the JASs is published by the Istituto Italiano di Antropologia www.isita-org.com Ethics and Altruism Altruism in humans: an evolutionary approach

Altruism was originally defi ned as a co-operative act infl icting a cost to the donor and only giving a benefi t to the recipient. However, no study has ever conclusively demonstrated the existence of altruistic behaviours that do not give any short- or long-term benefi ts to donors. Th erefore, the term altruism is generally used for costly behaviours that may potentially also be benefi cial for the donor. In accordance with this broader defi nition, two main concepts have been traditionally proposed to explain the evolution of altruism: inclusive fi tness (Hamilton, 1964) and reciprocal altruism (Trivers, 1971). Altruism among kin evolves through kin selection (Hamilton, 1964), a