An article published in the journal “PLOS Biology” reports an analysis of the information available on the relationships among mammal species that aims to build an evolutionary family tree of this group of animals. Nathan Upham and Walter Jetz of Yale University together with Jacob Esselstyn of Louisiana State University used data on fossils and genomics to try to analyze at phylogenetic level the evolution of the various branches within the mammal taxonomic class. Understanding their relationships offers information on their history and biodiversity, a crucial step for environmental conservation.