In 1936 a German chemist identified certain organic molecules that he had extracted from ancient rocks and oils as the fossil remains of chlorophyll--presumably from plants that had lived and died millions of years in the past. It was another twenty-five years before this insight was developed and the term "biomarker" coined to describe fossil molecules whose molecular structures could reveal the presence of otherwise elusive organisms and processes.Echoes of Life is the story of these molecules and how they are illuminating the history of the earth and its life. It is also the story of how a few maverick organic chemists and geologists defied the dictates of their disciplines and--at a time when the natural sciences were fragmenting into ever-more-specialized sub-disciplines--reunited chemistry, biology and geology in a common endeavor. The rare combination of rigorous science and literary style--woven into a historic narrative that moves naturally from the simple to the complex--make Echoes of Life a book to be read for pleasure and contemplation, as well as education.