Can evolution explain free will?

December 11th 2023

Neuroscientist Kevin J Mitchell explains how evolution gave us and other organisms the power to shape our futures

It seems trendy these days to declare: “free will is an illusion”. We may feel like we’re in charge, like we – our selves – are capable of making deliberative decisions and choosing our own actions for our own reasons. However, science has proven otherwise, or so the claim goes.

Behavioural genetics has revealed how we come with innate individual natures – sets of psychological predispositions and behavioural tendencies that we did not choose ourselves¹. Furthermore, reports from experimental psychology are constantly telling us how our actions are affected by subconscious factors – hidden layers of our psyche and subtle influences from our surroundings. 

Even sterner challenges come from neuroscience. The incredible progress being made in elucidating neural circuits, and systems underlying various behaviours or cognitive operations, can leave the impression that it is all just complicated electrochemical mechanisms. That, as Francis Crick once claimed, our conscious experiences, our sense of personal identity and free will are “no more than the behaviour of a vast assembly of nerve cells and their associated molecules”².

And, if we’re going down levels, why stop there? Those molecules are made of atoms and particles that must obey the laws of physics. Any physical system will evolve from moment to moment in an inexorable way, fully determined by the low-level instantaneous properties of all those particles.

If this were true, we’d really be in trouble. We might not be at all, in fact. There would be no doings in such a universe, merely inevitable happenings. No normal counterfactual sense of causation; no differences to make a difference.

An open future

Fortunately for life, the universe does not seem to follow this strictly deterministic trajectory, where only one future is possible and a single timeline could be projected in advance, from the Big Bang to the point of me writing this sentence and you reading it.

Quite the opposite: the probabilistic nature of the resolution of quantum indeterminacies and the finite information available in the physical universe at any moment mean that the future is radically open (or at least that is a viable interpretation³). The instantaneous low-level details of a system and the laws of physics do not comprehensively determine its subsequent states.

This allows two crucial factors to come into play: organisation and history. The way a system is organised can be an additional causal factor in how the system evolves through time. Not by violating or overriding the laws of physics governing how forces play out, but by constraining the components of a system in ways that shape how they behave4. That is a pretty good description of life.

Living systems are organised sets of processes that constrain each other in such a way as to persist through time, doing work to remain out of equilibrium with their environment5. Here, the organisation is for something – purpose arises for the first time. Because variations will arise in this indeterministic universe, selection will inevitably act, favouring the persistence of those organisations that are, well… good at persisting. 

This is what life is: self-organised systems that are trying to stay that way. For most organisms this means constantly adapting and reconfiguring their metabolism and physiology to accommodate to changing conditions. Selection ensures that organisms have the tools to help them do that6. One good trick, when faced with a dynamic world, is to be able to move around in it or act on it to find or make more favourable conditions. To do this adaptively requires motors and actuators but also requires sensors and some kind of internal control systems. The organism must be able to figure out what is out in the world and what to do about it.

Evolution of agents

Something new came into the world: agents – living systems organised with functional capacities that enable them to act for reasons, to constrain their own components in ways that adaptively constrain the possibility space of the world around them. To make happen what they want to happen. Not just in momentary responses to isolated stimuli, but in a proactive, integrative, holistic and sustained way through time7.

With the evolution of nervous systems, these control systems became more and more elaborate, letting animals learn from experience and accumulate knowledge of the world – causal potential to guide adaptive action8. They literally incorporate this information into the configuration of their nervous systems, developing more complex models of themselves and of the world. The increasing depth and sophistication of these models in animals with complex brains allows prediction over longer timeframes and more complex scenarios.

One final step sets humans apart. We can reason about our reasons. The extra levels of our cognitive hierarchies let us make models of our own minds. We can recursively think about our beliefs and desires and intentions, and consciously operate on them as objects of cognition, not just elements of it. We can consider and decide, and reconsider, and change our minds – we can consciously deliberate and choose our actions.

It’s not absolutely free from any prior causes, as some people seem to demand of ‘free will’. On the contrary, our actions are informed by our past and directed towards our future. That is precisely what allows us to persist as selves through time. We have degrees of freedom and we exert our will to choose among them.

Free Agents: How Evolution Gave Us Free Will by Kevin J Mitchell is out now via Princeton Publishing

Kevin J Mitchell is Associate Professor of Genetics and Neuroscience at Trinity College Dublin, and author of Free Agents: How Evolution Gave Us Free Will 


1) Mitchell, K. J. Innate: How the Wiring of Our Brains Shapes Who We Are (Princeton University Press, 2018).

2) Crick, F. The Astonishing Hypothesis: The Scientific Search for the Soul (Scribner, 1994).

3) del Santo, F. & Gisin, N. Physics without determinism: Alternative interpretations of classical physics. Phys. Rev. A 100, 062107 (2019).

4) Juarrero, A. Context Changes Everything: How Constraints Create Coherence (MIT Press, 2023).

5) Maturana, H. R. & Varela, F. J. Autopoiesis and Cognition (D. Reidel Publishing Company, 1980).

6) Ellis, G. F. R. On the nature of causation in complex systems. Trans. R. Soc. South Africa 63, 69–84 (2008).

7) Potter, H. D. & Mitchell, K. J. Naturalising agent causation. Entropy 24, 472 (2022).

8) Mitchell, K. J. Free Agents: How Evolution Gave Us Free Will (Princeton University Press, 2023).