Most Helpful Customer Reviews
|
|
19 of 19 people found the following review helpful:
4.0 out of 5 stars
Genetic takeover, November 26, 2000
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.
|
|
|
12 of 12 people found the following review helpful:
5.0 out of 5 stars
Concise, logical, lucid, February 3, 2003
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.
|
|
|
8 of 8 people found the following review helpful:
4.0 out of 5 stars
Amusing and readable book about what the first replicators weren't, and might have been, like, March 2, 2006
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).
|
|
|
Most Recent Customer Reviews
|