An adaptation to favour related individuals to an organism, even at the expense of their own offspring. Altrusim in bees, ants, wasps, termites are classic examples

Often a mechanism that results in Cooperation behaviour

Example: Co-operation in eusocial hymenoptera

• Due to the haplodiploid nature, in a hive with one queen and one father:
  • The males are produced through parthinogenesis and have 100% of the same genes as the female
  • The females are $r=0.75$ to the queen since their father only gives one set of genes
• More complex:
  • Depends on sex ratio within colony
  • Has also evolved in diploid termites