The evolutionary puzzle of cognition: challenges and insights from individual-based studies.

Cognition is widely believed to confer adaptive benefits, yet empirically demonstrating these benefits and understanding their evolutionary origin remains a significant challenge. Individual-based studies in the wild are essential for demonstrating that a cognitive trait is an adaptation. However, such approaches have so far yielded only partial evidence for the adaptive significance of cognition. Building on previous research, we highlight key challenges of individual-based studies that remain underappreciated and warrant further attention. These include the need for precise characterization of functionally relevant cognitive traits, a deeper understanding of heritable variation, more robust assessments of key fitness components across large cohorts and extended timescales, and clearer identification of the fitness benefits and selective pressures involved. We discuss how the lack of such comprehensive information limits our ability to fully evaluate how cognitive traits affect fitness, and to explore their demographic and evolutionary consequences. To bridge the gap between micro- and macroevolutionary processes, we also emphasize the need to better integrate individual-based research with broader population and species comparative analyses. By refining and expanding the approach, individual-based studies can deepen our insight into the evolutionary forces that have given rise to the remarkable diversity of minds across the animal kingdom.This article is part of the Theo Murphy meeting issue 'Selection shapes diverse animal minds'.