Center for the Study of Human Origins, Department of Anthropology, New York University, New York Consortium in Evolutionary Primatology
March 27, 2015 , Archview Ballroom
Hominins are characterized by a shift towards bipedalism, increased brain size, and a diversity of dietary specializations that may include both morphological (e.g. the enlarged masticatory apparatus of Paranthropus) and behavioral (e.g. tool use) adaptations. While ecological change has long been linked to change in both cranial and postcranial morphology, the interactions between these anatomical regions remain difficult to interpret. To determine whether postcranial morphology may have constrained the evolution of cranial form, I tested the hypothesis that important cranial morphologies are linked to postcranial morphology, approximated using the atlas and axis vertebrae. Linear and 3D measurements from a sample of recent humans and chimpanzees (n=103) were analyzed using two-block partial least squares, providing RV coefficients (a general measure of correlation). Preliminary results indicate that the basicranium is correlated with postcranial morphology (humans only RV=0.2394, p=0.004) but the strength of this relationship may be greater in chimpanzees (combined RV=0.6175, p<0.0001), despite similar overall levels of morphological variation in the two taxa. Additionally, consistent with previous work, lateral structures of the human basicranium appear more weakly correlated with postcranial morphology than midline structures (RV=0.0834-0.1321, p>0.05 versus RV=0.1264-0.1662, p<0.05, respectively), suggesting the lateral basicranium is less constrained in humans than in other apes. These results may suggest that hominin crania were able to evolve fairly independently of the postcranium, resulting in a greater range of morphological diversity than in other apes. A possible source of this independence may be the adoption of bipedalism, which also resulted in reduced integration in the thorax.
Funding for this project was provided by the Margaret and Herman Sokol Travel/Research Award from New York University.