Hamilton's Rule is a fundamental concept in evolutionary biology that explains the conditions under which altruistic behavior can evolve. It is often expressed as an equation: rB > c, where:
- r represents the coefficient of relatedness between the altruistic individual and the recipient of the altruistic act.
- b represents the benefit to the recipient.
- c represents the cost to the altruistic individual.
The rule states that altruism is favored by natural selection when the benefit to the recipient, weighted by their degree of relatedness to the altruist, outweighs the cost to the altruist.
Applications of Hamilton's Rule
Hamilton's Rule has been applied to explain a wide range of altruistic behaviors in nature, including:
- Kin selection: Individuals are more likely to help close relatives, as they share a higher proportion of their genes. For example, alarm calls in ground squirrels warn relatives of danger, even at the cost of increased predation risk for the caller.
- Eusociality: In eusocial insects like ants and bees, individuals often forego reproduction to help their queen raise offspring. This behavior is explained by the fact that workers are closely related to the queen and her offspring.
- Reciprocal altruism: Individuals may help unrelated individuals if they expect to be helped in return. This is often seen in cooperative breeding systems, where individuals help raise young that are not their own.
Practical Insights
Hamilton's Rule provides a powerful framework for understanding the evolution of altruism. It highlights the importance of kinship in promoting cooperation and the potential for reciprocal altruism to evolve in unrelated individuals.
Examples
- Vampire bats: Vampire bats often share blood meals with unrelated individuals who have failed to find a meal. This behavior is likely driven by the expectation of reciprocal altruism.
- Chimpanzees: Chimpanzees will often groom each other, which is a form of altruism. This behavior may be driven by kin selection, as chimpanzees are more likely to groom close relatives.
