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Seven Clues to the Origin of Life: A Scientific Detective Story (Canto)

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This reference, intended for the general reader, treats the problem of the origins of life on Earth as a Sherlock Holmes mystery to be solved. The reader is introduced to organic chemistry and the workings of an E. coli, to show how difficult it is to get chemical systems to produce products such as RNA or DNA, and yet, how very complex a simple cell is. It is suggested that perhaps instead of thinking classically as DNA as the controlling element and core of the cell, ie, DNA-> RNA-> proteins, think from a supply perspective, ie, at the core of the cell are carbon molecules such as carbon dioxide -> subcomponents -> amino acids -> nucleotides & DNA, ie, DNA is not at the core, but is most outward layer, and probably evolved the last too. It is proposed that the ultimate ancestor of life on Earth did not use RNA or DNA as a genetic system, but with evolution, a 'genetic takeover' occurred whereby the now-familiar RNA and DNA systems emerged. The phenomenon of self-assembly of molecules, from soap bubbles to the folding of proteins to the formation of crystals is discussed. This leads to the proposal that the very early genes on Earth were in fact 'crystal genes'. The crystallization of supersaturated solutions is discussed, and it is noted how small crystals cause 'reproduction' and 'growth' of more crystal from the supersaturated solution. Geological processes on Earth produce huge amounts of clay minerals. Crystals all have defect structures, with the result no two crystals are identical. The first 'lifeforms' on Earth were inorganic crystal-based entities that reproduced and grew as such. Since the supply perspective of the cell suggests that the biochemical structure is built up from carbon dioxide molecules, it is proposed that via photosynthesis the mineral lifeforms started producing organic molecules. It is noted that iron atoms are common in most clays, and could have 'caught' light and in conjunction with various patterns of clay layers, have synthesized organic molecules. Eventually the clay apparatus of the primitive lifeforms was replaced with RNA-like molecules, amino acids, membrane layers, and so on, and the DNA/RNA/protein form of life we are familiar with emerged. The seven clues referred to in the title of this reference are as follows: 1. Evolution can only occur when there is replication of some sort of genetic information. 2. DNA and RNA are difficult molecules to fabricate, far removed from the core of biochemical pathways. 3. To make an arch of stones needs scaffolding, and similarly, to originate the form of life we are now familiar with required some sort of scaffolding. 4. No particular fiber in a rope has to stretch from one end of the rope to the other end as long as they are adequately intertwined, and similarly, the lifeforms based on inorganic crystalline genes could have gradually evolved into lifeforms based on organic molecular genes. 5. A primitive machine must be easy to make from available materials and work with little fuss, while in the case of an advanced machine, the emphasis is on working well, and often it may be complex to assemble. 6. Crystals put themselves together and could have easily formed a 'low-tech' genetic material, unlike the complicated control required of organic molecules. 7. The Earth produces huge amounts of clay minerals.

A. Graham Cairns-Smith has created a small gem in his Seven Clues to the Origin of Life. The book, a discussion of the pre-biotic stage of the evolution of life, is concise, logical and lucid and explained in terms that would be comprehensible to anyone from the junior high student with a basic science education to beyond it. As Daniel C. Dennett writes in the journal Nature about another of the author's books, "Cairns-Smith is a brilliant explainer of difficult ideas, bringing to the task an imagination that is magnificently disciplined by detailed scientific understanding."

I had heard of the concept of a crystal template for the creation of organic molecules while studying mineralogy for a geology degree in the 1980s, so Cairns-Smith's topic had already intrigued me. When I found reference to this book in the annotated bibliography of another I was reading, I decided to look it over too. I wasn't disappointed.

Dr Cairns-Smith is an Honorary Senior Research Fellow in the Chemistry Department at the University of Glasgow in Scotland. The main area of his research has been in simple non-nucleic acid genetic systems which might have been important in the earliest stages of the evolution of life, a topic on which he has collaborated with others and continued to publish in professional journals as recently as 1996. So he is eminently prepared to discuss the pre-biotic era of life.

Although the book is old for a work of science (1985), it is nonetheless still very much a leading idea in the subject of the early stages of life. Furthermore, the author cleverly puts the topic into terms that most of his readers will understand, even borrowing concepts from architecture/building, the nature of ropes, and the history of technology to do so. Avoiding confusing professional jargon, he leads the reader through the material in a logical, step by step manner until his conclusion: that we may owe our existance to the character and evolution of clay materials. While one may not necessarily believe that this is actually how the process worked-or for religious reasons may disagree altogether-it is still a cogent work, one that illustrates how science comes up with its theories of how things got to be as they are.

I found this book while doing some research in the aftermath of an online discussion of just how unlikely the formation of the first replicators (the first things that could undergo evolution) was.

In that discussion someone had remarked (after reading some creationist stuff) that it was just fantastically impossible for the first cell, or even the first nucleotide, to come together more or less by accident. I replied that of course no one serious thinks that the first replicator was a whole cell, or even a modern sort of nucleotide; it was presumably some very low-tech and inefficient thing, just barely able to reproduce itself imperfectly once in a blue moon. After I said that I realized that while it seemed perfectly obvious to me, and that all right-thinking people must agree, I didn't specifically recall any of the right-thinking people in question. So I went and did some research, and (among other things) I found this book.

In "Seven Clues to the Origin of Life", A. G. Cairns-Smith, a molecular biologist and so on at the University of Glasgow, lays out in an amusing and chatty way (including numerous Sherlock Holmes quotations) his argument that yes the first replicator really couldn't have been any of the replicators that we have today, or even anything very much like them. And he presents his own theory as to what they in fact were: inorganic clay crystals of a certain type that seem to have (or seem capable of having) both the requisite ability to do a kind of very low-tech replication, and the potential to have eventually provided the platform on which our current much higher-tech replicators (DNA and all that) got their start.

The writing is extremely clear and readable, aimed at a general non-technical audience, and the book is both fun and short (131 pages including glossary, index, etc). I'm not convinced by his argument that these particular clay crystals were the first replicators, but I'm very convinced that something at least vaguely like them could have been, and that therefore there's no really puzzling problem about how replication got started in the first place. Which is nice, because it's pretty clear that it did. *8)

Highly recommended to one and all. And if you really like the subject, there's apparently a longer and weightier and more technical book, "Genetic Takeover", in which he treats the same subject in more detail (and perhaps without the Sherlock Homes).

First, I have to preface my review by saying that I haven't yet read other books about the origin of life, so I have nothing to compare this book to...anyway

This short book is absolutely fascinating. The thrust of the author's argument is this:

Life as we know it is too complex to have originated in its present form. Nucleic acids and proteins and most organic molecules necessary for life are too complex to have originated in the primitive atmosphere even if the conditions were favorable. We need to find something that is capable of growing, replicating (not perfectly), and providing a substrate for the formation of molecules necessary for life as we know it today. What could possibly do that? Ah yes, crystals of clay! Clay is abundant. It grows and replicates but not perfectly thus allowing for irregularities to accumulate. These crystals with irregularities could then provide a surface that brought molecules together in close proximity so that they could interact and produce the organic molecules needed for life. Eventually, the secondary organisms that resulted from this process achieved a certain complexity that gave rise to life as we know it.

Interesting argument. Is it true? Is it even plausible? I actually don't know the answer to either question, and I have a feeling that there are no definite answers.

I found this book thought-provoking, and it presented an interesting solution to the mystery of the origin of life.

Cairn-Smith's "7 Clues" consist of six clues and one broad speculation. But that hardly detracts from its value. (What's more, he may well be correct.) The book is easy to read, and does an outstanding job explaining problems associated with understanding the chemical origins of life. Beyond that, however, Cairns-Smith does an admirable job of demonstrating that chemical reactions we would assume were simple, mechanical processes are nearly as elaborate as those that result in the "miracle" of life. I would have liked a more detailed explanation of the chemical mechanics of the inorganic-organic transition -- Cairns-Smith leaves this largely to the reader's imagination -- although I probably wouldn't understand the explanation if I read it. Still, Cairns-Smith has suggested something profound; I hope research in molecular biology and chemistry seriously investigates this suggestion.

Although I'm not too enamoured by Cairns-Smith's idea that clays were the origin of life, this book does a good job explaining his point of view. It's a short book but covers quite a bit of the science involved with trying to dissect how life is arranged today and how it may have begun. If you're worried about his "clay" theory being a clandestine attempt to say the Bible was right after all, it's not.

How would Holmes and Watson investigate the curious case of life on earth. A.G. Cairns-Smith, shows us using the great detective's techniques (with great quotes from his many other cases) how life must have begun on earth. His is the only explanation I've ever read which understands that half of evolution was needed just to get to DNA. The seven clues are listed in a summary at the end and present the best explanation of how life could begin from inorganic chemicals - which as he shows, it must have done so.

I reread this book every year, right before I present the origin of life in my historical geology classes. I spend an entire lecture on this book. The topic and the ideas presented by the author enthrall my students. Someone always asks to borrow it. One of the great things about this book is that my students, even the first year students, can understand it. The ideas presented by Dr. Cairns-Smith make much more sense to me than other ideas I have seen presented on the origin of life on Earth.

Modern genetic components are too complex to have appeared by chance on the primordial Earth. DNA and RNA, and even their more elementary building blocks, require the assistance of an agent at least as complex as themselves for their synthesis. This is the famous Catch-22 of the origin of organic replicators. Cairns-Smith begins by clearly stating this problem, and then embarks on an innovative and imaginative journey to find its solution.

It is no shortcoming of this endeavor that a solution is not presented. Cairns-Smith traces the outline of a proposal: 'low-tech', inorganic replicators -- crystal genes in solution -- with the ability to carry information and reproduce, to 'mutate' and evolve, proliferated over long periods of time near the surface of the primordial earth. Clay is identified as a likely source for this crystallization, being stable and ubiquitous in this environment. The regime change from inorganic to organic information carriers arrives in the form of a "genetic takeover", in which organic molecules come to supplant their mineral forefathers. Cairns-Smith describes an intricate dance of the inorganic and organic, as the molecular keys to life -- amino acids and nucleic acids -- were built up amongst the crystalline scaffolding in environments primed for their creation. From here Cairns-Smith speculates on how this major transition to organic information carriers might have completed...

This book is clear, concise, and packed with courageous ideas about a time shrouded in mystery. Although current research favors alternative ideas over Cairns-Smith's crystal genes, aspects of his development remain relevant to today's thinking, and this book is an important and especially accessible early contribution to the understanding of abiogenesis.

I am impressed that this paperback is still commanding a price of $20 on Amazon. It just shows how remarkable this little book is. I still maintain that the best literature and the best scientific thought comes out of Britain. This is another example. With nothing more than reflecting on how life began and asking the right questions, separating the VITAL from the INSIGNIFICANT, Cairns has provided an interesting suggestion, and lays out the thesis so well, you can't help but follow along easily. My only complaint: once he reaches the end, I wish he had added a chapter or two to suggest what the next step was in evolution of the first organism. It's a short book; you can read it in two or three days at a very leisurely pace. I first read it some years ago, and re-read it occasionally, and always find something new.