COMPARISON OF 4 SIMPLE METHODS FOR ESTIMATING SEXUAL DIMORPHISM IN FOSSILS

Estimating sexual dimorphism in skeletal and dental features of fossil species is difficult when the sex of individuals cannot be reliably d etermined. Several different methods of estimating dimorphism in this situation have been suggested: extrapolation from coefficients of vari ation, division of a sample about the mean or median into two subsampl es which are then treated as males and females, and finite mixture ana lysis (specifically for estimating the maximum dimorphism that could b e present in a unimodal distribution). The accuracy of none of these m ethods has been thoroughly investigated and compared in a controlled m anner. Such analysis is necessary because the accuracy of all methods is potentially affected by fluctuations in either sample size, sex rat io, or the magnitude of intrasexual variability. Computer modeling exp eriments show that the mean method is the least sensitive to fluctuati ons in these parameters and generally provides the best estimates of d imorphism. However, no method can accurately estimate low to moderate levels of dimorphism, particularly if intrasexual variability is high and sex ratios are skewed. (C) 1994 Wiley-Liss, Inc.