Four billion years ago, the infant Earth was a seething cauldron of erupting volcanoes, raining meteors, and hot noxious gases, totally devoid of life. But a relatively short time later - only 100 million to 200 million years - the planet was teeming with primitive organisms. What happened? Now you can find out - in a series of 24 vibrant lectures from a leader of the NASA - supported team studying the origins of life in the universe and also one of the nation's foremost science educators. The lectures take you from path-breaking experiments in the 19th century that proved the molecules of life to be no different from other chemicals, to our increasingly sophisticated modern understanding of just how the chemistry of life works, to the near certainty that the 21st century will see spectacular and unpredictable developments in our understanding of how life began. For all its familiarity, life is an elusive concept that is hard to define, much less explain. These lectures show how scientists are systematically building a picture of the process by which those chemical reactions on the early Earth eventually led to the first appearance of the DNA-protein world that remains the fundamental basis of all life today. And you'll join them as they probe for evidence of life beyond our planet. Crammed with fascinating experiments, surprising results, heated debates, blind alleys, and promising leads, the investigation of life's origins is a mystery story in the truest sense - one in which the clues are slowly adding up but the solution is not yet in hand.
Origins of Life
Discover how scientists are systematically building a picture of the process by which chemical reactions on the early Earth eventually led to the first appearance of the DNA-protein world that remains the fundamental basis of all life today.
01: The Grand Question of Life’s Origins
Professor Robert M. Hazen introduces the mystery of life's origins and outlines three reasons why this is "not your usual science course:" (1) the answer to the problem is not yet known; (2) the course emphasizes the "process" of science; (3) the search for life's origins is controversial in a way that other scientific studies are not.
02: The Historical Setting of Origins Research
This lecture reviews the history of origins research and shows how early efforts to answer this question were hampered by the "absence" of: relevant evidence, appropriate experimental equipment, and a theoretical understanding of emergence (the spontaneous origin of complexity out of simple systems).
03: What Is Life?
Life probably arose as a sequence of steps. First came the synthesis of simple organic molecules. Next came the assembly of macromolecules. Eventually, an evolving, self-replicating collection of macromolecules emerged. Each of these stages added some degree of chemical and structural complexity.
04: Is There Life on Mars?
You survey the quest for life on Mars from the telescopic era to the space age. While studies by spacecraft on Mars have given ambiguous results, another source of data is from meteorites that are known to have come from Mars; one of these is the subject of a controversial claim for evidence of life.
05: Earth’s Oldest Fossils
You continue your study of life's origins in the "top-down" approach, which works backward from known life forms toward a hypothetical common ancestor. This lecture focuses on rocks found in Australia that may contain fossilized cells that are the oldest record of living organisms on our planet.
06: Fossil Isotopes
Occasionally a dying organism is entombed in rock that is impermeable, allowing the original atoms and molecules of that organism to persist for hundreds of millions of years. Professor Hazen follows research on such samples, which provide intriguing evidence of early life.
07: Molecular Biosignatures
Even when evidence such as bones or shells is lacking, fossil elements, isotopes, and biosignature molecules point to the nature of primitive biochemical processes and give scientists their best hope for narrowing the time window for life's emergence.
08: Emergence
You turn to the "bottom-up" approach to life's origins, which starts with conditions on the primitive Earth and attempts to work out the chemical steps that must have occurred for life to arise. Crucial to this process is the new and exciting field of emergence, which this lecture explores in detail.
09: The Miller-Urey Experiment
In 1953, the landscape of research on the origins of life changed forever with the Miller-Urey experiment. For the first time, an experimental protocol mimicked plausible life-forming processes. As you'll see, the emergence of simple biomolecules is arguably the best understood aspect of the origins of life.
10: Life from the Bottom of the Sea
By the late 1970s, enough problems and questions had been raised about the Miller-Urey experiment that alternative hypotheses were proposed. One of the first and most influential of these competing models was the idea that life might have arisen in the deep ocean at a hot hydrothermal vent.
11: The Deep, Hot Biosphere
The hydrothermal-origins hypothesis prompted scientists to look for life in deep, warm, wet environments. And everywhere they looked—in deeply buried sediments, in oil wells, even in volcanic rocks more than a mile down—they found abundant microbes. You review the implications of these extraordinary discoveries.
12: Experiments at High Pressure
In order to explore the deep-origin hypothesis, scientists need a new breed of experiments. Professor Hazen gives a fascinating account of one of the first high-pressure experiments to test this theory, which took place in his own laboratory at the Carnegie Institution of Washington.
13: More Experiments Under Pressure
In this lecture you investigate some of the many possible directions of research to understand the possibility of life under hydrothermal conditions of high pressure. Such experiments are expensive, and Professor Hazen begins his remarks by discussing how origins research is funded.
14: Deep Space Dust, Molten Rock, and Zeolite
The last place you might think to look for life-forming molecules is the black vacuum of interstellar space. But new research is revealing that deep space is loaded with interesting organic molecules. You also explore two other surprisingly productive environments: igneous rocks and zeolite crystals.
15: Macromolecules and the Tree of Life
In this lecture Professor Hazen begins his study of the second great emergent step in the path from geochemistry to biochemistry: the emergence of macromolecules. Efforts to map the tree of life suggest that early life may have used a more diverse set of organic molecules than life does today.
16: Lipids and Membrane Self-Organization
Life had to develop some kind of protective membrane that isn't soluble in water. You explore two possible solutions to this problem, both of which involve fatty molecules called lipids. The amazing ability of lipids to self-organize was probably an essential step in the emergence of life.
17: Life on Clay, Clay as Life
The best way to assemble life's molecules in water is to "call in the rocks." In this lecture, you look at some of the ways that minerals might have played a role in selecting and organizing biomolecules. In particular, you focus on the ubiquitous group of minerals called clays.
18: Life’s Curious Handedness
This lecture explores an alternative approach to the selection and concentration of organic molecules that exploits the property of "handedness." Many molecules come in mirror-image pairs, like a left and right hand, and the processes of life prefer one "hand" over another.
19: Self-Replicating Molecular Systems
In the first of two lectures on self-replicating molecular systems, Professor Hazen shows that such systems are not necessarily alive, but they do have something like metabolism. The emergence of metabolism is a giant step toward understanding the origins of life.
20: Günter Wächtershäuser’s Grand Hypothesis
Which came first, metabolism or genetics? This may be the most fundamental scientific debate related to the origins of life. You examine views on each side of this question and focus on the most elaborate and comprehensive theory of metabolism-first—the iron-sulfur world of Günter Wächtershäuser.
21: The RNA World
Exploring the idea that life began with genetics, you study the RNA World scenario, which holds that the first life form was a self-replicating strand of RNA. There is abundant evidence that RNA is a truly ancient molecule that can fulfill the essential prebiotic chemical roles.
22: The Pre-RNA World
Before scientists can fully understand the origin of the RNA World, they must focus on what came before. By what chemical process did the first self-replicating, information-bearing system emerge? And if it wasn't RNA, then what was it?
23: Natural Selection and Competition
So far, one critical step in the transition from non-life to life has been left out—evolution. Competition helps drive evolution, and in this lecture you see how the struggle for resources among living chemical systems can lead to rapid evolution by natural selection.
24: Three Scenarios for the Origin of Life
Professor Hazen summarizes the course by reviewing three plausible scenarios for the origins of life: (1) life began with metabolism; (2) life began with a self-replicating strand of some genetic molecule; (3) life began as a cooperative chemical phenomenon, arising between metabolism and genetics.
About
Dr. Robert M. Hazen is Clarence J. Robinson Professor of Earth Sciences at George Mason University in Fairfax, VA, and a research scientist at the Geophysical Laboratory of the Carnegie Institution of Washington.
Professor Hazen earned his bachelor's and master's degrees in geology from the Massachusetts Institute of Technology. He earned a Ph.D. in Earth Science from Harvard University and did post-doctoral work at Cambridge University in England before joining the Carnegie Institution. At Carnegie, Dr. Hazen's research focuses on high-pressure organic synthesis and the origin of life.
Professor Hazen has authored 15 books, including the best-selling Science Matters: Achieving Scientific Literacy and The Sciences: An Integrated Approach. He has written over 220 articles for both scholarly and popular publications such as Newsweek, Scientific American, The New York Times Magazine, Technology Review, and Smithsonian Magazine.
He has received the Mineralogical Society of America Award, the American Chemical Society Ipatieff Prize, the Educational Press Association Award, the American Crystallographic Association's Science Writing Award, and Fellowship in the American Association for the Advancement of Science.
Professor Hazen serves on the advisory boards for The National Committee for Science Education, Encyclopedia Americana, NOVA, and the Carnegie Council. He appears frequently on radio and television programs on science.
