Hamilton's rule is a principle in evolutionary biology that explains how altruistic behaviors can evolve among related individuals. It states that an altruistic act is favored by natural selection if the genetic relatedness between the altruist and the recipient, multiplied by the benefit received by the recipient, exceeds the cost to the altruist. This can be expressed mathematically as rB > C, where r is the genetic relatedness, B is the benefit to the recipient, and C is the cost to the altruist. The rule highlights the importance of kinship in social behaviors, suggesting that individuals are more likely to help those who share their genes. This concept helps explain phenomena such as cooperative breeding in species like honeybees and naked mole rats, where individuals assist relatives in raising offspring, thereby increasing their own indirect fitness.