The left and right hemispheres of the human brain are specialized for different cognitive tasks. This functional lateralization is reflected in the morphological asymmetry of the brain. Based on brain imprints in bone (endocasts), however, we recently found that our closest living relatives, the great apes, share the same mean asymmetry. This challenges the longheld view that the pattern of brain asymmetry is unique to humans (Neubauer et al., 2020), and suggests that an ancestral pattern of asymmetry was adopted for typical human lateralized abilities and to reinforce the functional and developmental modularization of the human brain. However, little is known about the developmental dynamics of brain asymmetry and whether developmental trajectories differ between humans and apes.
Here, I will investigate ontogenetic changes of brain asymmetry in humans, chimpanzees, gorillas, and orangutans to assess how and when the typical asymmetry pattern arises in development and when variation in humans deviates from that in great apes. Based on endocasts as proxies for the brain, I will model the developmental dynamics of directional and fluctuating asymmetry and try to disentangle functional lateralization, developmental instabilities and allometric effects. I will rely on state-of the art geometric morphometrics based on 3D (semi)landmarks captured from CT scans. I combine an evo-devo approach with novel multivariate methodology to overcome the classic typological approach of studying brain asymmetry, which tends to overlook important aspects of asymmetry and neglects individual variation. This comparative approach promises novel insights into the development and evolution of human brain asymmetry interesting for discussions in paleoanthropology, evolutionary neuroscience, cognitive biology, primatology, and archaeology.