The evolution of extraordinary self-sacrifice

Area of Science:

• Evolutionary Biology
• Behavioral Ecology
• Population Genetics

Background:

• Theoretical models predict individuals only sacrifice welfare if benefits outweigh costs.
• Extreme altruism and spite, involving significant costs like sterility or self-destruction, are observed in nature.
• Understanding the evolution of such extreme behaviors requires considering population structure and social interactions.

Purpose of the Study:

• To investigate the evolutionary conditions favoring "extraordinary" self-sacrifice in social behaviors.
• To determine how population structure and kin interactions influence the evolution of altruism and spite.
• To identify the specific ecological and genetic factors that permit extreme self-sacrificial behaviors.

Main Methods:

• Modeling the evolution of social behaviors in structured populations.
• Incorporating concepts of kin selection and local interactions.
• Analyzing scenarios involving actors and recipients with varying degrees of relatedness and dispersal patterns.

Main Results:

• Extraordinary self-sacrifice can evolve in structured populations where social actions provide secondary benefits to neighboring kin.
• Sedentary actors evolve extraordinary altruism towards dispersing kin when dispersal information is available.
• Sedentary actors evolve extraordinary spite towards sedentary nonkin when information on dispersal and kinship is provided.

Conclusions:

• Extraordinary self-sacrifice is facilitated by population structure that enhances benefits to related individuals.
• The evolution of extreme altruism and spite is contingent on the relatedness of neighbors to the actor and recipient.
• A key principle is that extreme self-sacrifice evolves when an actor's neighbors are close kin, and the recipient's neighbors are not.