Science and art can look like conceptually separate worlds. But music can teach us a lot about our scientific blind spots and offer new ways of framing complex problems. Biologist Denis Noble and Computer Scientist turned evolutionary theorist Richard Watson set out a musical vision of life, and why it offers a powerful and detailed metaphor for the life sciences.

Since Pythagoras’ music of the celestial spheres, music has been a particularly strong bridge between science and art because of its mathematical underpinnings, its geometric aesthetics and its visceral ability to reach our emotions. Indeed, music was held in affinity with cosmic beauty and meaning long before the ancient Greeks.

Much like Johannes Kepler and Michio Kaku, Denis Noble’s approach to biology has freely employed musical metaphors as a framework with which to approach the world. In The Music of Life (2006) and Dance to the Tune of Life (2016), he has represented genes as comparable to the score of a piece of music, whereas life itself is more like the live playing of the piece in which organisms orchestrate the activity of their genes. In doing so, science is able to reach beyond itself, to transcend purely descriptive empirical statements. It is through music that metaphor and scientific reasoning come together to broaden our understanding and perception of the universe.

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In being part of a living composition, life perhaps takes on a bit more meaning.

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When considering biology from a systems theory perspective, music becomes a particularly useful scientific metaphor. There are many facets to the analogy between music and living things, from orchestration, to 'aliveness' and harmony. In being part of a living composition, life perhaps takes on a bit more meaning. But any implication that the evolution of life is unfolding according to a certain theme or plan is vehemently denied by scientific perspectives.

Considering life as an unfolding musical composition isn’t wishful thinking produced by our delusory need for a sense of purpose. Without invoking anything supernatural, there is something missing and desperately needed in the biological sciences, not to mention our personal lived experience. The current biological account of causation is limited, and limits our understanding. By thinking about music and harmony, we are able to access a more developed account of causation that better explains living organisms.

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Specifically, it is kind of an open secret in biology that there is a very poor understanding of the link between how tiny parts function at the micro-scale (e.g. gene products, organic molecules, intracellular structures, and so on) and how organisms as a whole (perhaps containing trillions of cells) develop and behave as coherent purposeful agents. This is the link between conventional ‘bottom-up’ (reductive/molecular) causation and ‘top-down’ (organisational) causation, and it is a link that is already familiar in musical principles.

Consider what determines the note that is played when we pluck a guitar string. The microscopic properties of the steel — its mass, the spring constant and temperature — are all involved. But the note the string plays is also determined by the geometry of the string as a whole, its length or where it is fretted. How the two interact is rather telling. The initial impulse creates a ’kink’ that travels as a collection of waves of many frequencies up and down the length of the string, at speeds determined by the string’s micro-scale properties. But this is not yet a note — just disorganised energy in the string. These waves reflect at either end of the string to meet themselves coming back in the other direction. The timing of the reflections is determined by the length of the string as a whole — which wavelengths fit neatly and build-up, and which cancel-out. In the resonant standing wave that results, and its overtones, it is the geometry of the string as a whole, not just the individual properties of the molecules it contains, that determines whether the frequency of that note is a G or an E.

Beyond the physics, to larger organisational scales, the two directions of causation continue in the musical context; a piece of music contains individual notes, but the structure of the music as a whole determines which notes are a possible fit for each moment. Otherwise, a note could never be out of tune or late.  The sense of ‘wrongness’ we might feel in a piece is not a matter of faithfulness to a score; it results from the lack of harmonic fit and resonant relationships afforded by the context.

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Resonance, phase-locking, beating, harmonic ratios, and many other concepts further deepen the link between upward and downward causation in living systems.

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In living systems, this is self-correcting. The expression of a gene or a particular epigenetic state of a cell can be pulled into existence when it is needed by the resonant context of the whole — a note summoned by the music in the moment, not pre-specified by genetic instructions.  For example, whether a stem cell develops into bone, or skin or part of your liver is not determined by its genes but by the electrical and chemical signalling it receives from neighbouring cells as they mutually determine who will play what role in the body. And at smaller scales, although the DNA sequence that codes for a particular gene is generally fixed, the behaviour of the proteins they produce is not. As many as 50% of your proteins can be folded in different ways in different contexts. For example, the protein aconitase can either catalyse a step in the Krebs Cycle or, depending on its environment, fold differently to act as an RNA binding protein that regulates iron intake. It thus serves entirely different functions as needed, at fast timescales, without any change to the DNA.

This analogy is not superficial. Formally, the two directions of causation do not and cannot happen in sequence. It is evident from the mathematics involved that they are not competing for the same causal space. Downward causation sets the boundary and initial conditions (what Aristotle called the formal causes) that enable any specific solution to be produced. Upward causation determines the mechanics of the interactions at a lower level given these boundaries and conditions (Aristotle called these mechanics the efficient cause).

When we integrate the differential equations involved, both forms of causation are necessarily incorporated at the same time. A purely reductionist interpretation of biology hopes to manage using only the latter kind, but a comprehensive theory of biology needs to respect the two-way interaction between causes at different levels of organization. This is not just a technicality nor an esoteric philosophical matter. The difference between a normal and healthy pattern of rhythmic activity in your heart and a pattern of fibrillation that is lethal is not found in any amount of molecular or genetic scrutiny of the parts but in the resonant dynamics of the whole.  Normal rhythm is co-ordinated at the level of the whole heart and is an ordered progression of electric excitation from the pacemaker to all other parts of the heart as a single spreading wave. Disordered rhythm occurs when one wave automatically seeds further waves competing with each other in a chaotic fashion, thus generating the lethal ventricular fibrillation. This behaviour only makes sense in the heart as a whole.

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When we see the resulting dynamics of any particular system in any particular instance, it is always possible to enumerate the positions and conditions of all of the parts, and their microscopic relations as we find them in this configuration, and tempting to conclude that we have identified the causes. We might think that the string plays a G because each molecule involved is pulling and pushing on its neighbours, as the microscopic physical laws dictate, and in this configuration, that’s what they must do — nothing more to it! But it is also true that without reference to the organization of the whole, and the resonant dynamics between the two, the physical laws do not dictate why the microscopic parts were in that configuration and not some other.

Resonance, phase-locking, beating, harmonic ratios, and many other concepts further deepen the link between upward and downward causation in living systems. For example, in sound and vibration, beating occurs when two notes are not quite the same frequency, producing periodic surges in amplitude as the oscillations come in and out of phase. The same principle is found in the morphogenetic mechanisms that produce segmented body plans, as morphogens with wavelengths that are not quite the same travel along the body.

One is therefore tempted to say that it is not just a metaphor. Life and music, like other links between the sciences and the arts, have an ancient and enduring relationship for sound reasons – pun intended.