DNA evidence not only solves crimes - if you know how to read it, it can also reveal the history of life on earth. This fast-paced book guides the general reader on a tour of the DNA record left by three billion years of evolution to see how the fittest were made. And what a eye-opening tour it is - one featuring immortal genes, fossil genes, and genes that bear the scars of past battles with terrible diseases. Natural selection eliminates harmful changes and embraces beneficial ones, and each change leaves its signature on a species' DNA codes. For example, the Antarctic ice fish today has no red blood cells; yet a fossilized gene for hemoglobin remains in its DNA, showing that the fish has adapted over 55 million years by losing the red blood cells that thicken blood and make it harder to pump in extreme cold.The fish has developed other features that allow it to absorb and circulate blood without hemoglobin. Carroll points out that by examining the DNA of these ice fish species, it's possible to map its origins as well as the history of the South Atlantic's geology. He also uses dolphins, colobus monkeys, pigeons, fruit flys and microbes to demonstrate how deeply evolution is etched in DNA.