Evolutionary psychology is an approach to psychological science that explores the functions of human mind based on the Darwinian theory of evolution. From the Darwinian point of view, the existence of altruism is an enigma since such tendency reduces one’s own fitness while enhancing those of others. Any behavioral tendencies that lower one’s own fitness should be selected out from the population by the process of natural selection. Even so, there are many examples of altruistic behavior among human and non-human societies. There are two major theories that explain the evolution of altruistic behavior; theory of kin selection and theory of reciprocal altruism. I introduce the theories and empirical evidence that support them. At first glance, these lines of research may appear to argue about the psychological foundation of justice. However, it seems that the strength of “empirical evidence” are overestimated among non-specialists of empirical studies. I introduce the methodology of empirical approaches to psychology and explain their limitations. Specifically, I present that the relationship between statistical significance and sample sizes are prone to be looked over thus making fallible impression large effect sizes among the “audience” of empirical research. In addition, psychological science is currently facing the problem of failing replication or lack of replication of reported experiments. Given the power and limitation of evolutionary and empirical approaches to human mind and behavior, I discuss the feasibility of arguing psychological foundation of justice.
