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The Demon in the Machine - Paul Davies *****

Physicists have a habit of dabbling in biology and, perhaps surprisingly, biologists tend to be quite tolerant of it. (I find it hard to believe the reverse would be true if biologists tried to do physics.) Perhaps one reason for that tolerance is Schrödinger’s lecture series and book What is Life?, which had a huge impact on molecular biology and with a reference to which, not surprisingly, Paul Davies begins his fascinating book. 

At the heart of the The Demon in the Machine (we'll come back to that demon in a moment) is the relationship between life and information. In essence, Davies points out that if we try to reduce life to its simple physical components it is like trying to work with a computer that has no software. The equivalent of software here is information, not just in the best publicised aspect of the information stored in the DNA, but on a far broader scale, operating in networks across the organism.

This information and its processing gives life its emergent complexity, which is why, Davies suggests, Dawkins-style reductionism to the gene level entirely misses the point. What's more, the biological setup provides a particularly sophisticated relationship between information and the physical aspects of the organism because the information can modify itself - it's as if a computer program could redesign itself as it went along.

The subtitle 'how hidden webs of information are solving the mystery of life' probably over-promises. As Davies makes clear, we still have no idea how life came into being in the first place. However, by bringing in this physical/information aspect we at least can get a better grip on the workings of the molecular machines inside organisms and how biology can do so much with so little. Here's where the demon in the title comes in. This is Maxwell's demon, the hypothetical miniature being dreamed up by the great nineteenth century Scottish physicist.

Maxwell's demon has the remarkable ability to tweak the second law of thermodynamics allowing, for example, heat to flow from a colder to a hotter body or, to put it another way, providing a mechanism for entropy (the measure of disorder in a system) to spontaneously decrease. Entropy has a strong (negative) relationship with information and Davies shows how miniature biological systems act in a demon-like fashion to effectively manage information.

There's lots to like here, from the best explanation I've seen of the relationship of information and entropy to fascinating coverage of how far we’ve gone beyond the selfish gene. This is not just about basic epigenetic processes (operating outside of genes, switching them on and off and so on) but how, for example, the electric field of a (biological) cell apparently has a role to play in ‘sculpting‘ the physical structure of an organism.

My only real complaint is that in part of the chapter Enter the Demon dealing with information engines and most of the chapter The Logic of Life, describing the relationship between living organisms and computation, Davies fails to put across clearly just what is going on. I read it, but didn't feel I gained as much information (ironically) as I needed from it. There was also one very odd statistic. We're told the information in a strand of DNA contains 'about 2 billion bits - more than the information contained in all the books in the Library of Congress.' There are about 32 million books in the Library of Congress, so that gives us on average 62.5 bits per book. Unless those are very short books, some information has gone astray.

Really interesting, then, from a transformed understanding of the importance of information in living organisms through to Davies' speculation on whether biological systems need new physical laws to describe them. But expect to come away feeling you need to read it again to be sure what it said.
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Review by Brian Clegg
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Comments

  1. Akshat26 February 2019 at 14:53

    Nick lane argues in his book The Vital Question that biological systems are not really working to decrease entropy they exist because they essentially dont violate the second law of thermodynamics . I wonder how that reconciles with the theory here

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  2. GT27 July 2019 at 01:00

    I find it difficult to follow some of this stuff. Not the fluffy conceptual models, but the simple aspergers stuff.

    eg p95, text describing Fig 11, says 'barred lines [indicate inhibition]'. Then seems to use a different term - 'loopy broken arrows' to denote self inhibition. Change of term is confusing but not fatal.

    But Fig 11 contains no broken or barred loopy arrows, only solid ones, thus indicating self activation, not self inhibition. Again, I guess, not fatal, if the reader is expected to be alert for errors or misprints.

    But table 2, P96 shows that in at least 2 cases, the loop is self suppression, so the loop should be broken or barred. Still not quite fatal.

    But then, following Table 2 and Fig 11 together, node G suddenly gets activated in step 8, although in Fig 11 there is no 'incoming [activation] arrow' pointing at it, except for it's own self activation loop, which can never be initiated.

    So what's going on? AFAIK just errors, which I'd hope not to have been included in this book.

    So, how do we read this book? Perhaps best just to gloss over all the clever diagrams & tables, say 'Gee, Whizz, that's all amazing!'

    OTOH if I'm really not understanding a perfectly valid exposition, I'd love to know.

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