Hamilton's rule and the causes of social evolution

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Genetics

Background:

• Inclusive fitness theory, also known as kin selection, explains the evolution of social behavior.
• Hamilton's rule is a foundational theorem within this theory, outlining conditions for altruism.
• Social behavior is observed across diverse taxa, including insects, birds, and mammals.

Purpose of the Study:

• To review and synthesize evidence supporting Hamilton's rule.
• To examine empirical studies parametrizing Hamilton's rule in natural populations.
• To analyze comparative phylogenetic studies on the correlates of sociality.

Main Methods:

• Empirical parametrization of Hamilton's rule in natural populations.
• Comparative phylogenetic analyses of genetic, life-history, and ecological factors.
• Meta-analysis of studies on cooperative breeding and eusociality.

Main Results:

• Altruism is observed even in facultative sociality and is selected for via indirect fitness benefits exceeding direct costs.
• Social behavior enhances kin productivity and survivorship, generating indirect benefits.
• High relatedness, monogamy, facilitating life-history traits, and low ecological costs promote sociality.

Conclusions:

• Empirical and phylogenetic studies strongly support Hamilton's rule.
• The findings confirm the predicted conditions and underlying causes for the evolution of social behavior.
• Hamilton's rule provides a robust framework for understanding kin selection and social evolution.