ORIGINAL ARTICLE doi:10.1111/j.1558-5646.2011.01508.x MORPHOLOGICAL INTEGRATION IN THE HOMININ DENTITION: EVOLUTIONARY, DEVELOPMENTAL, AND FUNCTIONAL FACTORS Aida Gomez-Robles´ 1,2 and P. David Polly3 1Konrad Lorenz Institute for Evolution and Cognition Research, Adolf Lorenz Gasse 2, A-3422 Altenberg, Austria 2E-mails:
[email protected];
[email protected] 3Department of Geological Sciences, Indiana University, 1001 East 10th Street, Bloomington, Indiana 47405 Received June 29, 2011 Accepted October 19, 2011 As the most common and best preserved remains in the fossil record, teeth are central to our understanding of evolution. However, many evolutionary analyses based on dental traits overlook the constraints that limit dental evolution. These constraints are di- verse, ranging from developmental interactions between the individual elements of a homologous series (the whole dentition) to functional constraints related to occlusion. This study evaluates morphological integration in the hominin dentition and its effect on dental evolution in an extensive sample of Plio- and Pleistocene hominin teeth using geometric morphometrics and phyloge- netic comparative methods. Results reveal that premolars and molars display significant levels of covariation; that integration is stronger in the mandibular dentition than in the maxillary dentition; and that antagonist teeth, especially first molars, are strongly integrated. Results also show an association of morphological integration and evolution. Stasis is observed in elements with strong functional and/or developmental interactions, namely in first molars. Alternatively, directional evolution (and weaker integration) occurs in the elements with marginal roles in occlusion and mastication, probably in response to other direct or indirect selective pressures.