Hamilton’s rule

Hamilton’s rule states that r > c/b, where r is the relatedness, c the costs and b the benefits.
It shows, in any society, to what extent living organisms are naturally willing to make exceptions and sacrifices in order to help others.
Relatedness can be purely genetic (percentage of shared genes), for the survival of the group or the species, or have something to do with intellectual kinship – what Goethe called “Les Affinités Electives” – in more complex individuals.