Cooperation and conflict in evolutionary biology

Natural selection primarily acts at the level of the individual. Despite this, cooperation exists in all species and at levels of biological organisation. In contrast to cooperation, conflict is also common, and the same mechanisms that resolve conflicts between individuals also promote cooperation. Explaining cooperation once presented a major challenge in evolutionary biology, but the general conditions under which cooperation can evolve are now well understood. As long as an individual has a net gain in its inclusive fitness (that is, its own direct fitness, plus its indirect fitness, through genetically related kin) from a given behaviour, that behaviour will be able to increase in frequency. These benefits can be either direct, or indirect. This thesis examines the conditions under which cooperation and conflict (and the resolution of conflict can evolve). The first part looks at the tragedy of the commons in evolutionary biology, with a particular focus on tragedies involving sexual reproduction. The second part examines the evolution of cooperation, with a focus on game theoretical models, while the third investigates cooperation and conflict in the bacterial genome. The thesis is primarily theoretical, but with a focus on different biological systems. Cooperation lies at the heart of biological organisation, and all systems are prone to conflict. This thesis highlights some of the ways in which conflict can be resolved, and the mechanisms under which cooperation can evolve in a diverse range of biological systems