Morphological and molecular measures of papionine diversity as standards for the interpretation of hominin diversity.

Abstract

We report early results from a comprehensive project that uses landmark morphometrics and superquadric modeling based on 3-D surface point coordinate mapping and visualization (Sommer et al. 2006, this meeting) to gauge morphological differences among papionine primates known to exchange genes among conventional species level taxa. Morphological findings are compared with genetic measures on the same populations. Papionine biological diversity has received extensive study recently. Unlike recurrent taxonomic rearrangements of disjunct Linnaean categories, our investigations focus on comparisons of phenostructure and zygostructure (Jolly 1993) in order to test hypotheses concerning broader patterns of early hominin evolutionary continuity (Henneberg and Thackeray 1995, Henneberg 1997, Henneberg and de Miguel 2004, Eckhardt 2000). Our primary data set comprises ≤66 measurement points on 1348 cranial specimens distributed among 42 nominal species and genera of papionine primates (with taxon sample sizes ranging from 1 to 88); data collection is continuing and being extended to elements of the postcranial skeleton. Given the large and expanding size of our data set, only selected findings are reported here. For example, a maximum parsimony tree of mitochondrial COII (Disotell 1992) groups Cercocebus with Mandrillus, while Lophocebus is placed closer to the pairing of Theropithecus with Papio. However, a matrix of distances between cranial vault points normalized by geometric means shows that Cercocebus differs by ≥5% from Mandrillus in three times as many comparisons as Cercocebus differs from Lophocebus, and six times as many comparisons as Lophocebus in turn differs from Mandrillus. Clearly, morphometric differences can misrepresent genetic distances drastically. Support for this investigation was provided by the Australian Research Council, the Pennsylvania State University College of Health and Human Development, and the Department of Kinesiology’s Davis Fund for the Encouragement of Innovative Research.