Underestimating intraspecific variation: The problem with excluding Sts 19 from Australopithecus africanus
Article first published online: 6 DEC 1998
Copyright © 1998 Wiley-Liss, Inc.
American Journal of Physical Anthropology
Volume 105, Issue 4, pages 461–480, April 1998
How to Cite
Ahern, J. C. M. (1998), Underestimating intraspecific variation: The problem with excluding Sts 19 from Australopithecus africanus. Am. J. Phys. Anthropol., 105: 461–480. doi: 10.1002/(SICI)1096-8644(199804)105:4<461::AID-AJPA5>3.0.CO;2-R
- Issue published online: 6 DEC 1998
- Article first published online: 6 DEC 1998
- Manuscript Accepted: 31 DEC 1997
- Manuscript Received: 27 JAN 1997
- H. Rackham School of Graduate Studies, University of Michigan
- Homo habilis
Two analyses conclude that Sts 19 cannot be accommodated within the Australopithecus africanus hypodigm (Kimbel and Rak  In Kimbel and Martin [eds.]: Species, Species Concepts, and Primate Evolution. New York: Plenum, pp. 461–484; Sarmiento  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.