The identification of shared genes and derived characteristics among distantly related organisms helps us to understand how cells and tissues are organized and how this organization evolved. Dickinson et al. have discovered that unicellular organisms capable of social organization, such as the amoeba Dictyostelium discoideum, can differentiate cells into simple tissues. Dictyostelium epithelium is composed of a single layer of elongated polarized cells necessary for the formation of the fruiting body. The organization, morphology, and function of Dictyostelium epithelium are dependent on an ancestral signaling pathway that is composed of the functional orthologs of α- and β-catenins but that does not require Wnt signaling or cadherins.