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1 September 2009 Echoes of Life: What Fossil Molecules Reveal about Earth History
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In her first book, Carbon Dreams (2001), Susan Gaines combined fact and fiction to depict the life and struggles of a female geochemist as her career developed. The book portrayed the scientific world in both positive and negative ways by highlighting the passion that scientists have for their research, the difficulties and frustrations of finding funding, and the politics of scientific discovery. In her second book, Echoes of Life, with coauthors Geoffrey Eglinton and Jürgen Rullkötter, Gaines once again explores the trials and tribulations of scientific discovery, but this time the story is nonfiction, and the real-world context is the inception and growth of biomarker research and geochemistry.

The science of biomarkers evolved while oil exploration was in high gear, the oceans depths were being scoured, and interplanetary dust and moon rocks were a vast mystery. Throughout Echoes of Life, the science and the politics of research, as well as the collaborations and rivalries of researchers, are carefully portrayed. For example, the chapter “From the Moon to Mars” recounts how researchers receiving bits of the moon from NASA's Project Apollo—and there were many of them—had to swear to secrecy about their results until 5 January 1970 (the first day of a NASA-convened Lunar Science Conference). The book also discusses the interest of oil companies and government agencies, in the United States and abroad, in funding biomarker research. Given recent negative social, economic, and political attitudes toward fossil fuels and oil companies, readers will be fascinated by the historical context of oil research and the quest for the origins of organic matter.

Coauthor Eglinton's observations span five decades, and his work is prominently featured throughout the text. (The preface notes that he had wanted to write a biomarker book for years, so this volume is in part his scientific memoir.) He collaborated with Rullkötter on several projects, and the combination of their scientific perspectives with Gaines's fluid writing makes for an unconventional text on organic geochemistry. The book examines “what molecules (aka biomarkers) know, and what they have to say,” as well as how that knowledge came to exist. It has textbook appeal to those in a variety of disciplines—geochemistry, microbiology, and evolutionary biology, for example—but because the science is at times difficult, the book is best suited for students with backgrounds in biology or chemistry. Its major asset is its exploration of the importance of biomarkers to a range of applications, including detecting ancient life forms and signs of extraterrestrial life, reconstructing ancient climates, and studying microbial evolution. Students will learn about the major researchers in geochemistry, their compounds of interest, and the “big picture” regarding their findings, all described in writing that is as vivid as that in a fine novel.

Another of the book's assets is the quality of the illustrations. Deciphering geochemistry jargon can be difficult, even for those with a background in chemistry. Echoes of Life incorporates diagrams that explain the concepts in a way that will appeal to a variety of audiences. Graphics from several seminal papers are incorporated and blended with original diagrams to illustrate, among other things, how samples are analyzed (including the use of gas chromatography and mass spectrometry), how the science of biomarker research has changed over the decades, and how the findings have improved our understanding of the origins of organic matter, climate change, and evolution. As a bonus, Geoffrey Eglinton's cartoon musings on all aspects of geochemistry are featured throughout the bibliography.

The first few chapters introduce biomarkers and concentrate on Eglinton's studies as a graduate student and postdoctoral researcher with Melvin Calvin. Calvin had received some of Earth's oldest sedimentary rocks and needed them to be analyzed; Eglinton proved to be an eager colleague. Readers will be drawn in by the description of Calvin and Eglinton's enthusiasm as they study Precambrian exudates and slowly figure out what compounds chromatograph and spectrometer peaks represent, and they will keep reading to discover, or rediscover, some of the primary literature cited throughout the text. For example, the Science article (Eglinton et al. 1964) on the identification of hydrocarbons from the Nonesuch shale, a classic that demonstrates the nascence of biomarker research at that time, merits reconsideration. One admires the researchers' ingenuity as they propose and work through connections between pristine and phytane compounds and the digenesis of organic matter in oil.

The importance of analytical instruments and technological innovation in the identification of key biological compounds will not be lost on anyone who has had private conversations with a gas chromatograph or mass spectrometer.

Subsequent chapters highlight how biomarkers have grown in importance to different fields and enhanced the synergies between disciplines. For example, microbes are prominently featured throughout the text. Because of their small size, ancient bacteria and other microbes are not usually found as intact fossils. The chemical remnants of bacterial cell walls and exudates are proving to be strong signatures of the former presence of microorganisms. Coupling this information with molecular analyses, researchers have been able to hypothesize the structure as well as the function of microbial communities.

Biomarker research has also prospered from advances in technology, which in many cases occurred as a result of a particular researcher's desire to isolate one compound. The importance of analytical instruments and technological innovation in the identification of key biological compounds will not be lost on anyone who has had private conversations with a gas chromatograph or mass spectrometer. When they reach the end of the book, readers are likely to have a strong appreciation for the importance of biomarkers, and, like the authors, an optimistic outlook for the science.

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The chapter titles are enticing—for example, “From Moon to Mars,” “Deep Sea Mud: Biomarker Clues to Climate History,” “Microbiologists (Finally) Climb on Board,” “Weird Molecules,” and “Unlikely Environmental Proxies: Marine Ecology Revisited.” “From Moon to Mars” highlights not only the importance of the Apollo 11 mission in the 1960s for moving science forward but also the importance of peer review of claims about the types and origins of organic matter in meteorites and the implications for extraterrestrial life.

To further the current climate debate, the chapter “Deep Sea Mud” explains how compounds such as alkenones, left by the marine alga Emiliania huxleyi, among other species, provide a temperature proxy. These compounds allow researchers to investigate differences in temperature in different oceanic regions, and, together with radiometric dating of sediments, allow temperature histories to be constructed. The last few chapters cover everything from evolution to the novel use of biomarkers in anthropological studies; the final one features thoughts about the future of the science.

Those who are interested in geochemistry, and those who are looking to broaden their knowledge of the connections between chemical compounds and the diversity of life, will find Echoes of Life well worth reading. Readers will come away with an understanding of what those compounds mean in a given time and place. Although the science Gaines and her coauthors present is sometimes difficult, the book nicely blends chemical structures with the researchers behind the discoveries.

References cited

1.

G Eglinton, PM Scott, T Belsky, AL Burlingame, M Calvin. 1964. Hydrocarbons of biological origin from a one-billion-year old sediment. Science 145: 263–264. Google Scholar

2.

SM Gaines. 2001. Carbon Dreams. Creative Arts Book Company. Google Scholar
Karen Bushaw-Newton "Echoes of Life: What Fossil Molecules Reveal about Earth History," BioScience 59(8), 710-712, (1 September 2009). https://doi.org/10.1525/bio.2009.59.8.16
Published: 1 September 2009
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