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Seckbach J. Origins: Genesis, Evolution, and Diversity of Life

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Seckbach J. Origins: Genesis, Evolution, and Diversity of Life
Kluwer, 2004. — 740 p.
It seems almost certain that there was once an RNA word in which RNA functioned both as a genetic material and a source of essential catalytic activities. It helps to think of the problem of the Origin of Life as made up of three possibly overlapping sub problems. How did the RNA world come into existence? How did the RNA world “invent” the last common ancestor of life (LCA), a microorganism of the DNA/RNA/Protein world? How did the LCA diversify into the multitude of early life forms that we know from the fossil record or infer from extant life? This book has much to offer those interested in the first and last of these problems. The possibility that life exists elsewhere in the solar system or the Universe is another topic addressed by several authors.
The core of the book is concerned with the first problem. Life must have originated in an aqueous environment, but was it on a snowball earth, in a hydrothermal vent or on the shores of a temperate ocean? The bad news is that two of these hypotheses must presumably be wrong: the good news is that one of them is probably right. This is a frustrating problem that you can’t resist thinking about although you know that you are not likely to find a generally accepted solution, at least for the present. Fortunately, several chapters attempt to justify one or other of these different points of view and they make instructive reading.
How did the organic molecules involved in the earliest stages of chemical evolution accumulate on the primitive earth? Were they formed as a prebiotic soup when reactive intermediates that had formed in the atmosphere dissolved in surface waters and reacted together, or did they arrive in meteorites and comets? Maybe there never was a prebiotic soup, just a thin layer of prebiotic paste formed on and firmly stuck to the surface of minerals such as iron sulfides. All of these possibilities are explored. If you pay your money (to buy this book) you can take your choice.
Now we come to the most challenging problem of all. Let us assume that an adequate prebiotic soup or paste was available. How did the transition from chemical chaos to biological order come about? Darwinian selection must have emerged early as a source of complexity, but what was the first system to appear on the primitive earth that was capable of Darwinian selection? Was it RNA, some simpler covalent polymer of perhaps some non-covalent aggregate? Are there complex evolvable metabolisms that do not depend on a genetic material? You wont find definitive answers to any of these important questions in this or any other book on the Origin of Life, but here you will find them discussed from a variety of different perspectives in a stimulating way. You may even be tempted to do an experiment!
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