Thick Skull a Survival Trait 58
Waffle Iron writes "This article at cnn.com reports: 'Scientists say the bulky craniums of the human ancestor, homo erectus, may have helped the species survive some aggressive mating rituals. After studying fossils in a region called Dragon Bone Hill in China, anthropologist Russell Ciochon of the University of Iowa concluded males of the species were clubbing one another over the head, probably to win females.' However, the geekier cavemen may have won out at the end. The article goes on to say: '...evolution eventually favored a lighter skull to accommodate a heavier and larger brain'."
Skull features (Score:5, Informative)
The article fails to go into depth concerning any of Homo erectus' actual skull features which might have lessened trauma in a conflict.
H. erectus skullcaps are pachyostic, meaning to possess an increase in size, density, or mineral content. There is a thickening along the midline of the skull that resembles a boat's keel. Thusly, it is referred to as "sagittal keeling". Also, there is a projecting brow ridge with which most people are familiar and bony thickenings on the sides and rear of the cranium.
If a heavy blow were to hit a modern human on the top of his or her head, the bone would cave in. Hematoma, coma, and death are likely results of this. The thicker bone of erectoids is less likely to fracture on impact.
Anyone who's been in a fight though, will tell you that you're probably going to deliver blows at eye-level. The thick ring of bone starting above the eye sockets and continuing around the skull help protect against trauma to the head. For one, your eye sockets are protected because of the brow ridge. Secondly, you have thick bones above your temples and ears to protect the sinuses that conduct blood into the internal jugular vein. The ridge on the rear of the skull protects sinuses carrying blood to the cerebullum and occipital lobe of the brain.
The roofs of H. erectus eye sockets are flat and horizontal and any blow to them would be transmitted to the back of the skull, thusly protecting the bones around the eye. The H. erectus face was also tucked under brow ridges, which made it harder to fracture cheek bones and to separate the facial skeleton from the braincase.
The jaw also thickens just behind the chin, the most common place for breaks in modern peoples. Erectoids differed from modern humans in the placement of arteries in and around the temple area. The main blood supply of the meningeal artery was moved away from this vulnerable area because the bone there was particularly thin and this movement lessened the effects of the breakage of arteries in that area.
There are other differences, but those are the major ones covered in the work of Ciochon and Boaz.