Altruism

Definition

In behavioral ecology, behavior that increases the fitness of another individual at a cost to one's own direct fitness. Biological altruism is defined by fitness consequences rather than conscious intent; it encompasses acts that reduce personal survival or reproduction while benefiting others, and is often explained by kin selection, reciprocal altruism, or group selection. Distinguished from everyday moral altruism by its mechanistic, outcome-based definition.

Etymology

From French altruisme, coined by philosopher Auguste Comte from Italian altrui ('of or to others'), from Latin alter ('other').

Example

In honey bee colonies, worker bees perform suicidal stinging defense of the hive; the act kills the worker but protects genetically related nestmates, representing kin-selected altruism. Similarly, in some spider species, juveniles remain on the maternal web and forgo dispersal to assist in prey capture for siblings, reducing their own growth rate.

Synonyms

• other-regarding behavior
• self-sacrifice (in evolutionary context)

Related Terms

• Kin selection
• inclusive fitness
• reciprocal altruism
• eusociality
• selfish gene
• costly signaling
• cooperation
• social insect

Usage Notes

Biologists distinguish biological altruism (fitness outcome) from psychological altruism (motivational intent). The term is relative: a behavior is altruistic only when the cost exceeds the benefit to the actor, not merely when it benefits another. Some researchers reserve 'altruism' for costly acts between non-kin, using 'cooperation' or 'mutualism' for beneficial or neutral-sum interactions. In arthropod studies, apparent altruism often reveals cryptic selfishness upon closer examination, such as subordinate helpers in primitively eusocial wasps who may inherit the nest.