Non-Fiction Reviews

Revolutions that made the Earth

(2011) Tim Lenton & Andrew Watson, Oxford University Press, £29.95 / US$52.95 / Can$51.20,
hrdbk, xii + 423pp, ISBN 978-0-199-58704-9


Occasionally, very occasionally, a general science book crosses my desk that makes me drop everything: Revolutions that made the Earth is one such book. I immediately skimmed the contents to settle on an area of personal interest, but before I knew it I had finished that chapter, in the course of which was drawn to a reference a couple of chapters earlier and so read those too.   Big mistake! Suddenly I realised that a couple of hours had passed and that I was really going to have to go back to the beginning and read the book thoroughly from the start. When a book does that to you, you know you have something really special.

Before going any further, let me explain who might really benefit from this book (as after all if you are not one of those then this review – which I suspect may end up being lengthy – will not be of much interest).   First off, potential readers are going to have to have a background in undergraduate-level science, or at least be self-taught to that standard. It does not unduly matter in which science potential readers have qualified as the authors do a commendable job of bringing readers up to speed in the various (and there are a number) of specialist areas on which their case rests. So if you have a grounding in, and a real passion for, science writ large then this book could well be for you.  Second, the book will be of interest to anyone who wants to know about the geologically-spanning dance between life and the (global) environment. Third, this book is absolutely critical to those studying exobiology (or 'astrobiology' as newbie trendies call it) as it presents a solid case for some of the key features of Earth-like planets, and so has implications for life (especially complex life) elsewhere in the Galaxy (hence Universe) through an examination of our own world.

With regards to the core regular visitors to this site (scientists who enjoy science fiction and who, of course, can readily distinguish between the two), it is the evolution of the Earth's biosphere and its Earthlike exoplanet implications that may well grab them in addition to the science itself.  After all, a proportion of hard SF deals with issues in deep time (time over a geological scale) and with the state of whole planets.  Then there are SFnal issues such as the Fermi paradox of which the subject matter of this book has considerable implications, and on which the book itself briefly (very briefly) touches.

Additionally, this book will be of relevance to some scientists who have no interest in SF and here, in addition to exobiologists, those involved in biosphere (Earth system) sciences will find this an absolutely fascinating if not an essential read.

Hopefully the above two paragraphs will help you decide whether this book is for you. Those of you who know me will know that my interests encompass a number of the above areas. My own undergraduate textbook on climate change biology and human ecology (1st edition 2007, and 2nd currently being revised and expanded for 2013) devotes a good quarter to past climate change and a whole chapter on climate change in deep time. This is integral to understanding the current global warming issue because the evolution of life has affected our global climate and planetary state, and you need to be aware of this if you are to appreciate the significance of what our own species is now doing to the climate system and the consequential implications for the future. In short I am familiar with many of the science elements within Tim Lenton's and Andrew Watson's book.

To distil the authors' complex synthesis into a few lines is difficult, but in essence their case is this. Life arose (surprisingly) early in Earth's history before evolving. In doing so you may think that there are many evolutionary stages between life's origin and us (intelligent, technology-wielding) observers today: as the authors say, if you are reading this, you qualify as such an observer. However, as the authors convincingly argue, there are surprisingly only really only three key stages (perhaps several intermediate ones of lesser criticality/evolutionary difficulty), absolutely necessary to get from the origin of life to us as intelligent, third stage, technological observers. Furthermore, these key stages (the revolutions in the book's title) have some common features. These centre on carbon cycling (after all life on Earth is carbon-based) and how it relates to the global climate.

Now, while the above description may seem simple, the actual case they present is based on a considerable body of evidence gathered from disparate specialist areas of biology and geology as well as underpinned by some simple (if you understand the notation) yet intellectually challenging maths, not to mention observations gleaned from astronomy, all of which are thoroughly referenced. This book is a scholarly work. (And do not worry, you do not have to look up and read the maths papers referenced to follow the book's line of arguement.)

It has to be said that those without any background in science may well, if not will, struggle. This is not because the authors' argument lacks coherence, but because its supporting evidence-base is so broad and the authors do go into some detail (almost wonkishly so) in describing the key exhibits they use to make their case. Having said that, for example, they do give one of the best of the brief summaries as to how photosynthesis works I have come across over many years. Furthermore, there is nothing wrong in being wonkish if presenting an integrally complete case is the goal. Nonetheless, some may find the authors' rigour causing them to stumble in their reading. My advice is that providing you can cope with most of the book, it does not really matter if you skate over two or three of the chapter subsections. This is not a problem as the authors introduce each chapter as well as each of the book's sub-dividing parts. There are also end-chapter summaries. All of this means that it is possible to keep in touch with central case being presented even if some sections are simply skimmed by readers. (Readers can always go back to these later if they feel the need, and a complete reading of the book is to be encouraged.)

For the most part the style of writing is of the proverbial New Scientist level: perhaps occasionally dipping into Nature 'News & Views' complexity. (Nature's 'News & Views' section being the part of that journal that places subsequent research papers in that issue into a broader scientific context as well as providing an aid for those reading across disciplines.) Indeed occasionally, as with the book's first chapter, the writing style is positively Carl Sagan-ish. (I even checked Sagan's Cosmos to see if the authors lifted, or paraphrased, any text: they had not from what I could see from a quick peruse.)

Now, I had wondered why the authors had not provided a simpler account for a wider readership, and the answer here (I think, and I admit I may be wrong) is that the authors are doing two things that editorially do not entirely lend themselves to each other.   The first is that they are presenting a reasonably fresh approach to the story of life's evolution and the planet. Though many of the elements of their case have been around for a while (the book is amply referenced) I have a feeling that this book is the first coherent presentation of this 'critical carbon life evolution revolutions' picture, and for which the authors truly deserve credit. (Previously there have been papers, articles and books that in part refer to such a few number of critical steps but this book I think is the first devoted exclusively to this.) And so in part the authors are speaking to fellow academics and this is them nailing their flag in book form to the academic mast.  The second thing they are doing, which is quite different, is providing a fascinating story that will appeal to many aficionados of popular science books. Indeed while there are countless books on 'early' life especially dinosaurs (which actually are late-comers), this book pays considerable attention to really early life before the Cambrian boom (around half a billion years ago) and how it is we know what we do about such truly ancient times back to over 3.5 billion years.   The difficulty comes is that speaking to fellow academics, and also conveying a message to a broader readership, arguably does require two different levels of comprehensibility: catering for both is not easy. Time will tell, through the book's sales, how well the authors have succeeded in both these disparate missions.

Yet, as hugely worthy is this book, I am though a little disappointed that a number of simple things were not done.   Why on Earth was not a geological table included?   Why were not abbreviations spelled out in their first usage within each chapter?  And then there were the occasional contradictions. For example, on page 50 we are told that stellar synthesis did not favour nitrogen which is why nitrogen is a potentially limiting nutrient for plant growth, but then the next page it is pointed out that the atmosphere is awash with nitrogen but it is its triple N-N bond that's the stumbling block.  Then again on page 383 we are told that global population is set to stabilise between 8 – 10 billion, but on page 399 are told it will be at least 10 billion by the end of this century.  Now most books (and my own writing is no exception) have typos and tiddler mistakes, but outright contradictions are not only annoying but do confuse and particularly so when speaking to those across disciplines. Arrghhhh!

(And I am not going to mention my bugbear in loathing the term climate 'tipping-point' as this suggests that there is a specific 'point' about which the climate shifts to a new state and that returning to that 'point' will flip the climate back again. This is not always true: often it is not. A flip from one state to another may occure at point 'b' but to flip back again you have to go back to another point 'a': there is no single 'point' about which systems flip. Climate 'threshold' is -- I personally ontend -- a more representative term. Sorry Tim Lenton... And yes I did just mention this is just a 'personal' bugbear. Feel free to ignore it.)

Now I mention that the book needs a little tidying up is not to have a go at the authors but because this book really is so important that it will no doubt get a few printings and in time will hopefully deserve a new revised edition.

As mentioned, this book's science draws upon many disciplines.  Indeed while there is much corroboration across disciplines in some areas (such as physics and material science, or ecology and meteorology) I have found in my work of many years with learned societies that it is surprisingly difficult to get scientists from different backgrounds to actually take time to engage with each other, even if generally we all think it would be a good idea to do so. This book's multi- and inter-disciplinary approach is one of the book's strong points and I bet that nearly all scientist readers will gain some new insights. (Non-scientists will struggle as this book is academically heady: academics will love its challenges.)

By now you will have gathered thatI firmly commend this book and await to see if it sparks new thinking in biosphere evolution in wider scientific circles.  Meanwhile if you are up for a polymathematical science intellectual tour de force, and are interested life's evolution on potential Earthlike planets, then this book is a real treat. As regards the specialist, if you are working in exobiology (or even astrobiology) then Revolutions that made the Earth really has to be an absolutely essential, 'must read'.

(Yes, as I suspected at the start, this really was going to be a lengthy review. My thanks to those of you who made it this far to the end.)

Jonathan Cowie


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