Final answer:
The indentation of the cranium behind the eyes refers to aspects of the human skull's anatomy such as the brow ridges and frontal bone, which form the structure of the orbit and cranial cavity.
Step-by-step explanation:
An indentation of the sides of the cranium behind the eyes is related to the anatomy of the human skull. The frontal bone forms the supraorbital margin of the orbit and it is thickened just above this margin, forming rounded brow ridges. These ridges, which are larger in males, are situated directly behind the eyebrows. The frontal bone further extends posteriorly within the cranial cavity, creating both the roof of the orbit below and the floor of the anterior cranial cavity above. Additionally, the greater wings of the sphenoid bone are lateral projections of the sphenoid bone that establish the anterior wall of the middle cranial fossa and contribute to the lateral structure of the skull.
Other significant features mentioned include the external occipital protuberance, which is a small bump found on the posterior skull, and the lacrimal fossa, a shallow depression formed by the lacrimal bone in the front-inner wall of the orbit. The anatomy has evolved to accommodate the expansion of the brain, particularly the cerebrum, correlating with an increase in higher intellectual functions and resulting in changes to the shape of the cranium and face.