The evolution of altruism poses a problem in evolutionary theory: How can natural selection favour individuals that carry altruistic traits over those carrying selfish traits?

This paper presents a simple framework that highlights the most fundamental requirement common to all competing theories for the evolution of altruism: sufficient assortment between carriers of helping traits and help from other individuals in the altruists' interaction environments. This requirement applies whether or not interacting individuals are related.

It thus challenges recent claims that relatedness is required for altruism and instead focuses attention on a unified understanding, based on assortment and interaction environments, of the biological mechanisms for the evolution of altruism.

Proceedings of the Royal Society B: Biological Sciences

Proceedings B is the Royal Society's flagship biological research journal, dedicated to the rapid publication and broad dissemination of high-quality research papers, reviews and comment and reply papers. The scope of journal is diverse and is especially strong in organismal biology.

Proceedings of the Royal Society B: Biological Sciences