Zero to Two Million Years Ago: Sexual Dimorphisms in Very Early Humans
Human Sexual Dimorphism -- the Current View Two Fossils -- Neanderthalers and Homo erectus Present Evidence of Sexual Dimorphism? New Studies -- Individual Dimensions of Teeth -- Univariate Sexual Dimorphisms Homo habilis -- an Anticipation of Chapter Five Dimensions of Teeth in Combination -- Multivariate Sexual Dimorphisms Homo habilis again -- a Second Anticipation of Chapter Five Summary -- Sexual Dimorphisms in Fossil Homo
Abstract: We first review briefly the current evidence of sexual dimorphism in Homo sapiens neandertalensis and Homo erectus. In the remainder of the first half of this chapter we then examine, one by one, individual lengths and breadths for such samples of teeth of these two species as are available. In comparison with the situation in the extant apes and humans of the last chapter, we do not know here which specimens of which fossil belong to which sex. Accordingly, therefore, the data are examined as a whole. The distributions that are obtained are used to reveal to us what, if any, evidence there may be of sexual dimorphism. Again, in contrast to the living forms, instead of assuming that we know the ratios of the number of each sex in the fossil species, we examine the distributions obtained to see if they suggest any specific sex ratios to us.
Although most investigators believe that the fossil, Homo habilis, despite its designation, is generally closer to australopithecines than to Homo we have here anticipated the chapter on the australopithecines by describing briefly the results for that group.
In the second half of this chapter we study the fossils multivariately by intercalating them within the morphometric studies of Chapter 2 on the living forms. However, this cannot be done in the same way as for the living forms; we just do not know which specimens are from which sex. Accordingly, therefore, we estimate the modes for each sex for each dimension using information from the univariate studies, that suggests when marked sexual differences may be present. This process allows us to see clearly the relationships of the fossils to the living forms, especially, of course, to modern Homo to which, naturally, they are most close. It also allows us to see, if somewhat more mistily, the nature of such multivariate sexual dimorphisms as may exist.
We again anticipate some of the results of Chapter 5 by reviewing briefly the place of Homo habilis within these studies.
Both the univariate and multivariate steps in this analysis show an obvious relationship between the two groups of fossil Homo and the modern species. They also show how completely different they are from the various apes. The place of Homo habilis in these studies is especially interesting.
Most of the enquiries into sexual dimorphism in fossil groups of humans have depended upon the notion that to study this, it is essential to know the sex of each individual specimen. Yet the materials that are most abundant are teeth and these do not bear recognizable gonads. Accordingly most of the definitive investigations have been confined to study of samples of teeth that are associated with other skeletal materials for which adequate sexual determinations can be made: i.e. where the remains include especially, for instance, the pelvis.
Thus Brace and Ryan ( 1980) have presented extensive studies of sexual dimorphism in human teeth back as far as the last 40,000 years. However, it becomes increasingly difficult to assign fragments to identifiable individuals. Thus, the number of remains for which accurate sexual determinations