Time as imagery
The abstract imagery of time is primarily used in two ways. First, Ridley explains the development of human understanding through time, showing that through time, the scientific method was used to develop working theories about human biology (and plant/animal biology as well) until certain scientists finally discovered DNA. Science is shown to work through time because of the scientific method. Secondly, the reader is asked to consider epic swathes of time through which evolution might occur.
Science as a method
The book is very clear in its depiction of the scientific method. Through hypothesis, testing, and collaboration within a scientific community, humans have been able to understand more about biology than was previously possible. This is important, because the future of human insight depends on our continual support of the scientific method. Ridley discusses such communities in the book, especially the Human Genome Project.
Microbiology and imagery
Since DNA and cellular biology are too microscopic for humans to perceive directly, this book resorts to imagery, defining and describing various biological facts. The book helps the reader to correctly imagine cells, DNA, the creation of new animal life through sexual procreation of parents, and so on. The imagery is scientific and concrete, because these facts have been examined in laboratories around the world throughout time.
Humans and animals
The use of imagery is critical in helping the reader reframe their opinion of human beings. Instead of identifying humans for what makes them different from other animals, the book shows through scientific fact that animal imagery is the correct imagery for understanding a human being. A human is an animal; they are not "like" an animal, they literally are an animal. This important imagery is helpful, because by correctly understanding this, new medical breakthroughs are possible that were not available in the past.
