50 years of metaheuristics

In this paper, we review the milestones in the development of heuristic methods for optimization over the last 50 years. We propose a critical analysis of the main findings and contributions, mainly from a European perspective. Starting with the roots of the area that can be traced back to the classical philosophers, we follow the historical path of heuristics and metaheuristics in the field of operations research and list the main milestones, up to the latest proposals to hybridize metaheuristics with machine learning. We pay special attention to the theories that changed our way of thinking about problem solving, and to the role played by the European Journal of Operational Research in the development of these theories. Our approach emphasizes methodologies and their connections with related areas, which permits to identify potential lines of future research.