This is the unedited version of a review of mine from the Wall Street Journal
Life on the Edge:
The coming of age of quantum biology
Johnjoe McFadden & Jim Al-Khalili
There is a sense in which all of biology is quantum biology. The entangled strands of DNA, the famous double helix of the molecule of life, are held together by a quantum phenomenon known as hydrogen bonding. The way in which those strands untwist and build new double helices during the process of reproduction is at heart a quantum phenomenon, closely related to the way in which quantum entities such as electrons can be both wave and particle at the same time.
But in this remarkable book Johnjoe McFadden, an expert in molecular genetics, and Jim Al-Khalili, a quantum physicist, join forces to explain many everyday aspects of life in terms of what is often referred to as quantum weirdness. They do so, moreover, in an easily accessible style, free from jargon, which makes complex issues clear even to the non-scientist.
After teasing the reader with an introduction presenting the puzzle of how birds can detect the Earth’s magnetic field and use it for navigation, the authors lead us gently by the hand through discussions of the nature of life itself, right down to the molecular level, and the mysteries of quantum physics. This is material which has been covered in many books, but nowhere more succinctly and clearly than here.
Thus prepared, we are ready for an explanation of what they call “the quantum robin” – the workings of the magnetic sense organ in birds and other animals. It turns out that this ability is linked to a phenomenon known as “entanglement” occurring in certain molecules in the appropriate sense organ. Entanglement involves two or more quantum entities, such as electrons, being in some sense in tune with each other, so that when one of them is prodded the other one twitches. And in certain circumstances, as McFadden and Al-Khalili explain, this makes the molecules involved sensitive to the direction of a magnetic field.
This is a profound realisation, because entanglement is such a bizarre concept, to the human mind, that for decades even many physicists doubted that it could be real. Albert Einstein famously referred to it as “spooky action at a distance”. The equations tell us that once two particles have interacted, then forever afterwards, no matter how far apart they are, a measurement of one particle will instantaneously affect the properties of the other particle. As Einstein wrote to his friend Leon Rosenfeld, “is it not paradoxical? How can the final state of the second particle be influenced by a measurement performed on the first, after all physical connection has ceased between them?” He believed that this highlighted a flaw in quantum theory, and went to his grave still looking for a better description of the Universe. But he was wrong. In the 1980s (and repeatedly since), experiments involving photons, the particles if light, have proved that the spooky action at a distance is real.
In that case, it should be expected that natural processes make use of it, just as living things make use of sunlight for photosynthesis. Why should they? Because it is there. Life uses whatever is available, whether that thing is food, energy, or the laws of physics. So it should be no surprise that the phenomenon of entanglement is not used solely by European robins. Monarch butterflies and fruit flies are among the other species which make use of quantum effects in navigation. Nor are quantum processes confined to the animal world. Photosynthesis is the basic mechanism in plants which provides the energy that is used to manufacture plant material, and ultimately the food we eat, out of basic chemicals such as water and carbon dioxide. This, too, depends on quantum processes which “push” the absorbed energy of sunlight in the right direction.
Pre-quantum physics, the laws discovered by Isaac Newton, is often referred to as classical physics. “Most biologists’” the authors point out, “still believe that the classical laws are sufficient. With Newtonian forces acting [to explain photosynthesis] in strictly classical terms . . . with light acting like some golf club able to whack the oxygen golf ball out of the carbon dioxide molecule.” But, as with Einstein and spooky action at a distance, they are wrong. The key step in the process involves electrons “hopping” from one molecule to another in an orderly fashion. Some extraordinary experiments described in this book (in what is admittedly a slightly more technical passage) have revealed that energy is flowing through such a system by, in effect, following several routes simultaneously, thanks to a phenomenon known as coherence. This is a purely quantum effect.
The discovery is particularly exciting because quantum physicists working on the development of computers that operate on quantum principles incorporate quantum coherence into their designs. Not for the first time, nature got there before the scientists, and so far does a better job of “computing” the most efficient way to get energy from A to B. Not that the quantum computer scientists were quick to embrace the idea. Al-Khalili and McFadden quote one of those researchers describing his colleagues’ immediate reaction, when they saw a New York Times article suggesting that plants might operate as quantum computers: “it’s like, ‘Oh my God, that’s the most crackpot thing I’ve heard in my life’”. But they have since changed their tune.
All this is dramatic enough, and well worth the price of admission. But the authors have saved the best – if admittedly the most speculative – idea for (nearly) last. These speculations involve consciousness and the mechanics of thought, but also the processes that go on inside quantum computers and, we now know, during photosynthesis. By tracing back the process of painting a picture (they imagine an artist in Palaeolithic times painting a picture of a bison on a cave wall) from the fingertips of the artist through the muscles and neurons in the arm to the brain, they focus in on the chemistry involved. At one level, this is an entirely causal, mechanistic chain of processes, like that of a machine. But who, or what, is in charge of the machine? Who is pulling the levers?
It is an old question, going back to philosophers such as Descartes. How does mind make matter move? The new answer presented here draws from the physics behind the workings of those quantum computers. Where an “ordinary” computer can be thought of as operating through a series of switches that can be set to 0 or 1, the power of a quantum computer depends on the ability of quantum entities to be in two states at the same time, known as a superposition. So the switches in a quantum computer are both on and off (set at 0 and set at 1) at the same time. Building on ideas proposed by the Oxford physicist Roger Penrose, McFadden and Al-Khalili look at the quantum chemistry that just might be involved in conscious thought. “The scheme”, they say, “is certainly speculative, but it does at least provide a plausible link between the quantum and classical realms in the brain.” After all, if a plant can operate like a quantum computer in carrying out the process of photosynthesis, why couldn’t the human brain act as a quantum computer in carrying out the processes of thought? Given nature’s ability to make use of whatever is available, it would be surprising if it did not.
After that, almost anything would be an anticlimax – even a chapter discussing the puzzle of how life began. It would seem more natural to have this before the discussion of consciousness, since, after all, life began before it became conscious. But still, it is an important topic that could not be left out of a book such as this. For my (hopefully conscious) mind, though, this is the weakest section of the book, necessarily highly speculative, and not entirely convincing. There are clearly more questions than answers, but at least this means that there is plenty of work for the next generation of quantum biologists to do.
It may not be necessary, though to understand how life began to use an understanding of how life operates today at the quantum level to build completely artificial living organisms from the bottom up. Such a process would involve what the authors call “living technology” to manufacture from scratch organisms such as microbes which could produce antibiotics tailored to human requirements. This would be quite different from recent experiments with “artificial” life, which involve tinkering with DNA molecules, introducing them into already living cells, and persuading those cells to function in accordance with the instructions coded in the new DNA. This is inefficient because even after being “adapted” in this way, such modified cells continue to make lots of stuff that is of no use to us. The bottom up approach would result in what the authors describe as “a brave new world of quantum synthetic living organisms that could free their natural-born relatives from the drudgery of providing humanity with most of its needs.” A fine sentiment – unless, of course, those synthetic organisms turn out to be conscious.
Lifge on the Edge is a fascinating and thought-provoking book which manages to combine solid science, respectable extrapolation from the known into the unknown, and plausible speculation to give an accessible overview of a revolutionary transformation in our understanding of the living world. I will certainly look at robins with more respect in future.
John Gribbin is a Visiting Fellow in Astronomy
At the University of Sussex
And author of Computing with Quantum Cats: From Alan Turing to Teleportation