MIXTURE ANALYSIS AND ITS PRELIMINARY APPLICATION IN ARCHAEOLOGY

Sexual dimorphism has been a special concern in human origins studies. Not only must sexual dimorphism be considered in attempts to determin e sex ratios in archaeological faunal materials and prehistoric human population samples, but assessing the nature and degree of sexual dimo rphism in various hominid species in the past can be crucial for under standing the nature and rate of hominid evolutionary change and someti mes to a certain degree for making species designations among (hominid or other) specimens. Obtaining sex ratio in a population is easy if e ach individual in the population can be accurately sexed through the u se of one or more objective variables. But this is often impossible, d ue to the incompleteness of the osteological record. One does not, how ever, have to sex each individual in a population in order to ''sex th e population''. Mixture analysis is a statistical method that can be u sed to deal with the problem of sexing the population without knowing the sex of any individual member. This paper introduces some basic con cepts and procedures of mixture analysis, gives a brief review of its development and previous applications in various fields, discusses som e preliminary results of its application to the tooth metric data of A frican early hominids, of the Lufeng hominoids and of the two cervid s pecies (Megaloceros pachyosteus and Pseudaxis grayi) from the Homo ere ctus site at Zhoukoudian Locality 1. The quantitative results of this research are compared to previous qualitative assessments of the same materials. A control study to test the power of mixture analysis to di scriminate sexual dimorphism was conducted on metric dental data from modern great apes, the results compared to the known metric patterns. Analysis of hominid/hominoid tooth data indicates that there are more males than females in A. robustus and more females than males in A. af arensis; there appears to be more than one species of hominoid represe nted at the site of Lufeng in China; and there are more females than m ales in the alleged smaller species among the Lufeng hominoids. The an alysis of cervids from Zhoukoudian Locality 1 suggests that there are more females than males for the Megaloceros pachyosteus and more males than females for the Pseudaxis grayi; Pseudaxis grayi is dentally mor e sexual dimorphic than Megaloceros pachyosteus. The analysis shows th at mixture analysis has great potential for determining sex ratios and the degree of sexual dimorphism for zooarchaeological and palaeontolo gical researches. (C) 1997 Academic Press Limited.