Abstract: Inclusive fitness theory was one of the most important theories of evolutionary biology and evolutionary psychology. From the perspective of that theory, the relatives had different value of fitness. Asymmetric kin altruism had been found in several areas, for example, maternal grandmothers always invest the most to their grandsons (granddaughters), followed by maternal grandfathers, then paternal grandmothers, with paternal grandfathers investing the least. Inclusive fitness theory and some specific evolutionary hypotheses such as paternity uncertainty hypotheses could be used to explain that phenomenon. Moreover, we described three of the most commonly recurring misunderstandings of inclusive fitness. Finally, we believed it would be better if researchers in the future could pay more attention to asymmetric kin altruism, try to define altruism behaviors with the same indicators, and collect data using different methods.

Key words: evolutionary psychology, inclusive fitness theory, asymmetric kin altruism, kin investment, paternity uncertainty, mating opportunity costs