“Biology’s next great horizon is to understand cells, tissues and organisms as agents with agendas” By Michael Levin & Daniel Dennett [Aeon]

“Cognition all the way down

Biology’s next great horizon is to understand cells, tissues and organisms as agents with agendas (even if unthinking ones)

Michael Levin

is the Vannevar Bush chair and Distinguished Professor of biology at Tufts University in Massachusetts, where he directs the Allen Discovery Center and the Tufts Center for Regenerative and Developmental Biology.

Daniel C Dennett

is the Austin B Fletcher professor of philosophy and co-director of the Center for Cognitive Studies at Tufts University. He is the author of more than a dozen books, the latest of which is From Bacteria to Bach and Back: The Evolution of Minds (2017). He lives in Massachusetts.



We think that this commendable scientific caution has gone too far, putting biologists into a straitjacket that prevents them from exploring the most promising hypotheses, just as behaviourism prevented psychologists from seeing how their subjects’ measurable behaviour could be interpreted as effects of hopes, beliefs, plans, fears, intentions, distractions and so forth. The witty philosopher Sidney Morgenbesser once asked B F Skinner: ‘You think we shouldn’t anthropomorphise people?’– and we’re saying that biologists should chill out and see the virtues of anthropomorphising all sorts of living things. After all, isn’t biology really a kind of reverse engineering of all the parts and processes of living things? Ever since the cybernetics advances of the 1940s and ’50s, engineers have had a robust, practical science of mechanisms with purpose and goal-directedness – without mysticism. We suggest that biologists catch up.


Recent advances in basal cognition and related sciences are showing us how to move past this kind of all-or-nothing thinking about the human animal – naturalising human capacities and swapping a naive binary distinction for a continuum of how much agency any system has.


 Treating cells like dumb bricks to be micromanaged is playing the game with our hands tied behind our backs and will lead to a ‘genomics winter’ if we stay exclusively at this molecular level. The lack of progress in rational morphogenetic control shows us this.


It has become standard practice to describe such phenomena with the help of anthropomorphic, intentional idioms: when we click the mouse, we tell the cursor to grab the thing on the screen, and as we move the mouse we move the thing on the screen until we signal to the cursor to drop the thing by clicking the mouse again. This talk of signalling and information-processing is now clearly demystified thanks to computers – no mysterious psychic powers here! – and this has been correctly seen to license use of such information talk everywhere in biology. Detectors and signals and feedback loops and decision-making processes are uncontroversial physical building blocks in biology today, just as they are in computers. But there is a difference that needs to be appreciated, since failure to recognise it is blocking the imagination of theorists. In a phrase that will need careful unpacking, individual cells are not just building blocks, like the basic parts of a ratchet or pump; they have extra competences that turn them into (unthinking) agents that, thanks to information they have on board, can assist in their own assembly into larger structures, and in other large-scale projects that they needn’t understand.

We members of Homo sapiens tend to take the gifts of engineering for granted. For thousands of years, our ancestors prospected for physical regularities that they could exploit by designing structures that could perform specific functions reliably. What makes a good rope, good glue, a good fire-igniter? The humble nut-and-bolt fastener is an elegantly designed exploitation of leverage, flexibility, tensile strength and friction, evolving over 2,000 years, and significantly refined in the past two centuries. Evolution by natural selection has been engaged in the same prospecting at the molecular level for billions of years, and among its discoveries are thousands of molecular tools for cells to use for specific jobs. Among those tools are antennas or hooks with which to exploit the laws of physics and computation.


Notice how ‘you’ can be a single cell or a multicellular organism – or an organ or tissue in a multicellular organism – and still be gifted with informational competences composed out of the basic ‘nuts and bolts’ of information-processing structures. Agents, in this carefully limited perspective, need not be conscious, need not understand, need not have minds, but they do need to be structured to exploit physical regularities that enable them to use information (following the laws of computation) to perform tasks, beginning with the fundamental task of self-preservation, which involves not just providing themselves with the energy needed to wield their tools, but the ability to adjust to their local environments in ways that advance their prospects.


The cooperation problem and the problem of the origin of unified minds embodied in a swarm (of cells, of ants, etc) are highly related. The key dynamic that evolution discovered is a special kind of communication allowing privileged access of agents to the same information pool, which in turn made it possible to scale selves. This kickstarted the continuum of increasing agency. This even has medical implications: preventing this physiological communication within the body – by shutting down gap junctions or simply inserting pieces of plastic between tissues – initiates cancer, a localised reversion to an ancient, unicellular state in which the boundary of the self is just the surface of a single cell and the rest of the body is just ‘environment’ from its perspective, to be exploited selfishly. And we now know that artificially forcing cells back into bioelectrical connection with their neighbours can normalise such cancer cells, pushing them back into the collective goal of tissue upkeep and maintenance.


This is a reasonable mechanistic story, but then isn’t all the talk of memory, decision-making, preferences and goal-driven behaviour just anthropomorphism? Many will want to maintain that real cognition is what brains do, and what happens in biochemistry only seems like it’s doing similar things. We propose an inversion of this familiar idea; the point is not to anthropomorphise morphogenesis – the point is to naturalise cognition. There is nothing magic that humans (or other smart animals) do that doesn’t have a phylogenetic history. Taking evolution seriously means asking what cognition looked like all the way back. Modern data in the field of basal cognition makes it impossible to maintain an artificial dichotomy of ‘real’ and ‘as-if’ cognition. There is one continuum along which all living systems (and many nonliving ones) can be placed, with respect to how much thinking they can do.

You have to remember that, while the most popular stories about how cells cooperate toward huge goals are about neural cells, there is little fundamental difference between neurons and other cell types. It is now known that synaptic proteins, ion channels and gap junctions, for instance, were already present in our unicellular ancestors, and were being used by electrically active cells to coordinate actions in anatomical morphospace (remodelling and development) long before they were co-opted to manage faster activity in 3D space. If you agree that there is some mechanism by which electrically active cells can represent past memories, future counterfactuals and large-scale goals, there is no reason why non-neural electric networks wouldn’t be doing a simplified version of the same thing to accomplish anatomical homeostasis. Phylogenetics has made it very clear that neurons evolved from far simpler cell types, and that some of the brain’s speed-optimised tricks were discovered around the time of bacterial biofilms (the biggest trick being scaling up into networks that can represent progressively bigger goal states and coordinating the Test-Operate-Test-Exit loop across tissues). Cognition has been a slow climb, not a magical leap, along this path.


From this perspective, we can visualise the tiny cognitive contribution of a single cell to the cognitive projects and talents of a lone human scout exploring new territory, but also to the scout’s tribe, which provided much education and support, thanks to language, and eventually to a team of scientists and other thinkers who pool their knowhow to explore, thanks to new tools, the whole cosmos and even the abstract spaces of mathematics, poetry and music. Instead of treating human ‘genius’ as a sort of black box made of magical smartstuff, we can reinterpret it as an explosive expansion of the bag of mechanical-but-cognitive tricks discovered by natural selection over billions of years. By distributing the intelligence over time – aeons of evolution, and years of learning and development, and milliseconds of computation – and space – not just smart brains and smart neurons but smart tissues and cells and proofreading enzymes and ribosomes – the mysteries of life can be unified in a single breathtaking vision.”

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