English: D. discoideum is a facultatively multicellular amoeba. When starved, single-celled amoebas aggregate into a slug-like multicellular body, then fruit. Fruiting body production requires the sacrifice of a minority of cells to produce a stalk. The potential for aggregation of multiple genotypes into a chimeric fruiting body gives opportunity to selfish ‘cheater’ genotypes (red), which benefit from but do not contribute to the stalks produced by other genotypes.