Many similes have been used to introduce us to our genome; our DNA. It's a plan. It's a recipe. It's a blueprint. It's a code. Ridley shows how these metaphors miss the point - they're all too fixed to compare with the dynamics of the fundamental molecule of life. He shows how our genome, indeed, the genome common to all life, uses the same elements to say many things. Instead of terms identifying fixed elements, he suggests the image of language. The genome has a limited lexicon of phrases with which to build bodies and personalities, yet manages an immense variation in the results. How like a chimpanzee are you?, he asks. Depending on how you make the comparison - very little or very much. If you count the entire number of "base pairs" making up chimpanzees and humans, the difference is minimal - perhaps 30 thousand out of 3 billion. If, instead, you visit the zoo [or, better, Gombe] the differences are striking.
In Ridley's view, the striking differences are due to "word order" contained in the genome. All the words are essentially the same, but different locations and different interactions produce different characteristics. Including behaviour. In the six or seven million years since the chimpanzee-human line diverged, lifestyles, diet, social structure and living environment have helped guide how the genome produces a body and how that body will likely act in a given situation. Environment and the genome, then, are in a constant interactive flux. They feed signals through the organism to determine whether the organism will survive and reproduce. Nature isn't in the driver's seat, and if we fail to learn or adapt to the vagaries of environment, we won't survive to have descendants. Nature, then, is achieved via nurture.
All this should seem self-evident in today's world, but Ridley shows we have yet to fully understand and accept our role in Nature. There are few writers as articulate and expressive in dealing with these issues as Ridley. His grasp of the science involved is firm, yet he maintains a conversational tone throughout the narrative. While you will encounter much that is new to you in this book, you may close it [the first time], confident that his explanations have neither overwhelmed you nor left you unsatisfied. Of course, as Ridley points out, there is much work remaining in understanding the genome's impact on life. With luck, this book may impel others to follow his lead and uncover more of life's mysteries. [stephen a. haines - Ottawa, Canada]