Canine size variability in extinct hominin taxa with special emphasis in the homo habilis: Palaeobiological and taxonomical implications

Abstract

The canines of hominins are quite different in both size and shape compared to those of their closest extant relatives (chimpanzees and gorillas). On the other hand, it has been argued that canine size and sexual size dimorphism is related to socio-sexual behaviour, but there is only limited evidence as to whether these aspects are informative regarding the behaviour of extinct hominins. This issue is complicated by the difficulty to sex the upper canines of fossil hominins and uncertain taxonomic attribution. In order to make palaeobiological inferences on the behaviour of these taxa, in this paper the variability in upper canine area is evaluated in extinct hominins, on the basis of the coefficient of variation, by using re-sampling procedures. Particular emphasis is put on Homo habilis s.l., by evaluating variability in several groupings of upper canines attributable to this taxon. The results indicate that, in most instances, extinct hominins cannot be significantly distinguished from chimpanzees and modern humans regarding canine area variability. It is therefore concluded that canine area is not a good variable to infer behavioural aspects of extinct hominins. In addition, when the sets of H. habilis s.l. including KNM-ER 1590 (a 1.85 My older H. rudolfensis representative described as a juvenile male) showed a variability superior to that of anatomically modern humans, which suggests those sets including such individual may represent more than one taxon