Did that feature evolve to take a punch?
Were the jaws beefed up as well?
Did that feature evolve to take a punch?
Were the jaws beefed up as well?
well, according to these people, it doesn’t have anything to do with chewing. Why would you assume it has anything to do with being punched?
Arch Oral Biol. 1991;36(4):273-81.
Function of the supraorbital region of primates.
Hylander WL1, Picq PG, Johnson KR.
The purpose of this study was to test the hypothesis that the functional significance of well-developed brow-ridges in primates is to counter powerful masticatory forces during chewing and biting. This was done by measuring and analysing patterns of in vivo bone strain recorded from rosette strain gauges bonded to the supraorbital region of Macaca fascicularis (the crab-eating or long-tailed monkey) and Papio anubis (the olive baboon) during mastication and incision. It was found that the supraorbital region is strained relatively little during mastication and incision. This indicates that in macaques and baboons there is much more supraorbital bone than is needed to counter masticatory loads, which in turn suggests that their brow-ridges could be considerably smaller yet still counter masticatory stress without structural failure. Therefore, there is no good reason to believe that enlarged brow-ridges in living and/or fossil primates are structural adaptations to counter powerful masticatory forces.
PMID: 2064549 [PubMed - indexed for MEDLINE]
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What other evolutionary advantage could there be to having a bony ridge across the middle of your face?
That’s one hypothesis:
I presumed it to be just one feature of a more robust skull and skeleton in general. Lots of active hunting and climbing in our ancient ancestors to get injuries from.
The mysterious skulls of Java man and Peking man may have evolved because males were clubbing each other in fights.](http://www.naturalhistorymag.com/htmlsite/master.html?http://www.naturalhistorymag.com/htmlsite/0204/0204_feature.html)
All primates have a pronounced brow ridge. See here to compare the skulls of gorillas, chimpanzees, early hominids and modern humans. The most cited reason for its prominence is that it developed to reinforce the skull for the stresses that chewing food puts upon it.
The reason that the brow ridge is not so visible on anatomically modern humans is more to do with the increase in brain size at the frontal lobe over the eyes.
That’s incorrect. The brow ridge in modern humans is much less robust than in Homo erectus and other earlier humans.
Well could part of it also be a sexual signal of high testosterone as well as a threat display? I was reading some articles about angry faces and the parts of the face they exaggerate, if you make an angry face you can see and feel how it makes the brow seem even larger which in theory should make you appear more threatening. A smoother, less prominent brow ridge is also considered a neotenous trait according to wiki.
Looking at the array of primate skulls that’s no doubt true, but as the primate brain developed and grew in size, generally upwards and towards the front of the head, that would also have the effect of reducing the visual prominence of the brow ridge. Comparison of chimpanzee and human brains/skulls.
It may have reduced the visual prominence, but the fact is that the supraorbital ridge is also less robust in modern humans than it is in earlier ancestral humans.
Yes. But note that the OP asks about the brow ridge in “human ancestors”, which I take to refer to species that precede home sapiens. And the various articles linked also refer to ancestor species, not to our own species. So it could be that the prececessor species retained or developed the heavy brow for the reason suggested, but that we have tended to lose it because either (a) we are intelligent enough to find better ways to avoid being injured in a fight, or (b) we are intelligent enough to use tools in a way which makes our fighting much more effective, and a heavy brow ridge no longer provides a useful degree of immunity.
I’m going for (b) myself; the articles cited link the heavy brow ridge with the development of the hand to the point where it makes a useful fist. But when you stop hitting people with your fists, and start hitting them with clubs and axes, that’s a game-changer.
It’s also hypothesized that the modern human body form developed due to strong selection for long-distance endurance running, in order to be able to pursue prey to their exhaustion or beat other scavengers to dead animal carcasses.
There are a number of changes in the human anatomical form that support this hypothesis. A lighter skull, with consequentially reduced brow ridge size, would likely help to reduce overheating of the brain during running. Also, the more balanced human head, with a flatter face than previous human ancestors, has been suggested to aid in running by shifting the center of mass back, making it easier to balance when moving at speed.
It seems obvious to me that heavy brow ridges and massive jaws were already present in human ancestors, not evolved afterwards in response to the way we conducted social violence after we started acting more like humans than jungle-dwelling apes.
Gorillas and chimps (who don’t punch or club each other like we do) have much more robust skull features than us, and the trend as human ancestral species evolved seems to be for those heavy features to gradually become reduced. If there were pressure to increase their size in response to blunt force trauma, you wouldn’t see the trend you do.
So just because a physical feature might be useful in a certain circumstance, doesn’t mean it evolved for that reason; it could be complete coincidence.
It’s also worth pointing out that the prominent chin of the modern human is considered as one of its defining anatomical features, compared with other primates.
While the reason for its emergence is still a matter of debate (and other theories include adaptation for speech or sexual selection), analyses have supported the idea that it is well-developed to deal with mechanical stress, including chewing.
Since chewing has been suggested as the reason for the prominent brow ridge of primates, it would make sense that the chin of the modern human developed in projection to compensate for the reduction in size of the brow ridge. It could be conjectured that the driving force for the need to reduce bone mass in the upper part of the cranium was for the dissipation of heat to keep the brain cool.
On the other hand, as any boxer will tell you, a strong chin is desirable if one is going to be punched in the face!
Makes for good musicians.
To add even more, it’s worth pointing out that the thickness or bone mass distribution of your skull or jaw has very little to do with how good a “chin” you have. The types of KOs or TKOs you see in combat sports or street fights (and even a lot of non-combat accidents) seldom happen because someone’s skull got fractured. They happen because the head got accelerated very fast in a direction which caused the brain inside to bounce off the inside of the skull… most of these KOs involve just soft tissue damage.
You see all the time in combat sports athletes who’s skulls look entirely normal or even somewhat small who are incredibly difficult to knock out. There are also Frankenstein-looking monster-skulled athletes who routinely get put down. A couple things that have a much bigger impact on how good a chin you have are how strong your neck is and most importantly how fast your reflexes are… when you see a punch coming you can tense up or start to roll with it, even it you can’t avoid getting hit by it. It doesn’t take much movement to deflect enough force to avoid a KO, but if you don’t see a blow coming there’s a good chance it’ll take you down (if well delivered).