Rediscovering Homo Sapiens in International Politics: Evolution and Rationality’s Missing Link

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ABSTRACT In How States Think, John Mearsheimer and Sebastian Rosato argue that the two dominant approaches to decision-making in international politics—rational choice theory and political psychology—are fundamentally flawed. Instead, they propose a model of rationality in which individuals use “credible theories” of how the world works to guide their assessments, and elites deliberate over these theories to determine foreign policy. I suggest that existing theory is too hastily rejected, and that these apparently opposing models can be reconciled by taking an evolutionary perspective—the process by which humans and human brains were built and therefore a critical, yet missing, part of the puzzle. An evolutionary perspective suggests: (1) rational choice is not always the most effective or efficient solution to decision-making problems; (2) cognitive biases are not mistakes, but adaptive “strategic instincts,” which evolved because they helped us make good decisions, not bad ones; (3) these “non-rational” dispositions follow a systematic pattern, allowing predictions about how people are likely to react under given conditions; (4) a theory for the origins of preferences; (5) an explanation for why humans can sometimes seem rational and sometimes non-rational (because adaptive behavior depends on context); and finally (6) error management theory suggests that cognitive biases evolved precisely because of uncertainty, as a way of minimizing costs over time. Human decision-making and behavior does not match the definition of either “rationality” or “non-rationality,” and is much better described as “adaptive rationality,” honed over the millennia to compete strategically for survival and reproduction under conditions of uncertainty.