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Underestimating intraspecific variation: The problem with excluding Sts 19 from Australopithecus africanus
Author(s) -
Ahern James C. M.
Publication year - 1998
Publication title -
american journal of physical anthropology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.146
H-Index - 119
eISSN - 1096-8644
pISSN - 0002-9483
DOI - 10.1002/(sici)1096-8644(199804)105:4<461::aid-ajpa5>3.0.co;2-r
Subject(s) - biology , synapomorphy , zoology , primate , homo sapiens , phylogenetics , ecology , anthropology , genetics , clade , sociology , gene
Two analyses conclude that Sts 19 cannot be accommodated within the Australopithecus africanus hypodigm (Kimbel and Rak [1993] In Kimbel and Martin [eds.]: Species, Species Concepts, and Primate Evolution. New York: Plenum, pp. 461–484; Sarmiento [1993] Am. J. Phys. Anthropol. [Suppl.] 16: 173). Both studies exclude Sts 19 because it possesses synapomorphies with Homo. Furthermore, according to Kimbel and Rak (1993), including Sts 19 in A. africanus results in an unacceptably high degree of polymorphism. This study aims to refute the null hypothesis that Sts 19 belongs to A. africanus. Twelve basicranial characters, as defined and implemented in Kimbel and Rak's study, were scored for casts of seven A. africanus and seven Homo habilis basicranial specimens. These characters were also examined on specimens from a large (N = 87) sample of African pongids. Contrary to Kimbel and Rak's (1993) findings, the null hypothesis is not refuted. The degree of polymorphism among A. africanus with Sts 19 included is less than that seen in Pan troglodytes. In addition, Sts 19 shares only one apomorphy with Homo. However, when treated metrically, Sts 19's morphology for this character is not significantly divergent from other A. africanus specimens. Am J Phys Anthropol 105:461–480, 1998. © 1998 Wiley‐Liss, Inc.