The faces of predecessors to the human "Homo" genus evolved to protect against human fists, according to a new study in the scientific journal Biological Reviews. The study contends that early violence played a larger role in our evolution than did eating habits, as previously suggested.
According to lead author David Carrier, the "feeding hypothesis," which suggests that our ancient ancestors had strong jaws to crack nuts and other hard foods, doesn't make all that much sense because the australopith man most likely ate fruit. Rather, Carrier and co-author Michael Morgan, offer the "protective buttressing hypothesis." Says Carrier:
Jaws are one of the most frequent bones to break -- and it's not the end of the world now, because we have surgeons, we have modern medicine... But four million years ago, if you broke your jaw, it was probably a fatal injury. You wouldn't be able to chew food... You'd just starve to death.
The authors write in the paper's abstract that "when humans fight hand-to-hand the face is usually the primary target and the bones that suffer the highest rates of fracture are the parts of the skull that exhibit the greatest increase in robusticity during the evolution of basal hominins... In this review, we suggest that many of the facial features that characterize early hominins evolved to protect the face from injury during fighting with fists."
The theory also explains why such marked differences existed between early male and female faces. According to Carrier, "it's males that are most likely to get into fights," over resources, and women. The authors write that the bones in question are "the most sexually dimorphic parts of the skull in both australopiths and humans."