Nature, the physicist
How quantum theory is helping to explain the mysteries of life science
Nov 22nd 2014 | From the print edition
Life on the Edge: The Coming of Age of Quantum Biology. By Jim Al-Khalili and Johnjoe McFadden. Bantam Press; 355 pages; £20. Buy from Amazon.com; Amazon.co.uk
LIFE science still hides a few mysteries. How do migratory birds sense direction? How are molecules in the air perceived as a smell? How, precisely, do tadpoles lose their tails? For years, scattered views from the fringes have attempted to explain such phenomena using quantum mechanics, a weird bit of physics that predicts oddities such as particles being in multiple places at once, eerily connected across vast distances or tunnelling through seemingly insuperable barriers.
Yet a growing body of experimental evidence suggests that quantum oddities may really be responsible for many of life’s engineering successes. Quantum biology, the name given to the nascent field that draws these diverse data together, is moving in from the fringes and becoming established. “Life on the Edge” is the first popular science book to outline it.
Quantum mechanics is one of science’s most successful theories, superseding Sir Isaac Newton’s “classical” physics, the workaday version taught at school. The theory’s weirder predictions—spooky connections, tunnelling and the like—are not part of people’s everyday experience. They happen at a microscopic level and, it was thought, only under precisely controlled conditions. Experiments were done by the steadiest hands in the darkest labs at the lowest achievable temperatures.
But life is nothing like that. Plants and animals are warmed and lit by the sun, mostly, and tend to be squidgy, moving and watery. It had long been assumed that a living being is a poor laboratory in which to carry out quantum experiments. But in 2007 scientists who were trying to understand how plants gather the sun’s energy so efficiently stumbled across something strange: that energy was sloshing around in what are called quantum coherences. In effect, the energy is in multiple places at the same time and “finds” the most efficient route from where it is collected to where it is put to use.
This first credible example inspired other scientists to follow similarly bold avenues of enquiry. To grasp these new threads in quantum biology is to grasp a quantity of quantum theory; the coherence is just one of the complex phenomena that Jim Al-Khalili and Johnjoe McFadden set out to teach the reader. They succeed by using delightfully revealing analogies and similes, some borrowed from their prior work, that make slippery concepts sit still for study.
The notion of “quantum entanglement” makes more sense when depicted as a pair of loaded dice. Molecules with left- and right-handed forms that vibrate in identical ways become left-handed Jimi Hendrix and right-handed Eric Clapton playing the same tune.
Once the quantum genie is out of the bottle, it is tempting to use it to explain all manner of phenomena. The book suggests that a molecule in birds’ eyes might be the site of a quantum effect that permits them to “see” a magnetic field and thereby to navigate. Subatomic particles tunnelling across gaps in the nose when aroma molecules are around may be the first step in how animals sense scent. This same tunnelling is presumed to be at work in the action of enzymes, those proteins that shuffle chemical reactions along in living things (among them, the breakdown of tadpoles’ tails as they become frogs).
Some of the ideas presented are quite speculative. Quantum weirdness, after all, has long been used to excuse all sorts of questionable science. In 1989 Roger Penrose, an Oxford mathematician, proposed a quantum mechanism for consciousness that was met with deep scepticism. Yet Messrs Al-Khalili and McFadden go on to revise Mr Penrose’s theory in light of more recent experiments. Where doubt remains, work continues. The authors themselves are leading the search for a quantum mechanism in genetic mutations, which might be giving evolution itself a helping hand.
That quantum effects are an incontrovertible part of some of life’s machinery is reason enough to go looking for more examples. The ideas in “Life on the Edge” may be dead ends, or they may be just the beginning. Either way, the quantum telescope is set on far horizons.
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