1Faculty of Medicine in the Galilee, Bar Ilan University, 2Department of Anatomy, Sackler Faculty of Medicine, Tel Aviv University, 3Department of Physical Therapy, Zefat Academic College
Thursday All day, Clinch Concourse
The evolutionary changes of the hominid cranial base have been studied and debated extensively. Most authors tend to contrast pongids with humans, usually examining the midline, especially the basicranial angle. Studies of shape changes of the endocranium tend to focus on cortical expansion in humans, perhaps overshadowing other evolutionary process that happened in the lower endocranium.
In order to asses changes within the lower endocranium, we used 3D geometric morphometric to capture the shape of the whole endocranium in humans and chimpanzees (n=30). 229 landmarks and semilandmarks were acquired for the whole endocranium, and 122 landmarks and semilandmarks were acquired separately for the lower endocranium. A color-coded vector map was produced to visualize shape differences between groups. Data was analyzed in three parts: we compared the whole endocranium without omitting size; the same was done while omitting size, thus observing just shape. Finally, we compared the shape of the lower part of the endocranium.
We found that while including size, the upper part of the endocranium, contributes mostly to shape changes. Omitting size brings out the changes in the frontal and parietal area, and some changes within the cranial base, such as anterior movement of the foramen magnum. Looking just at the lower endocranium, the evolutionary changes become clear: anterior movement and angular changes of the posterior cranial fossa; expansion of the temporal lobes; and expansion of the cerebellar areas.
Adding australopithecines into the analysis emphasizes the fact that major morphological changes took place long before brain expansion.