Eglinton Geoffrey - Echoes of life: what fossil molecules reveal about earth history

Echoes of Life

Susan M. Gaines
Geoffrey Eglinton
Jrgen Rullktter

scientific illustrations by Florian Rommerskirchen

What Fossil Molecules Reveal about Earth History

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Library of Congress Cataloging-in-Publication Data
Gaines, Susan M.
Echoes of life : what fossil molecules reveal about earth
history / Susan M. Gaines, Geoffrey Eglinton and Jurgen Rullkotter ;
scientific illustrations by Florian Rommerskirchen.
p. cm.
Includes bibliographical references and index.
ISBN 978-0-19-517619-3
1. Biomolecules, Fossil. I. Eglinton, G. (Geoffrey) II. Rullktter, J. III. Title.
QP517.F66.G35 2008
572'.33dc22 2008019905

9 8 7 6 5 4 3 2 1

Printed in the United States of America
on acid-free paper

in memoriam

Guy Ourisson

March 26, 1926November 3, 2006

Fossil Molecules in Geologic Time

It is in the atmosphere of [the First World War] that
I have approached a conception of nature, at that
time forgotten and thus new for myself and for
others, a geochemical and biogeochemical
conception embracing both nonliving and living
nature from the same point of view.
Vladimir Ivanovich Vernadsky, 18631945, Russian mineralogist
From American Scientist 33 (1945)

An organic solvent extract of a bituminous oil
shale showed a magnificent red color and the
characteristic absorption spectrum of the metal
complexes of pyrrole pigments. The apparent
preservation of complicated pigment materials
through geological eras raises hopes that the same
may also be true of other types of molecules.
Alfred Treibs, 18991983, German chemist
From Angewandte Chemie 49 (1936)

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 Vernadskys 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 scientistsonce a small scattering of mavericks defying the dictates of their disciplines, now a large, thriving scientific communitywho 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 ones 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 scienceschemical, geological, and biologicalas 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 books 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 Geoffs own laboratory in Bristolbut it was set in California, and Geoff had never heard of the author. Susan Gaines, Meixun told him, was a graduate school friend he hadnt seen in ten years. Recently, shed turned up as a guest speaker at Dartmouth, invited by a geology professor whod 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 theyd 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. Hed drafted an outline for a sort of biomarker casebook based on his and Meixuns lectures. But when he read