This review summarizes the recent construction of a systematic framework to study causal relationships between genotypic and phenotypic change during evolution of the social amoebas. The foundation of this framework is the first DNAbased phylogeny for all known species of social amoebas. The phylogeny, which is based on SSU rDNA sequences and confirmed by a-tubulin protein sequences shows subdivision into four major groups and a molecular depth that is equal to that of all animals. (24) A plotting of the most consistently noted species characters onto the phylogeny shows unexpected trends in character evolution with the greatest changes occurring at the transition between the youngest group 4 and the evolutionary older groups 1,2 and 3. Group 4 species are characterized by large solitary and unbranched fruiting structures as opposed to smaller, clustered and branched structures in the other groups. Group 4 species have also lost the ancestral survival strategy of encystation and gained the use of cAMP as chemotactic signal for aggregation.