Sofia Pereira Pedro and Emiliano Bruner, of the Paleoneurobiology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), have just published a morphometric study of the spatial relationship between eyes and brain in modern and fossil humans and chimpanzees, in the Journal of Anatomy.

In the case of Homo sapiens, the frontal and temporal lobes are separated from the face only by a very fine layer of bone, and the evolution of a very large brain and a very small face have given rise to a competition for space between the development of the eyes and the cerebral cortex.

“Our eyes and sockets are below the frontal lobes of the brain, while chimpanzees have them further forward, anterior to the frontal lobes. In fossil hominids, we observe an intermediate situation”, states Emiliano Bruner.

According to this study, in which both the soft tissues (eyes and brains) and the “hard tissues”, that is the anatomy of the cranium (eye sockets and cranial cavity), were analyzed, using magnetic resonance and computerized tomography, respectively, the architecture of the cranium in modern humans may have imposed constraints upon the developmental possibilities, above all in the case of the eye, whose deformation due to lack of space may affect the capacity for vision.

The main factors determining the differences between individual adults are the distance between the eyes and temporal lobes of the brain and the orientation of the sockets. Depending on these variations, individuals may have greater or lesser susceptibility to deformation of the eyeball caused by spatial limitations.

This study, entitled “Shape analysis of spatial relationships between orbito-ocular and endocranial structures in modern humans and fossil hominids”, was the result of collaboration with Michael Masters of Montana Tech. (USA), with whom Emiliano Bruner had already published another study of the correlation between the size of the eye and the size of the different cerebral lobes, in 2015.