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, 100 (13), 7684-9

Genera of the Human Lineage


Genera of the Human Lineage

Camilo J Cela-Conde et al. Proc Natl Acad Sci U S A.

Erratum in

  • Proc Natl Acad Sci U S A. 2003 Aug 19;100(17):10133-5


Human fossils dated between 3.5 and nearly 7 million years old discovered during the last 8 years have been assigned to as many as four new genera of the family Hominidae: Ardipithecus, Orrorin, Kenyanthropus, and Sahelanthropus. These specimens are described as having morphological traits that justify placing them in the family Hominidae while creating a new genus for the classification of each. The discovery of these fossils pushed backward by >2 million years the date of the oldest hominids known. Only two or three hominid genera, Australopithecus, Paranthropus, and Homo, had been previously accepted, with Paranthropus considered a subgenus of Australopithecus by some authors. Two questions arise from the classification of the newly discovered fossils: (i) Should each one of these specimens be placed in the family Hominidae? (ii) Are these specimens sufficiently distinct to justify the creation of four new genera? The answers depend, in turn, on the concepts of what is a hominid and how the genus category is defined. These specimens seem to possess a sufficient number of morphological traits to be placed in the Hominidae. However, the nature of the morphological evidence and the adaptation-rooted concept of what a genus is do not justify the establishment of four new genera. We propose a classification that includes four well defined genera: Praeanthropus, Ardipithecus, Australopithecus, and Homo, plus one tentative incertae sedis genus: Sahelanthropus.


Fig. 1.
Fig. 1.
Phylogeny of the genera belonging to the Hominid family. Four different genera are proposed, corresponding to four kinds of adaptation. The genus Praeanthropus (formerly named Australopithecus) evolved incipient bipedalism on the ground of tropical forests. The genus Ardipithecus evolved a dietary adaptation that developed thin molar enamel, similar to that of the African great apes. The genus Australopithecus (formerly also named Paranthropus) exploited hard vegetal resources of the savanna by developing a robust masticatory apparatus. The genus Homo retained gracile maxillae and dentition and later initiated the development of larger crania and cultural adaptation to the savanna by means of lithic industries. The proposed names follow the rules of taxonomy, favoring the names given initially, when the first taxon of the genus was established. The phylogenetic location and taxonomic classification of Sahelanthropus are uncertain. Pairs of Homo taxa separated by a slash represent closely related (or, according to some authors, the same) species. An asterisk marks each species germinalis, i.e., originating a genus.

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