The evolution of mutually exclusive alternatives

Decision making is a fundamental aspect of cognition that lies at the heart of theories about behaviour, learning, and mental processing. It spans multiple levels of complexity, from high-level planning to low-level movement control and perceptual recognition. Tracking the evolutionary trajectory of this elementary cognitive process can illuminate the foundations of behaviour and brain functions. This paper highlights a previously understudied defining feature of decision mechanisms: the ways in which mutual exclusion between alternatives is achieved. We argue that any decision is defined by a set of mutually exclusive alternatives, and this exclusivity – rather than the specific identity of the alternatives – requires specialized mechanisms. We demonstrate how the physical body of simple decision-making entities can serve as such a mechanism, and that the detachment of these mechanisms from bodily and environmental constraints enabled complex decision-making. Furthermore, while many theories emphasize how the evolution of neural circuits enhanced integration and control through associative structures, we propose that the evolution of mutual exclusion requires non-associative constructions. We conclude that understanding the evolution of these mechanisms is crucial for studying cognitive evolution, and we propose a potential evolutionary trajectory.