How Thick Is the Average Human Skull?
The thickness of the average human skull, or that part of the skull called the cranium that encloses the brain, is a quarter of an inch. The skull is made up of two thin layers of bone sandwiching a thin layer of bone marrow. It is most thin around the temples, where the thickness may be only an eighth of an inch.
The thickness depends on a number of factors, including gender. The average skull thickness for men is .25 inches, and the average for women is .28 inches. Although women’s skulls are thicker than men’s on average, their skulls are smaller, with the average front-to-back measurement being 6.73 inches for women and 6.93 inches for men.
Though skull thickness is thought to improve the outcome for anyone experiencing a head injury, skull shape is also believed to play a role in how well a person responds to trauma to the head. Another thing of note is that skulls thin with age. In the case of Paget’s disease, which is indicated by the thickening of bones, the skull has been known to be as much as one inch thick in parts.
Functions of the skull include protection of the brain, fixing the distance between the eyes to allow stereoscopic vision, and fixing the position of the ears to enable sound localisation of the direction and distance of sounds. In some animals such as horned ungulates, the skull also has a defensive function by providing the mount (on the frontal bone) for the horns.
The skull protects the brain from damage through its hard unyieldingness; the skull is one of the most durable substances found in nature with it needing the force of about 1 ton to reduce the diameter of the skull by 1 cm. In some cases, however, of head injury, there can be raised intracranial pressure through mechanisms such as a subdural haematoma.
In these cases the raised intracranial pressure can cause herniation of the brain out of the foramen magnum (“coning”) because there is no space for the brain to expand; this can result in significant brain damage or death unless an urgent operation is performed to relieve the pressure. This is why patients with concussion must be watched extremely carefully.
Dating back to Neolithic times, a skull operation called trepanation was sometimes performed. This involved drilling holes in the cranium. Examination of skulls from this period reveals that the “patients” sometimes survived for many years afterward. It seems likely that trepanation was performed for ritualistic or religious reasons and not only as an attempted life-saving technique.