title: The evolution of cooperation based on direct fitness benefits.
authors.affiliation: Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland michael.taborsky@iee.unibe.ch.
authors.forename: Michael
authors.identifier: http://orcid.org/0000-0002-1357-4316
authors.initials: M
authors.lastname: Taborsky
authors.affiliation: Behavioural Ecology, Institute of Ecology and Evolution, University of Bern, Hinterkappelen, Switzerland.
authors.forename: Joachim G
authors.initials: JG
authors.lastname: Frommen
authors.affiliation: Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ, USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Riehl
mesh_terms: D000818:Animals; D005075:Biological Evolution; D003299:Cooperative Behavior; D056084:Genetic Fitness; D006801:Humans; D012641:Selection, Genetic
keywords: altruism; natural selection; non-kin cooperation; reciprocity; social evolution