Arto Annila

To explain why cognition evolved requires, first and foremost, an analysis of what qualifies as an explanation. In terms of physics, causes are forces and consequences are changes in states of substance. Accordingly, any sequence of events, from photon absorption to focused awareness, chemical reactions to collective behavior, or from neuronal avalanches to niche adaptation, is understood as an evolution from one state to another toward thermodynamic balance where all forces finally tally each other. From this scale-free physics perspective, energy flows through those means and mechanisms, as if naturally selecting them, that bring about balance in the least time. Then, cognitive machinery is also understood to have emerged from the universal drive toward a free energy minimum, equivalent to an entropy maximum. The least-time nature of thermodynamic processes results in the ubiquitous patterns in data, also characteristic of cognitive processes, i.e., skewed distributions that accumulate sigmoidally and, therefore, follow mostly power laws. In this vein, thermodynamics derived from the statistical physics of open systems explains how evolution led to cognition and provides insight, for instance, into cognitive ease, biases, dissonance, development, plasticity, and subjectivity.

Many mechanisms, functions and structures of life have been unraveled. However, the fundamental driving force that propelled chemical evolution and led to life has remained obscure. The second law of thermodynamics, written as an equation of motion, reveals that elemental abiotic matter evolves from the equilibrium via chemical reactions that couple to external energy towards complex biotic non-equilibrium systems. Each time a new mechanism of energy transduction emerges, e.g., by random variation in syntheses, evolution prompts by punctuation and settles to a stasis when the accessed free energy has been consumed. The evolutionary course towards an increasingly larger energy transduction system accumulates a diversity of energy transduction mechanisms, i.e. species. The rate of entropy increase is identified as the fitness criterion among the diverse mechanisms, which places the theory of evolution by natural selection on the fundamental thermodynamic principle with no demarcation line between inanimate and animate.

The concept of time is examined using the second law of thermodynamics that was recently formulated as an equation of motion. According to the statistical notion of increasing entropy, flows of energy diminish differences between energy densities that form space. The flow of energy is identified with the flow of time. The non-Euclidean energy landscape, i.e. the curved space–time, is in evolution when energy is flowing down along gradients and levelling the density differences. The flows along the steepest descents, i.e. geodesics are obtained from the principle of least action for mechanics, electrodynamics and quantum mechanics. The arrow of time, associated with the expansion of the Universe, identifies with grand dispersal of energy when high-energy densities transform by various mechanisms to lower densities in energy and eventually to ever-diluting electromagnetic radiation. Likewise, time in a quantum system takes an increment forwards in the detection-associated dissipative transformation when the stationary-state system begins to evolve pictured as the wave function collapse. The energy dispersal is understood to underlie causality so that an energy gradient is a cause and the resulting energy flow is an effect. The account on causality by the concepts of physics does not imply determinism; on the contrary, evolution of space–time as a causal chain of events is non-deterministic.

Life is supported by a myriad of chemical reactions. To describe the overall process we have formulated entropy for an open system undergoing chemical reactions. The entropy formula allows us to recognize various ways for the system to move towards more probable states. These correspond to the basic processes of life i.e. proliferation, differentiation, expansion, energy intake, adaptation and maturation. We propose that the rate of entropy production by various mechanisms is the fitness criterion of natural selection. The quest for more probable states results in organization of matter in functional hierarchies.