“The Equations of Life: The Hidden Rules Shaping Evolution“, written by Charles Cockell, published in Europe by Atlantic Books in June 2018 (hardback, 339 pages)

That physics imposes hard limits on life is not necessarily a novel idea. D’Arcy Wentworth Thompson’s 1917 book On Growth and Form already put forth the idea that morphology and growth are dictated by physical laws and can be described mathematically. And Vogel’s 1989 book Life’s Devices: The Physical World of Animals and Plants is a great, if slightly dated, introduction to biomechanics. Cockell starts off at the level of animal groups such as insect communities and flocks of birds to show how simple mathematical rules can lead to the emergence of complex behaviours. And, like above books, he discusses how the form of organisms is dictated by physics, touching on some of the power laws and network-like properties that George West discussed at length in Scale: The Universal Laws of Life and Death in Organisms, Cities and Companies. There are plenty of equations, some simple, some complex, although they are really only there to illustrate his point. I was expecting the book to stay at this level and discuss how various laws of physics limit the possible outcomes of evolution. What I wasn’t quite prepared for was the giddy tumble down the hierarchies of life in the rest of the book, but was I ever so pleasantly surprised.

Starting with cells and how physics explains why they developed, the book then considers DNA and proteins, offering an explanation of why we have four different base pairs in DNA instead of six or more. On a smaller scale, life is about acquiring energy which is achieved by transferring electrons across cell membranes (in The Vital Question: Why is Life the Way it is?, Nick Lane considered this to be life’s ultimate linchpin). Further down still, water (and not another solvent) is used as the medium in which to carry out biochemical reactions, and life uses a very limited set of atoms as its predominant building blocks. At every turn, Cockell shows how physics explains why life has preferred the solutions it has preferred, and how proposed alternative solutions (such as life forms based on silicon instead of carbon) would not work as well.

“physics is life’s silent commander”

Cockell is a professor of astrobiology, a discipline that studies early biology and origins of life in the universe, as well as the possibility of extraterrestrial life and what it might look like. Amongst the many books he has written on the subject is the undergraduate textbook Astrobiology: Understanding Life in the Universe. The abovementioned descent down the hierarchies of life is at the same time an excuse for him to speculate what these findings mean for life elsewhere in the universe. Cockell clearly enjoys his forays into this topic, throwing in a short overview of exoplanets as a bonus (for a fuller picture of that, you can take your pick from at least four current or forthcoming pop-science works, which I link to below). Based on the fact that many principles of physics apply throughout the universe, he makes a strong case for extraterrestrial life likely resembling life forms as we know them on earth, speculative zoology and science fiction notwithstanding.

To long-time readers of this blog, the question of the predictability of evolution might sound familiar. Indeed, it was also explored in Losos’s book Improbable Destinies: How Predictable is Evolution?, the first book reviewed here. Cockell acknowledges this book several times in his chapter notes, and throughout the book he considers whether what we see in living organisms is a consequence of convergent evolution (life independently evolving the same solution repeatedly) or contingency (the result of chance events that could work out completely different if we could repeat the evolution of life). He recaps Losos’s discussion of the main players in this debate, namely Stephen Jay Gould, who was a proponent of contingency (see amongst others his book Wonderful Life: The Burgess Shale and the Nature of History), and Simon Conway Morris, who was a proponent of convergent evolution (see amongst others his books The Crucible of Creation: The Burgess Shale and the Rise of the Animals and The Runes of Evolution: How the Universe Became Self-Aware).

“[Cockell] makes a strong case for extraterrestrial life likely resembling life forms as we know them on earth, speculative zoology and science fiction notwithstanding”

In the end, your answer to this question depends on your perspective. Cockell is willing to concede that, yes, if you focus on the details, the variety of life seems bewildering and unpredictable, and there seems to be a lot of contingency. But to him this is just icing on the cake. When you zoom out and consider life on a more fundamental level, the outcomes of evolution are highly predictable, and convergent evolution is the rule. From his vantage point, that of physics circumscribing the limits of life, life has almost no other choices. Maybe, just maybe, if we discover life elsewhere in the universe, we might find some very exotic solutions to life’s basic needs, but Cockell convincingly argues that these will be the very unlikely exceptions occurring under the confluence of very exceptional circumstances.

Written with enthusiasm, in turns lyrical and infused with a dash of humour, The Equations of Life is a pleasure to read. In a few places, Cockell assumes perhaps just a little too much background knowledge of physics on the part of the reader, such as when he casually talks about the various orbitals and suborbitals that electrons can occupy in an atom. I also think that for a popular science work of this calibre, the book could have used illustrations of basic concepts in places. Overall, however, I think Cockell does a marvellous job of presenting complicated and abstract concepts in an understandable way. Both convergent evolution and the role of physics in biology have been written about before, but with his background in astrobiology, Cockell presents a unique take on the subject that comes highly recommended.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.

The Equations of Life paperback, hardback, ebook or audio CD

Other recommended books mentioned in this review:

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Some recent popular science books on exoplanets:

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“Scale: The Universal Laws of Life and Death in Organisms, Cities and Companies</span>”, written by Geoffrey West, published in Europe by Weidenfeld & Nicolson in July 2017 (hardback, 481 pages)

The science of complexity studies that wonderful phenomenon of emergence: when collections of individuals (molecules, cells, people etc.) aggregate and things start to happen that you did not or could not predict based on the properties of the individuals. It’s the whole being more than the sum of its parts. It’s simple rules giving rise to complex patterns. It’s hard to give an exact definition, says West, but, to paraphrase a certain US judge, “you know it when you see it”. The scaling and scalability West is interested in, then, is how things change with size. As it turns out, many properties don’t simply double when something doubles in size (i.e. in a linear fashion), but either increase slower or faster (sub- and superlinear scaling in jargon).

This is something we are all intuitively familiar with. The phrase “economy of scale” has crept into everyday speech with the rise of large corporations such as Amazon. And most of us will be aware that the Richter scale, telling us how strong earthquakes are, is a logarithmic scale (an increase of one unit corresponding to a tenfold increase in amplitude).

After the US government in 1993 cancelled plans to build the SSC, a huge particle accelerator to be used for physics experiments, West and many other physicists found themselves subjected to the sentiment that the era of physics was over: the 21st century was to be the age of biology. With feathers properly ruffled, West decided to apply the quantitative, analytical and predictive thinking typical of physics to open problems in biology. Already in his fifties at this time, age, death and mortality were subjects of particular appeal. But, to West’s surprise, there was no proper mechanistic theory of ageing. Why do humans live for about a hundred years? And why do smaller mammals live shorter lives?

“[…] complexity […]”you know it when you see it””

The first two chapters to delve into West’s research are, for a biologist, an absolute pleasure to read. The famous biologist Julian Huxley coined the term allometric scaling to describe how certain properties of organisms scale disproportionately with size (e.g. elephants have relatively thicker legs than mice once you correct for the difference in length). However, allometric scaling affects more than just morphology, it also affects physiological mechanisms such as metabolism. West’s findings that the underlying geometric properties of the networks that deliver energy, materials and information to cells (e.g. the system of blood vessels) dictates general properties and limits, is one of the many “aha” moments that this book delivers. I will not try to summarise his argument here, but suffice to say it makes beautiful sense and is well presented. It allows us to explain why mammals can’t get smaller than shrews or bigger than whales. Why we stop growing with age. Or why larger animals live longer.

But networks for distributing stuff (whether this is material goods or immaterial things such as knowledge) are everywhere. And West being the polymath he is, the book then branches out to describe how his subsequent research and collaborations have tried to apply these network principles to cities and companies. In his opinion, cities are one of the greatest human inventions, having afforded a stage for many of the social and economic developments of the last two centuries to play out on. Rapid urbanization is generating many challenges that apply to cities everywhere (water availability, environmental impacts etc.). So, can the network principles observed in biology be applied here to describe, understand and predict the growth, dynamics and evolution of cities and companies? West’s findings suggest yes: the urban pace of life, crime, income, and many other things scale in a non-linear fashion when size increases.

Similarly, though West admits this is still very much work in progress, more recent work has been applying these ideas to ask if we can formulate a science of companies. Whether looking at company income, profits, or age, non-linear scaling patterns are found when comparing large numbers of companies across the globe.

“[…] that the underlying geometric properties of networks […] dictates general properties and limits, is one of the many “aha” moments that this book delivers”

A final chapter then asks if and how the accelerating pace of life and socio-economic development is sustainable. He thinks not (and I agree with him), and he goes to some effort to stress that his reasoning is not just another rehash of Malthusian arguments (a topic on which I hope to write more at some point). Opponents have pointed out that Malthus and later thinkers were mistaken by not taking into account human ingenuity and innovation, which have repeatedly saved the day. For now. But West makes a great point that even this tempo of breakthrough innovations (or paradigm shifts) is not scaling linearly with time. How to avert societal collapse is not something he has an answer to, but it certainly doesn’t lie in persisting in continued, open-ended growth.

Despite being a biologist, I found these later chapters very interesting, and here, too, moments of great insights will occur while reading. I do feel that this is where the book starts to lose focus a bit. Given how far removed the topic is from what I normally read and what I know, West does a great job at not making me lose interest and at keeping me on board, making me understand what he is talking about. But he does wander a fair bit, throwing in regular preludes, interludes and other digressions. And that’s before I mention the many anecdotes and introductions to co-workers. It’s not that the digressions are not interesting, nor that the anecdotes are not amusing. By and large they are, but the cohesiveness and focus of the book suffer somewhat in my opinion. An 8-page postscript / acknowledgement section in small print seems symptomatic of this, and buried in there are kudos to the editors who have pared down an even bigger initial manuscript. A further niggle is that the reproduction of certain graphs (especially those containing data points for multiple categories) in greyscale doesn’t really work. Although they get across the general message, they were clearly designed with colour in mind and in my opinion should either have been reproduced in colour, modified to be comprehensible in greyscale, or just left out.

Nevertheless, Scale is a book of exceptional breadth that talks about some really big ideas in a comprehensible manner. It’s the kind of book that doesn’t come along often, written on the back of a long and rich career. If you don’t mind taking your time and being led around many ideas, then Scale is a great book to sit down with and will provide plenty of food for thought.

Disclosure: The publisher provided a review copy of this book. The opinion expressed here is my own, however.