One of the greatest mysteries in reconstructing the history of life on Earth has been the apparent absence of fossils dating back more than 550 million years. We have long known that fossils of sophisticated marine life-forms existed at the dawn of the Cambrian Period, but until recently scientists had found no traces of Precambrian fossils. The quest to find such traces began in earnest in the mid-1960s and culminated in one dramatic moment in 1993 when William Schopf identified fossilized microorganisms three and a half billion years old. This startling find opened up a vast period of time – some eighty-five percent of Earth's history – to new research and new ideas about life's beginnings. In Cradle of Life, William Schopf, a pioneer of modern paleobiology, tells for the first time the exciting and fascinating story of the origins and earliest evolution of life and how that story has been unearthed.
Gracefully blending his personal story of discovery with the basics needed to understand the astonishing science he describes, Schopf has produced an introduction to paleobiology for the interested reader as well as a primer for beginning students in the field. He considers such questions as how did primitive bacteria, pond scum, evolve into the complex life-forms found at the beginning of the Cambrian Period? How do scientists identify ancient microbes and what do these tiny creatures tell us about the environment of the early Earth? (And, in a related chapter, Schopf discusses his role in the controversy that swirls around recent claims of fossils in the famed meteorite from Mars.) Like all great teachers, Schopf teaches the non-specialist enough about his subject along the way that we can easily follow his descriptions of the geology, biology, and chemistry behind these discoveries. Anyone interested in the intriguing questions of the origins of life on Earth and how those origins have been discovered will find this story the best place to start.
Prologue xi
Acknowledgments xv
Chapter 1. Darwin's Dilemma 3
Breakthrough to the Ancient Past 3
The Nature of Geologic Time 4
The "Schoolbook" History of Life 10
Darwin's Dilemma 13
Denouement 34
Chapter 2. Birth of a New Field of Science 35
The Floodgates Crack Open 35
Famous Figures Enter the Field 48
A Youngster Joins the Fray 52
The Floodgates Open Full Bore 61
Chapter 3. The Oldest Fossils and What They Mean 71
"Trust but Verify" 71
"Real World Problems" in the Search for Early Life 71
Questions and Answers about the Oldest Records of Life 75
The Oldest Fossils Known 99
Chapter 4. How Did Life Begin? 101
The Basics of Biology 101
The Universals of Life 107
How Did Monomers of CHON Arise on the Lifeless Earth? 108
Organic Monomers beyond the Earth 131
How Did Monomers Become Linked into Polymers? 134
From Monomers to Polymers toward Life 138
Chapter 5. Metabolic Memories of the Earliest Cells 139
How Did Cells Begin? 139
The Essentials of Life 143
Life's Earliest Way to Make a Living 150
Air and Light: A New Source of Glucose 155
Why Do We Breathe Oxygen? 158
The Four-Stage Development of Modern Metabolism 161
Chapter 6. So Far, So Fast, So Early? 164
How Old Is the Modern Ecosystem? 164
When Did Life Begin? 166
How Did Evolution Proceed So Far, So Fast, So Early? 168
Paleobiology: Fossils, Geology, and Geochemistry 169
Isotopic Evidence of Ancient Metabolisms 173
Paleobiology: Direct Evidence of Early Evolution 181
Chapter 7. Stromatolites: Earth's First High-Rise Condos 183
Nature Is Not Compartmentalized 183
Stromatolites: Earth's First High-Rise Condos 184
Stromatolites of the Geologic Past 195
What Are Stromatolites Good For? 201
Chapter 8. Cyanobacteria: Earth's Oldest "Living Fossils" 209
Modes and Tempos in the Evolution of Life 209
The Status Quo Evolution of Cyanobacteria 215
Evolution's Most Successful Ecologic Generalists 231
Chapter 9. Cells Like Ours Arise at Last 236
Life Like Us Has Cells Like Ours 236
DNA and Development: Keys to Eukaryotic Success 237
How Old Are the Eukaryotes? 240
Eukaryotes Perfect the Art of Cloning 243
Sex: A New Lifestyle Brings Major Change 246
The Wax and Wane of Precambrian Acritarchs 252
Prelude to the Phanerozoic 259
Chapter 10. Solution to Darwin's Dilemma 264
The Adventure of Science 264
Take-Home Lessons 269
Solution to Darwin's Dilemma 269
EPILOGUE
EXTRAORDINARY CLAIMS!
EXTRAORDINARY EVIDENCE? 279
Chapter 11. Fossils, Foibles, and Frauds 281
The Goal Is to "Get It Right" 281
"Man, a Witness of the Deluge" 282
Beringer's Lying Stones 291
Theories on the Nature of Fossils 299
Unearthing a Rosetta Stone 303
Chapter 12. The Hunt for Life on Mars 304
Hints of Ancient Martian Life? 304
NASA Stages a Press Conference 306
Meteorites from Mars 310
Search for the Smoking Gun 313
Lessons from the Hunt 324
Glossary 327
Further Reading 349
Index of Geologic Units and Genera and Species 357
Subject Index 361
J.William Schopf is Professor of Paleobiology and Director of the Center for the Study of Evolution and the Origin of Life at UCLA. He is a member of the National Academy of Sciences and the American Philosophical Society, President of the International Society for the Study of the Origins of Life, editor of eight volumes, and discoverer of the oldest records of life on Earth
"A book that bears out [Schopf's] assertion that science is enormously good fun!"
– Scientific American
"What were your very earliest ancestors like? I do not mean your great-great-great-grandparents. I mean the earliest life on the planet. In principle we all have a unique lineage of ancestors that runs all the way back to the origin of life. What was life like then – and is the supposed life on Mars our cousin? These are the problems palaeontologist Bill Schopf faces [...] It has been a while since I read a book with so much good sense, put over in so amicable a style. If I ever were to discover my great-great-great grandparents I hope they turn out to be as wise as Schopf."
– Laurence Hurst, New Scientist
"In the well-written Cradle of Life, Schopf tells his own story of how Earth's early microbial biosphere was discovered."
– Stefan Bengtson, Nature
"A very clear introduction to the first living things [...] Schopf [...] adopts an unusually informal first-person style for this rangy exploration of how Pre-cambrian fossils came to light and what they've taught us."
– Publishers Weekly
"An exceptional description of the field that is accessible to any educated lay reader."
– Library Journal (starred review)
"Schopf combines his often entertaining personal story with an introduction to the discipline of paleobiology, with asides on the chemical makeup of life [...] A good introduction to the history of a science on the cutting edge."
– Kirkus Reviews
"A good introduction to a quickly evolving topic [...] Schopf also offers a number of insider nuggets."
– Choice
"Schopf's subject, the origin of life, is fascinating, and as significant as any question that has ever been asked in academia. His explanation of the science behind his conclusions is clear, his approach is well organized [...] This is a marvelous, magnificent, scientific adventure."
– John R. Alden, Cleveland Plain Dealer
"Cradle of Life provides the best current popular overview of the first 85% of life's history on Earth, and that is history worth reading."
– Robert M. Hazen, Physics Today
"An extraordinary account of a monumentally complex subject presented in simple and understandable terms, and in an eminently readable style."
– Steve Voynick, Rock and Gem
"'I am born', writes Dicken's David Copperfield, in simple statement of fact. Our knowledge of how the first cells and organisms were begotten is far less resolute. With focused vision, Cradle of Life probes one view of primordial Earth and the succor of its first cells and organisms, even as scientists explore and assemble evidence to advocate other possibilities. Schopf engages the reader with the magic of storytelling as he writes about such matters as the fables and foibles of scientists, the demands of discovery and documentation in attaining an understanding of how life evolved, the tempo of evolution, and, of course, the continuing saga of the Mars rocks."
– Cindy Lee Van Dover, author of Deep-Ocean Journeys
"An entertaining and informative book. It provides an interesting perspective on how science is done [...] Schopf's personal perspective provides a sense of the personalities involved and engages the reader."
– Dawn Y. Sumner, University of California, Davis