Hominini is the tribe of Homininae that comprises Homo, and the two species of the genus Pan (the Common Chimpanzee and the Bonobo), their ancestors, and the extinct lineages of their common ancestor (but see the discussion below for alternative views). Members of the tribe are called hominins (cf. Hominidae, "hominids"). The subtribe Hominina is the "human" branch, including genus Homo and its close relatives, but not Pan. All species in this tribe carry the same four blood types which can be exchanged between species.
The creation of this taxon is the result of the current idea that the least similar species of a trichotomy should be separated from the other two. Through DNA comparison, scientists believe the Pan/Homo divergence occurred between 5.4 and 6.3 million years ago, after an unusual process of speciation that ranged over 4 million years. Few fossil specimens on the Pan side of the split have been found, the first fossil chimpanzee discovery being published in 2005, dating to between 545 ± 3 kyr (thousand years) and 284 ± 12 kyr via 40Ar/39Ar, from Kenya's East African Rift Valley. All of the extinct genera listed in the table to the right are ancestral to Homo, or are offshoots of such. However, both Orrorin and Sahelanthropus existed around the time of the split, and so may be ancestral to all three extant species.
In the proposal of Mann and Weiss (1996), the tribe Hominini includes Pan as well as Homo, but as separate subtribes. Homo (and, by inference, all bipedal apes) is in the subtribe Hominina, while Pan is in the subtribe Panina. However, there are alternative definitions: some researchers use the term Hominini to include humans and fossil ancestors, but not chimpanzees. Wood (2010) discusses the different views of this taxonomy.