This document reviews hominin taxonomy and systematics. It presents two taxonomic hypotheses that recognize either more species (a "splitting" taxonomy) or fewer, more inclusive species (a "lumping" taxonomy). The taxa are grouped into grades based on inferred behaviors and adaptations rather than evolutionary relationships. The splitting taxonomy recognizes several possible early hominin taxa in addition to Ardipithecus ramidus, as well as multiple species of Australopithecus, Paranthropus, Homo, and anatomically modern humans. Issues of distinguishing early hominins from early panins and criteria for recognizing hominin genera and species are also discussed.