossible to determine which fossil came first, or second, or third. For instance, could the earliest known bird, Archaeopteryx, have evolved to flight independently from other birds? The cladistic revolution has reinvented the scientific history of the world by comparing fossils in a way that allows us to predict what a particular original common ancestor was, even what its DNA was, without the straightjacket of a hierarchical tree of life.Henry Gee, who was on the scene in London while the revolution was taking place in the 1980s, takes us to the real Jurassic Park where scientists are trying to identify our common ancestors. He also shows that this breakthrough will be our guide to life on another planet. Further, when we populate other planets and split into a multitude of new species, cladistics will define what it truly means to be human. And in the meantime, In Search of Deep Time will bring to the world the essential tools for understanding areas as diverse as whether birds evolved from dinosaurs and the curing of bizarre new viruses.