Fifth Miracle: The Exploration of the Origin of Life

Author: Davis
Publisher:
Publishing Time: 2004-01-01
Features: Where does life come from? This is a question that humans have been trying to answer but have never been able to confirm. Since the time of Darwin, there have been only two theories about the origin of life. One is the "warm little pond" theory proposed by Darwin, which suggests that life originated on the Earth's surface through water-mediated self-chemical reactions; the other is panspermia, which posits that life arrived on Earth from space in the form of existing microorganisms. In this book, Paul Davies uses the latest research findings from related disciplines such as molecular biology, biochemistry, and Mars meteorite studies to propose a new theory of the origin of life, namely that life originated from the deep, hot interior of the Earth. At the same time, he powerfully demonstrates the possibility of life spreading between planets through meteorites. This book is well-researched and clearly written, making it an outstanding work of popular science. Preface In August 1996, a message spread around the world: an ancient meteorite may carry evidence of life on Mars. President Clinton personally announced this astonishing news to the public and the scientific community. The significance of this discovery (if it exists) lies in the fact that it was announced by a proper high-ranking leader. This unforgettable event is one of the few instances where scientific achievements have had a direct and major impact on the public. However, the cheers and laughter obscured the true meaning of these discoveries. In recent years, scientists have dramatically revised their thinking about the origin of life. Textbooks say that life began billions of years ago in warm little ponds on the Earth's surface. But increasingly, evidence points to an entirely different and unexpected result. Now, there are signs that the earliest life on Earth lived deep underground, buried in geothermal rocks that resemble a pressure cooker, only later migrating to the surface. Surprisingly, the descendants of these primitive microorganisms still live there, several kilometers beneath our feet. Just a few years ago, no one could believe that life could exist in such a harsh environment. But once people accept that organic matter can be active beneath the surface, another strange possibility begins to emerge. Perhaps microorganisms also lurk in the rocks beneath the Martian surface? The discovery of possible bacterial fossils in Martian rocks is the main evidence for this theory. But that's not all. Scientists soon found an astonishing result. It is highly likely that life actually began on Mars and then followed meteorites to Earth. Enthusiasm surrounded Martian meteorites, and scientists formed different factions based on their interpretations of the evidence. If this evidence is confirmed, it would either mean that life began twice in the solar system or that life spread from one planet to another. But if the latter explanation is correct, then although it is exciting to discover that life can cross from one planet to another, the ultimate origin of life will remain a mystery. But precisely, how did life begin? What physical and chemical processes can transform inorganic matter into organic matter? This is one of the great scientific challenges we face. Currently, a large army of chemists, biologists, astronomers, physicists, and mathematicians is working on finding solutions. Based on their research, many scientists eagerly conclude that the laws of nature are directly arranged for life. They believe that life will form regardless of whether the conditions are right—not only on Mars but also throughout the universe, and even in test tubes. If they are correct, this means: life is part of the natural order of things, and we are not alone. The belief that life is integrated into the laws of nature resonates with some past religious views that the universe was designed for life. Many scientists may dismiss this, insisting that life originated from a unique chemical accident on Earth, resulting in complex organisms, including conscious life, as a result of a massive cosmic gamble. The core of this debate is humanity's place in the universe—who we are and how we should adapt to our place in this grand order. Astronomers believe that the universe formed 100 to 200 billion years ago after a massive explosion. It was born with immense heat energy. In the instant of that explosion, fundamental physical energy and basic particles of matter were created. As the explosion neared its end, the fundamental matter of the universe was formed. Space was filled with subatomic particles—protons, neutrons, and electrons—enveloped in high-temperature radiation at billions of degrees. By today's standards, the universe at that time was featureless. The matter of the universe spread through space in almost the same way. Temperatures were everywhere the same. Matter, heated to extremes, was broken down into the most basic elements, existing in the simplest forms. Even the most imaginative observer would not imagine the immense potential hidden in such a lifeless state. No evidence suggests that billions of years later, trillions of hot stars would organize themselves into countless spiral galaxies, where planets, crystals, clouds, and oceans, mountains and glaciers would exist; where trees, bacteria, elephants, and fish would live, and where the laughter of humans would echo. And all of this is unpredictable. As the universe expanded from its original state, it gradually cooled. Lower temperatures brought more possibilities. Matter would gather to form huge amorphous structures—today's seeds of galaxies. Atoms began to form, paving the way for the formation of solid natural objects. From this point on, many emerged in the universe: giant black holes, with masses equivalent to billions of suns, devouring stars and erupting with gas; neutrons spinning at a rate of a thousand times per second, their matter colliding and producing 10 billion tons of debris per cubic centimeter; subatomic particles so elusive that they can penetrate solid lead several light-years thick; terrible gravitational tides, whose brief stays left almost no trace. Yet, despite the wonder of these phenomena, the phenomenon of life is more revolutionary than all of them. It did not bring any sudden or dramatic change to cosmic phenomena. In fact, if life on Earth is just a fleeting guest, the changes it brought would be very slow. However, once life formed, this universe would be fundamentally different. It would slowly but surely change the planet Earth. By providing consciousness, intelligence, and technological means, it has the potential to change the universe. This book is about the origin of life, or abiogenesis. I want to state at the beginning that this topic is not my professional field. I am trained as a theoretical physicist. However, I have a deep interest in abiogenesis and related questions, such as whether we are alone in the universe. My interest in these questions dates back to the 1960s, when I studied physics at University College London as a student. Like many of my friends, I read Fred Hoyle's famous science fiction novel "The Black Cloud," which primarily describes a massive atmospheric cloud from interstellar space entering the solar system. Such clouds are well known to astronomers, but Hoyle's was to assume that these clouds were alive. Now, this is a puzzle. How can a cloud be alive? I became very confused. Atmospheric clouds are merely following physical laws? How can they exhibit autonomous activity, think, and make choices? But at that time, to me, all living organic matter followed physical laws. Hoyle's greatness lay in using the example of a cloud to outline a seemingly paradoxical argument. "The Black Cloud" left me confused and bewildered. I wanted to know exactly what life is and how it came to be. Perhaps something interesting happens within living organic matter? At that moment, my doctoral advisor (as a form of relaxation exercise) gave me a wonderful article by the respected physicist Eugene Wigner. The article aimed to prove that under the premise of not violating the laws of quantum physics, physical laws could not complete the transition from inorganic to organic states. Ah-ha! So, Wigner at least believed that when life began, something interesting must have happened. Soon after, my advisor gave me an article on biology by the astrophysicist Brandon Carter. The article raised an important and interesting question about life that could not be avoided: What is life, and how did it begin? Carter posed the question: What features must the natural universe have to allow life to exist? Suppose by magic, you could change the natural laws or the initial conditions of the Big Bang. To what extent could you change the fundamental laws or structure of the universe while still allowing life to exist? For example, as we know, life requires certain chemical elements, especially carbon. But during the Big Bang, almost no carbon atoms were produced; most carbon atoms were produced inside stars. Fred Hoyle had long noticed that the successful production of carbon inside stars was actually very dangerous, it was subtly dependent on the properties of nuclear energy. If you handle it with the basic laws of nuclear physics, the universe would produce only a small amount of carbon, or none at all, and there would be no life. Carter's view became known as the famous "anthropic principle." He even boldly argued that the existence of life was highly uncertain, a result of some coincidence in the potential mathematical structure of the universe. Although Carter's article was thought-provoking, it still left the secret of life unexplained. Shortly after reading the article, I found a research position at the Cambridge Institute of Theoretical Astronomy, where Fred Hoyle was the director and Brandon Carter was a researcher. During that time, I happened to come across a pamphlet by the physicist Erwin Schr?dinger, which seemed to address the very problems I was concerned with. The title of the book was "What is Life?" and it mainly explained why, from a physics perspective, living organic bodies were so mysterious. I later found that the book had influenced the field of molecular biology for the next two decades. Unfortunately, Schr?dinger's book raised more questions for me than it answered, and I had to put the question of abiogenesis in the "too difficult" corner of my mind. However, Carter gave me a revised version of his article on the anthropic principle (which was never published). Together with another researcher at the institute, Bill Sutherland, we began to study Carter's views. We even tried to meet Francis Crick, who was working at the Laboratory of the Cambridge Medical Research Society at the time. But Crick was too busy, and Carter seemed to have a tight control over the topic of the anthropic principle, so my interest in biology began to wane. My interest was reignited many years later, in the early 1980s. Martin Rees (now Sir Martin Rees, Astronomer Royal) helped organize a forum at Cambridge called "From Matter to Life." Rees, along with Bernard Carr, another astronomer, published a famous article in the journal "Nature" in 1979, which revitalized the topic of the anthropic principle. The forum attracted many physicists and astronomers, such as Brandon Carter, Freeman Dyson, and Tom Gold, biologists like Lewis Wolpert and Heinz Bremer, mathematicians like John Corvino, and abiogenesis advocates like Manfred Eigen and Graham K. Smith. The main topic of the forum focused on how life began, but no final conclusions were reached, only key scientific and conceptual questions were raised. I began to rethink the mystery of life. Over the past few decades, I have found that I was again influenced by Hoyle, Dyson, and Gold's views. Hoyle, in collaboration with Chandler Wittelsinger, boldly proposed that perhaps life did not originate on Earth but was brought to Earth by comets. Dyson similarly boldly speculated on the origin of life, letting his imagination run wild and imagining the future and ultimate fate of technological civilizations. Gold believed that vast amounts of hydrocarbons were buried underground, and when his hypothesis was investigated, new forms of underground life were discovered. All these developments helped shape my views on this topic. Another person who deeply influenced my interest in abiogenesis was Keith N?rreklit, a colleague of mine at Newcastle University. N?rreklit was a geophysicist whose research interests ranged from the Earth to the solar system. Although geophysics far exceeds my own field of expertise, I often attended his seminars and forums. The 50th Meteoritical Society Symposium held in Newcastle in 1987 is considered a landmark event, and my initial understanding of Mars meteorites began there. The fragments that followed appeared in the early 1990s, when I was working at the University of Adelaide in Australia. There, I became interested in the work of Duncan Steele, an expert in collisions between asteroids, comets, and planets. It was Steele who introduced me to the fact that matter could be blasted out of planets by cosmic collisions, an idea that formed the basis of my theory that microorganisms traveled from Mars to Earth. When I began writing this book, I was firmly convinced that science was about to strip away the mystery of the origin of life. The striking evidence of microorganisms living underground might provide the missing link between the biochemical mixture world before life and the first primitive cells. However, the fact is that many scientists working in this field confidently believe that most of the mysteries of abiogenesis have already been solved. Recent books have conveyed the message that the origin of life is not as mysterious as it seems. But I believe they are wrong. After studying this field for one to two years, I now believe that there is a huge gap in our understanding. It is certain that we have a good understanding of when and where life began, but we still have a long way to go in understanding how life began. This understanding gap is not just a matter of neglecting certain technical details; it is a major conceptual gap. I am not suggesting that the origin of life is supernatural, but rather that we have lost some very fundamental aspects of the process. If this is the case, as many experts and critics believe, that life will arise as long as the conditions are right, then indeed, some very interesting things have happened in the universe, some profound philosophical changes. My personal view is that a complete and satisfying theory of the origin of life needs some fundamentally new perspectives. For many researchers, it is considered embarrassing to publicly state that the origin of life is a mystery, although privately, they all frankly admit that they are indeed confused. The reason for this discomfort seems to be two-fold. First, they feel that this undoubtedly opens the door to religious fundamentalists and their "fill-in-the-blank" God. Second, they worry that frankly admitting their ignorance will lead to the reduction of research funding, especially for the study of extraterrestrial life. Because some believe that as soon as scientists confirm that life exists elsewhere in the universe, governments will invest in the search for cosmic life. I believe this attitude is completely misguided. Scientists are not exaggerating the need for it just for the sake of public consumption. What is more, ignorance provides better motivation for experimentation. It is very important to search for life on other worlds and then test the synthesis of life in the laboratory, because we have no certainty about how life came to be. If my view is correct, that abiogenesis implies something fundamentally new and surprising, then the study of other worlds might actually capture this apparent change in practice. Astronomers believe that the outer planets like Saturn and Jupiter, along with their moons, are vast pre-life laboratories where the steps toward Earth life were temporarily halted, caught between the complex chemical world and the real biological world. As for Mars, the line between life and non-life seems to have crossed at some point in the past, and life on the red planet was once so active. In fact, given many of the reasons I will explain in this book, I believe that life did indeed exist on Mars in the past. I also believe that it is entirely possible to find life on Mars today if you know where to look. Solving the mystery of abiogenesis is not just one long list of scientific tasks that need to be completed. Like the origin of the universe and the origin of consciousness, it is a symbol of something deeper, because it tests the foundations of our scientific and worldview foundations. A discovery that promises to change the principles by which we understand the material world is worth. For two and a half centuries, the mystery of the origin of life has puzzled philosophers, theologians, and scientists. In the coming era, we will have a golden opportunity to make major breakthroughs in this field. The fact that scientists are currently struggling in this field makes this opportunity even more exciting and noteworthy. I believe that without a deep understanding of the nature of life, the question of the origin of life cannot be solved. What is life? The characteristics of life are so unique that it is described as a state of variability. In this book, I begin with the famous puzzle of defining life. Most textbooks focus on the chemistry of life: the role of molecules in cells. It is clear that life is a chemical phenomenon, but the difference is that it is not just a chemical phenomenon. The secret of life lies in its informational features; a living organism is a complex information-processing system. Complexity and information issues belong to the field of thermodynamics, which is a branch connecting physics, chemistry, and computational science. For decades, there has been a suspicion that life is so remarkable that it must somehow involve thermodynamic principles. Especially, the second law of thermodynamics—the most fundamental principle in nature—describes life's apparent resistance to decay and decline. I explore the second law of thermodynamics extensively in Chapter 2, because it provides the context for what I believe is the ultimate question of abiogenesis: the origin of biological information. Regardless of what happened on the primordial Earth or on other planets, the dawn of life was not brought about by the immense power of molecules but, to some extent, by the combination of information. This view is further elaborated in Chapters 3, 4, and 5. In those chapters, I describe various competing theories of primordial mixtures that turn chemistry into life, as well as other ideas, and I describe efforts to create life in the laboratory; I also give a brief overview of the fossil evidence for the earliest life forms. Some introductions to Darwinism and basic molecular biology may be familiar to the reader and can be skipped. However, I always try to give new interpretations to traditional views. If I am correct, that the key to abiogenesis is not chemistry but the formation of a specific logic and information structure, then the key step involves the creation of an information-processing system, including software control. In Chapter 4, I argue that this key step is closely linked to the emergence of genetic coding. I introduce computational language and concepts into the problem, trying to unravel new forms of complexity found in the genes of living organisms. The characteristics of biological complexes make the genome seem like an impossible object—but it must have formed. I finally conclude that no familiar natural law (as some scientists claim) can produce such structures from unordered chemicals. If life formed easily and is widespread in the universe, then new physical principles must be at work. This is the theme of the final chapter, where I try to explain how if the universe is filled with life, it will lead to profound philosophical changes—because many seem to believe this. I do not doubt that the origin of life is not a miracle, but I believe more that we live in a highly creative and life-friendly universe. The latter half of this book is mainly dedicated to proposing a truly new theory of the origin of life. Since the time of Darwin, there have been only two theories of abiogenesis. One is that life originated on the Earth's surface through water-mediated self-chemical reactions—Darwin himself described it as a "warm little pond." The other is the theory of panspermia, which posits that life arrived on Earth in the form of existing microorganisms from space. In the latter scenario, the ultimate origin of life is a mystery. However, in recent years, increasing evidence has led me to believe there is a third option: life originated inside the Earth. Not very deep inside, but several kilometers beneath the hard crust, perhaps under the seabed, where geothermal activity creates an environment similar to a giant boiler. The extreme heat and energy beneath the surface, especially near volcanic vents, constantly kill most known organisms. Yet, such environments are ideal for biochemical synthesis, and scientists have found that strange microorganisms still live there, with temperatures far above the boiling point of water. I describe these superbugs in Chapter 7, and I firmly believe they are living fossils left over from the dawn of life. I have reasons to believe (which I explain in Chapter 8) that the same superbugs that lived beneath the Martian surface could still survive today, deep underground on Mars. I further believe that these microbial organisms have traveled between Earth and Mars on rocks (these rocks were blasted out of the planets during large meteorite impacts). A significant portion of Chapter 8 is devoted to describing the controversial Martian meteorites, especially the famous ALH84001, which NASA scientists called a fossil containing Martian microorganisms. Almost certainly, interplanetary destruction (which seems to be largely ignored in recent debates about life on Mars) raises questions about the ultimate origin of life. Did life originate on Earth, Mars, or both? Or did it come from some other planet? In Chapter 6, I explore the importance of astronomy for abiogenesis, and in Chapter 9, I review the evidence for the revived panspermia theory. During the preparation of this book, I benefited greatly from in-depth discussions with many outstanding colleagues. Some I have mentioned. Here, I would like to express my special thanks to: Susan Barnes, Robert Hanford, John Parks, Steven Ross McCraskey, Duncan Steele, and Malcolm Walter, who all read my early drafts and gave valuable advice. Other individuals who gave me very valuable help during the writing process include: Diane Edy, David Blair, Juliet Brown, Roger Baker, Juliet Chelley-Flores, George Coy, Helene Cronin, Robert Croty, Susan Davies, Reza Ghatil, Monica Greedy, Gary Joyce, Stuart Kauffman, Bernd Olfert Cooper, Clifford Matthews, Chris Mcale, Jay Melosh, Curt Mokoski, Martin Redford, Martin Rees, Everett Schack, Lee Smolin, Roger Somers, Rudiger Vans, Francis Westall, and Ian Wright. Similarly, I would like to thank Fran Okon for his help in preparing the index. Finally, I would like to say a few words about the title of this book. It comes from the description in the Book of Genesis, which describes how God created the world through a series of specific steps. The eleventh verse says, "Let the land produce vegetation." This is the first mention of life, and it seems to be the fifth miracle. The first four miracles are: the birth of the universe, the birth of light, the birth of space, and the birth of dry land. Biblical scholars tell me that this enumeration is a misinterpretation of the Book of Genesis, because its opening "God created the heavens and the earth in the beginning" is not a description of a miraculous act but an explanation of the entire process that follows. However, I still insist that it is the fifth miracle. When using this title, I am not trying to say that the origin of life is actually a miracle. I suggest that readers interested in the theological implications of the title can refer to my earlier works, "The Mind of God" and "Are We Alone?" Paul Davies, Adelaide, South Australia