What Is Kin Selection?

Kin selection is an evolutionary strategy where an organism increases its overall genetic success by helping relatives—who share many of its genes—reproduce, even if it means sacrificing its own chances of direct reproduction. The theory, first formalized by W.D. Hamilton, explains the evolution of altruistic behaviors, such as when animals risk their own safety or resources to assist siblings, offspring, or other close kin.

How Kin Selection Works

• Genetic Relatedness: The closer the genetic relationship, the more likely an individual is to help. For example, helping a sibling (who shares about 50% of genes) can be nearly as valuable, genetically, as producing one’s own offspring.

• Altruism Explained: Acts that seem selfless—like sterile worker bees caring for the queen’s young—are favored by kin selection because they boost the reproductive output of relatives, thereby increasing the helper’s indirect genetic contribution to future generations.

• Hamilton’s Rule: Altruistic behavior evolves when the genetic benefit to relatives, weighted by relatedness, exceeds the cost to the individual.

Kin Selection vs. Inclusive Fitness

• Inclusive fitness is the broader concept, encompassing both direct fitness (from one’s own offspring) and indirect fitness (from helping relatives).

• Kin selection specifically refers to the process by which natural selection favors behaviors that increase the reproductive success of relatives due to shared genes.

Real-World Examples

• Meerkats standing guard: Individuals risk their lives to warn relatives of predators.

• Worker ants and bees: Forfeit their own reproduction to help the queen, their mother, produce more siblings.

• Birds feeding siblings: Sometimes older chicks help feed younger ones, increasing the survival of shared genes.

Why Kin Selection Is the Correct Term

While “inclusive fitness” describes the total genetic contribution, the process by which animals help relatives to increase their genetic representation in the next generation is called kin selection. This concept is now central to understanding social behavior, cooperation, and the evolution of altruism in the animal kingdom.

Correct answer: (4) Kin selection