Emergence on Earth . . . and elsewhere??
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Putting it back to front, Hazen lists the three likely scenarios for life's origins: a chemical process leading to metabolism, a chemical process leading to replication, or a combination of the two. The remainder of the book is an exploration of the ideas centered on the way life was started on this planet and the researchers who have conceived or tested them. The list of scientists involved is extensive, but in this finely crafted work, Hazen is able to introduce them, describe their work - and his own - clearly and effectively. With the advantage of arriving at "Life's Origins" studies from an "outside" discipline - geophysics - the author brings a fine sense of detachment to this presentation.
In any other account on this topic, the opening would inevitably be a reference to Charles Darwin's "warm little pond". The "warm little pond" idea was tested in 1953 by Stanley Miller, who figures significantly in this story. Darwin's "first cell" clearly required simpler precursors to be assembled and put in operation. As an earth scientist, Hazen is more interested in the role played by chemistry and physics than cell biology, and so begins the book with water's changing properties under increased temperature and pressure. This situation plays a more significant role in life's beginnings than we might guess, since one scenario for the initial steps lies deep in the Earth where water, essential to life, lies buried in rocks, hot and compressed. As it turns out, that water is home to living things - microbes that may not reproduce for over a thousand years, as contrasted with the microbes in your gut that reproduce every twenty minutes. It's a major change in scenarios, going from a little pond to the restrictive environment of the Earth's depths, but Hazen shows how each circumstance has contributed to better understanding of how life came to be. Further, the mechanisms are simple enough to be readily applied on any planet with a suitable environment.
The author weaves a number of research accounts into a broad tapestry he calls "emergence". The point of emergence is that there are no great leaps - life had to be built up through a succession of small, cumulative steps. Each step was a chemical process in the proper environment contributing some minimal change that ultimately became what we now call life. Carbon, he reminds us, is the key, but it does little by itself. Water is an essential factor, because its components are essential to building organic molecules. Each of the steps, so far as they are known, are described and fit into the role of life. More important, and in a significant departure from many books on this topic, Hazen describes the laboratory experiments that have verified suppositions or raised new possibilities about life's formation. Field work is not ignored here. The author describes the discovery of life around sea-floor vents and the implications of the Murchison Meteorite - which delivered dozens of types of amino acids - those famous "building blocks" of life to an Australian paddock. How do these highly diverse scenarios merge to produce the trees, pet turtles and people around us we see today?
That's what remains to be revealed. The gaps in the processes leading to the first true cell must be closed with descriptions of how various components came together. Many researchers have contributed to resolving those "hows" [there's more than one], and it's in this area that Hazen's three-option conclusion is so significant. For most organic chemical processes to take place, the operation requires protection from interference - a surrounding defensive environment. How does a complex carbon molecule build a protective "shell" while it's busy with its own affairs making new compounds? If the shell already exists - and those lab experiments now demonstrate how that can happen, how does the carbon assemblage break in and take sanctuary from a hostile world? Teasing out the answers to these questions has been the work of many scientists, particularly over the past couple of generations.
Life's origins researchers are an irascible lot, sometimes. It's a bit discouraging to read that Stanley Miller, who broke new ground [or perhaps not - German Walter Löb had performed similar work decades before], by generating amino acids in a flask, dismisses the notion of sea-floor vents generating life-promoting processes. And former astronomer Thomas Gold inexplicably rejects any contribution from space to the establishment of life here. The most compelling anecdote in this book however, is of an almost overage PhD student who works out how organic molecules can use - or adapt - the methods rocks use making in crystals. Nick Platt considers this establishes the underlying conditions needed for those molecules which "stack" in layers to create areas leading to the formation of "an information-rich molecule" - RNA, then DNA . Hazen negotiates these troubled conceptual waters with assurance, providing us with a compelling story - or set of stories - relating our beginnings. [stephen a. haines - Ottawa, Canada]
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Best book on the subject
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I have read several books about the origin of life the last frontier of science including Singularities by Christian De Duve and this was the best book by far it give us a comprehensive snapshot of "where we are" and come from a seemingly unlikely source: an earth scientist trained in mineralogy and crystallography.If you are interested on the subject just read it!
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Popular science review of life's origins
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Robert Hazen has put together a wide-ranging review covering all scientific aspects of research into the origin of life on Earth. Questions of this sort, which are about particular events, rather than general laws, are often, mistakenly, held to be non-scientific by those who would have us believe that their particular poetic or religious insight is intellectually respectable. On the contrary, the processes of evidence-gathering, analysis, hypothesis-generation and testing, apply with equal force in the Historical Sciences as the General ones. Hazen reviews the alternative sources of evidence (from chemistry and geology to molecular biology), gives a gentle insight into the analytical processes used by the research teams working on the question of origins world-wide, gives due weight to the competing hypotheses, and holds the readers' hands through a number of experimental tests. He does an excellent job of balancing the need for accuracy and informativeness against accessibility. The text is very light on equations and chemistry, and any reasonably smart lay-person could easily follow his arguments. He takes the now-conventional approach of dressing up many of the chapters with slightly breathless first-person narratives, but doesn't overdo this to a dsitracting extent. For those wanting an up-to-date, yet accessible and wide-ranging account of this field, Genesis could not be bettered. For those interested in drilling down deeper, the index, bibliography and Notes sections are very well done. Highly recommended.
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