Abstract

We report here on the results of a new cladistic analysis of early hominid relationships. Ingroup taxa includedAustralopithecus afarensisAustralopithecus africanusAustralopithecus aethiopicusAustralopithecus robustusAustralopithecus boiseiHomo habilisHomo rudolfensisHomo ergasterandHomo sapiensOutgroup taxa includedPan troglodytesandGorilla gorillaSixty craniodental characters were selected for analysis. These were drawn from the trait lists of other studies and our own observations. Eight parsimony analyses were performed that differed with respect to the number of characters examined and the manner in which the characters were treated. Seven employed ordered characters, and included analyses in which (1) taxa that were variable with respect to a character were coded as having an intermediate state, (2) characters with variable states in any taxon were excluded; (3) a variable taxon was coded as having the state exhibited by the majority of its hypodigm, (4) variable taxa were coded as missing data for that character, (5) some characters were considered irreversible, (6) masticatory characters were excluded, and (7) characters whose states were unknown in some taxa were excluded. In the final analysis, (8) all characters were unordered. All analyses were performed using PAUP 3.0s. Despite the fact that the eight analyses differed with respect to methodology, they produced several consistent results. All agreed that the "robust" australo-pithecines form a clade,A. afarensisis the sister taxon of all other hominids, and the genusAustralopithecusas conventionally defined, is paraphyletic. All eight also supported trees in whichA. africanusis the sister taxon of a jointHomo+ "robust" clade, although in one analysis an equally parsimonious topology foundA. africanusto be the sister of the "robust" species. In most analyses, the relationships ofA. africanusandH. habiliswere unstable, in the sense that their positions vary in trees that are marginally less parsimonious than the favored one. Trees in which "robust" australopithecines are paraphyletic were found to be extremely unparsimonious.