About 7 years ago, we initiated research into the evolutionary history of developmental signaling in the social amoebas, concentrating on cAMP signalling. A primary requisite for this project was the availability of a family tree that shows the relatedness of social amoeba species relative to the more ancestral solitary amoebazoans. We joined forces with the teams of Sandra Baldauf, an expert in protist molecular phylogeny, Thomas Winckler, who had already prepared an SSU rRNA tree of a subset of Dictyostelia species and two Dictyostelium field biologists, Jim Cavender and Hiromitso Hagiwara, to construct a molecular phylogeny of all known Dictyostelia. (24) We next mapped morphological traits of all species to the tree in order to determine the directionality of morphological evolution in the social amoebas. In parallel studies, the presence, regulation and function of genes that are essential for various aspects of cAMP signalling were investigated in social amoeba species that span the phylogeny. (25) This review presents a synthesis of the outcome of these studies with current insights in developmental signaling in the model species D. discoideum. It highlights major trends in the evolution of multicellular complexity in the social amoebas, and correlates these trends with elaboration of function of deeply conserved cAMP signalling genes.