Assessing exact randomization-based methods for determining the taxonomic significance of variability in the human fossil record

The identification of fossil hominin species is one of the principal challe nges in human palaeontology. Here, we use metrical data from extant primate species and Plio-Pleistocene hominin specimens to evaluate four exact rand omization-based methods for assessing specific diversity in the fossil reco rd. The first method is based on size dimorphism, the second on average tax onomic distance, the third on size-corrected average taxonomic distance, an d the fourth on the standard error of the slope in least squares regression . The study examines how the methods compare with respect to the sire and/o r shape information they recover, and how their conclusions regarding the s pecific affinities of hominin specimens are affected by different comparati ve samples. The study also Investigates how the methods are affected by any overlap between intra- and interspecific variability within the reference samples, and how they compare with respect to the fossil specimens they sug gest should be considered to be conspecific. The outcome of these analyses suggests that the results of recent exact randomization analyses of Plio-Pl eistocene hominin specific diversity should be interpreted with caution.