Seventy years ago, a German chemist identified certain organic molecules, 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. Outspoken against the Nazi regime, Alfred Treibs lost his university post and standing not long after this discovery. Though he proposed that other types of molecules might have left similarly recognizable traces, it would be another 25 years before his insight would be developed and the term “biomarker” coined to describe fossil molecules whose atomic makeup and molecular structures could reveal the activities, both past and present, of otherwise elusive organisms and processes. Over the past 50 years, hundreds of biomarkers have been identified in oceans and sediments, ancient rocks and oils, soils and coals, and in individual fossils. They are helping paleoceanographers to elucidate the temperatures and carbon dioxide concentrations of ancient seas, and climatologists to predict those of future ones; petroleum geologists to predict the whereabouts of oil; evolutionary biologists to understand cell evolution; paleontologists to determine when flowering plants evolved; microbiologists to understand the ecology of microbes in natural waters and sediments…. Biomarkers have provided evidence for Vladimir Vernadsky’s prescient stipulation that the biosphere was inseparably linked to the geosphere and had been so since its inception. They are providing clues to some of the earliest forms of life on the earth, and as space exploration makes extraterrestrial rock samples available, biomarker analyses may help in detecting past or present life elsewhere in the solar system. Echoes of Life is the story of these molecules and how they elucidate the history of the earth. It is also the story of the scientists—once a small scattering of mavericks defying the dictates of their disciplines, now a large, thriving scientific community—who have learned to detect, measure, and interpret the molecular clues.
This is a book to be read for pleasure and contemplation as well as information and education, lying on a couch or sitting at a desk, depending on one’s inclination. It is an attempt to unite 50 years of research, scattered across half a dozen disciplines and at least as many countries, into one scientifically and historically coherent treatise. Students and practitioners of organic geochemistry will, we hope, enjoy and learn from the panoramic view of their discipline and the history of its development, just as we have. Geologists, biologists, microbiologists, and oceanographers will gain a deeper understanding of and appreciation for the insights provided by organic chemistry. The extent to which molecular structure and function can reveal the history of the earth and evolution of biochemical systems will be a revelation for many organic chemists and biochemists and, we hope, an inspiration for their students. Indeed, undergraduate students and non-academic readers may find that Echoes of Life offers them a rigorous but exciting entrance into the natural sciences—chemical, geological, and biological—as well as an appreciation for science as a living, breathing beast that grows and develops, errs and triumphs. The book is based on a simple premise, all too often forgotten in the scientific literature but a banal fact of life for any working scientist: science is a narrative, a perpetually unfolding story, and despite its definitive rules of objectivity, human characters are integral to every scientific plot. With that in mind, the story of this book’s genesis may be instructional.
In 2001, Meixun Zhao, then a professor at Dartmouth College in New Hampshire, told his British colleague and longtime collaborator Geoff Eglinton about an unusual novel. It included biomarker research among its main themes and told a story of discovery that was eerily reminiscent of one that had taken place in Geoff’s own laboratory in Bristol—but it was set in California, and Geoff had never heard of the author. Susan Gaines, Meixun told him, was a graduate school friend he hadn’t seen in ten years. Recently, she’d turned up as a guest speaker at Dartmouth, invited by a geology professor who’d been intrigued by her literary rendition of geochemistry. Perhaps, Meixun suggested, she could write the biomarker text that he and Geoff had been mulling over, something that could be used in courses for undergraduates like the one they’d been teaching together at Dartmouth. Geoff, Professor Emeritus at Bristol, was then on the adjunct faculties at both the Woods Hole Oceanographic Institution and Dartmouth. He’d drafted an outline for a sort of “biomarker casebook” based on his and Meixun’s lectures. But when he read Carbon Dreams he started dreaming of something more ambitious: a popular science book about biomarkers that would bring the process of doing scientific research to life the way the novel had, replete with all its warts, tedium, beauty, and excitement.
When Geoff contacted me about writing a biomarker book, I was in California, deeply immersed in work on another novel. He invited me out to Woods Hole to give a presentation from Carbon Dreams and discuss his book idea. I’d read many of his papers while working on the novel and was intrigued and flattered by the invitation. I was genuinely fascinated by the biomarker work, I told him, but I’d given up science a decade ago and committed myself to writing fiction. The sort of literary fiction I was attracted to had little commercial appeal, so the rest of my time was consumed by freelance editing and teaching. And to be honest, I didn’t generally like popular science books. I found them somehow frustrating, the science too facile and watered down to be interesting. Thinking that was the end of it, I went back to California, and then headed south to Uruguay, where my novel-in-progress was set.
Meanwhile, Carbon Dreams was making the rounds in the scientific community. Jürgen Rullkötter at the University of Oldenburg in northern Germany was charmed by the unusual book, which his friend Keith Kvenvolden from the U.S. Geological Survey in California had sent him as a gift. Here was a mix of science and literature that he had never seen before! He would nominate the author as the “art-in-science” fellow at the nearby Hanse Institute for Advanced Study, which hosted scholars and scientists from around the world and was experimenting with an occasional creative artist. She could write another of these science novels, and it would be great fun!
Geoff, who had been one of the Hanse Institute’s first fellows, had a similar idea—except that he was still thinking about his biomarker book. I’d told him, somewhat tongue-in-cheek, that if the book paid all my bills and subsidized writing a novel I might be interested, and he’d taken this as a green light to find funding and support for the project. All that was needed to nominate me for a Hanse fellowship was a collaborator at the University of Oldenburg or Bremen who was similarly inspired, and it so happened that he and Jürgen were working on a paper together. . . .
So this is how the three authors of Echoes of Life came together: an organic geochemist in Oldenburg, a founding father of the biomarker concept from Bristol, and a marine chemist cum novelist who suddenly found herself commuting between California, Montevideo, and someplace called Delmenhorst in northwestern Germany. Out of the blue, when I had long forgotten about Geoff’s curious proposition, I received an e-mail from a stranger named Jürgen Rullkötter, who said he had enjoyed reading Carbon Dreams and wondered if I would be interested in a fellowship at an Institute for Advanced Study in Germany. He said he had been talking to Geoff Eglinton about the possibility of me writing a book about biomarkers. Only now, after four years of intense immersion in the science I once abandoned, as we prepare this manuscript for publication, do I learn that Jürgen’s first impulse had been to offer a Hanse fellowship for writing a novel—which would have been like manna from heaven for this writer. As it was, the manna was something less than heavenly, but still pretty sweet. All I had to do was spend 10 months over the next two years in Delmenhorst, wherever that was, give one talk, and start work on a book about biomarkers. I said yes. . . . But what sort of book?
Not a popular science book, with an entertaining story and watered-down science. Not a dry textbook, with its efficient presentation of accumulated, finely honed knowledge. Rather, a narrative science book. We would present the science in the same way it was produced, as the product of rampant human curiosity that had been systematically indulged and constrained by the rules of the scientific method. We would make the book accessible, entertaining, and rigorous. Like its subject, Echoes of Life is geared to a wide spectrum of readers, but some minimal education in the sciences—an introductory course in organic chemistry, biology, or geology at some point in one’s past—is probably prerequisite. We employ a loosely historical structure, divided by the ever-expanding applications of the biomarker concept in petroleum exploration, space sciences, oceanographic and climate studies, microbiology, and so on. Chemical descriptions often elude those not trained in the language of chemistry, but our historical narrative moves naturally from the simple to the more complex, and the chemistry is presented in the context of its applications: readers not versed in organic chemistry can absorb its language and basic premises while reading about the earth’s changing climates or the first signs of life in its rocks, and no one has to wade through a tedious exposé on chemical nomenclature. All but the most general scientific terms are defined at first mention, and there is an extensive glossary at the end of the book. Figures and illustrations are fully integrated into the text, but readers can relocate them easily by referring to the list of figures at the end of the book. Those with a limited background in geology may find the opening figure (“Fossil Molecules in Geologic Time”) useful for reference, and the appendix (“Biomarkers at a Glance”) and closing figure (“A Biomarker-centric Tree of Life”) provide a quick overview and reminder of molecular structures, names, sources, and biomarker uses.
I have pieced our story together from thousands of scientific papers and from researchers’ memories of the evolution of their thinking. A few disclaimers are in order. We have strived for the utmost rigor in our presentation of organic geochemistry, with some minor compromises for accessibility and the narrative style. The many associated fields of science that we discuss are, of necessity, treated more superficially, and our cumulative expertise is more limited: we are likely to incur the wrath of specialists, though we have made every attempt at accuracy. The book’s historical narrative is, however, openly and unabashedly anecdotal, used mostly as a vehicle for exploring the science. Certainly the interests and personal experience of the three of us have flavored the account. With one of the founding fathers of biomarker research—onetime Ph.D. or postdoctoral adviser to many of its current practitioners—as coauthor, it was only natural to begin with his story and perspective. I also engaged many of the book’s main characters in long interviews and conversations, and their ideas and memories inform its narrative. I sought out many of them, but there is also a circumstantial component to these conversations, as whom I talked to depended to some extent on who happened through northern Germany while we were working on the book. For a more definitive outline of the history of organic geochemistry, we recommend two articles in the 2002 volume of Organic Geochemistry, Keith Kvenvolden’s “History of the Recognition of Organic Geochemistry in Geoscience” (pp. 517–521) and J. Hunt, R. P. Philp, and Kvenvolden’s “Early Developments in Petroleum Geochemistry” (pp. 1025–1052).
In the interest of readability, clarity, and literary aesthetics, we have resisted the temptation to cite every author of every work discussed and generally named only central “characters,” often the leaders of dedicated biomarker laboratories or researchers whose work comes up repeatedly throughout the book. With the exception of a few key historical figures, we generally discuss work in peripheral fields without assigning credit. This leaves many coworkers, younger researchers, and students unacknowledged, even though they may have done the bulk of the work on a given project. We beg their pardon, but hope they will take some comfort in knowing their science has been integrated into a larger, cohesive panorama and their personal citations subordinated to the cause. We are confident that the chapter bibliographies at the end of the book will lead readers to their work and names. The bibliographies are selective, comprising only a fraction of the papers that inform the text, but these include representative papers from the recent literature and review papers with full reference lists from the older literature.
Echoes of Life is a somewhat unorthodox science book. For a more straightforward textbook on organic geochemistry, we recommend S. Killops and V. Killops’s Introduction to Organic Geochemistry (2005). For an encyclopedic reference book on biomarkers and their many applications, we recommend the two-volume The Biomarker Guide (2005), by K. E. Peters, C. C. Walters, and J. M. Moldowan.