Book Review: Echoes of Life: What Fossil Molecules Reveal about Earth History.

The year 1936 marks the beginning of organic geochemistry. It started with Alfred Treibs’ discovery of porphyrins in petroleum; compounds that closely resemble chlorophylls in plant matter. Another 25 years would pass before scientists recognized that these compounds, known as biomarkers, could reveal insights into the evolution of plants and animals spanning a time frame measured in billions of years.

The striking similarities between cholesterol and sterane.

Echoes of Life weaves a complex fabric of stories, peppered with personal details, that describe the emergence of analytical techniques; mainly GC-MS. The authors are a mix of organic geochemist, founding father of biomarker research and a marine chemist/novelist that draw on a variety of perspectives and experiences. Echoes of Life is a well written, digestible story rather than a textbook.  One of its enduring facets is the ability to eloquently describe the required transition of geochemist to analytical chemist; a necessity to crack the origins of oil. The book starts as a disjointed collection of stories from finding “life” on the moon to botanists studying leaf waxes. Using mass spectral interpretation it was evident that cholesterol could be found in oil in the modified form of steranes and hopanes. They were “stripped of their double bonds and oxygen containing functional groups reduced to their bare carbon skeletons.” The book follows researchers from around the world arriving at the same conclusion from various fields using different techniques. Described as, “a tribe of scattered chemists using the new technique of ‘coupled GC-MS’ and coming to the same conclusion.”

The Deep Sea Drilling Project (DSDP) revealed chemical traces of algae, zooplankton and microbes that proved to be a chemical chronicle of the last 150 million years. The keys to understanding the history of earth, its climate and life were locked in these biomarkers. For instance the degree of unsaturation in algae’s lipids increased systematically with an increase in temperature. Dialkyl ketones containing 37 to 39 carbon atoms were analyzed to determine the number of double bonds remaining. Combining age of sediment and dialkyl ketone data, scientists were able to estimate regional global temperatures.

Sterane and Hopane patterns in MC252 Crude (shaded areas) by GC-MS SIM using an Rxi-5Sil MS 30m x 0.25mm x 0.25µm film column.

The story is a combination of thousands of scientific papers, hundreds of interviews and many anecdotes as a mechanism for moving the story forward. Reflected in these pages is an insatiable curiosity that defines science. This book is a journey of discovery, the human spirit and the quest to understand our surroundings. It is a trip worth taking.

Echoes of Life: What Fossil Molecules Reveal about Earth History. Susan M. Gaines, Geoffrey Eglinton and Jurgen Rullkotter. Oxford University Press, 2008. 376 pp. (ISBN 9780195176193 cloth).

Check out Michelle’s work on oil identification: Fingerprinting Crude Oils and Tarballs using Biomarkers and Comprehensive Two-Dimensional Gas Chromatography

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