Evolution of Cooperation

Cooperation

Helping others; costly to actor but beneficial to recipient.

Tragedy of the commons

Cheaters exploit cooperators; cooperation unstable.

Inclusive fitness

Direct + indirect fitness via relatives.

Kin selection

Helping relatives increases gene transmission; rb > c.

Hamilton's rule

Altruism evolves when rb - c > 0.

Coefficient of relatedness (r)

Probability alleles are identical by descent.

Examples of r

Parent/child = 0.5; siblings = 0.5; aunt-niece = 0.25; cousins = 0.125.

Reciprocity

Cooperation maintained via repeated interactions with cooperators.

Partner choice

Preferentially helping known cooperators; punishing cheaters.

Fitness alignment

Conditions align interests so cooperation benefits both parties.

Green beard effect

Trait + recognition + helping linked; cheats identifiable.

Spatial structure

Local interactions allow cooperators to cluster and prosper.

Group selection (modern)

Patches with more cooperators outperform others.