What distinguishes inclusive fitness from direct fitness?

Inclusive fitness encompasses not only an individual's own reproductive success but also the reproductive success of its close relatives. This broader consideration of fitness allows for the understanding of how behaviors that may not directly benefit the individual can still promote the survival and reproduction of shared genetic material in relatives. For example, when an animal helps raise the offspring of its siblings, it enhances the survival prospects of relatives and thereby contributes to inclusive fitness.

In contrast, direct fitness is strictly about an individual’s own offspring and reproductive success without accounting for any benefits gained by aiding relatives. Although direct fitness may contribute to overall fitness in terms of passing on genes, it does not capture the full spectrum of genetic contribution that inclusive fitness does, as inclusive fitness emphasizes the importance of social behaviors and kin selection.