The human face evolved to take a punch? Spoiler: no

The human face evolved to take a punch! That’s the interesting (and slightly out-there) claim researchers made yesterday. And like many interesting (and slightly-out there) ideas it was gobbled up by the press; with articles about it appearing at the Guardian, BBC, and many more. But is there any merit to this claim?

Difficult to say based on news reports as they contain scant information about how these scientists actually arrived at this conclusion (do they ever?). Fortunately, with a little help from the internet, I was able to dig up the research paper which started all this (and is available for free, if you want to read along at home). And after reading it I feel confident in saying: nope. They provide no compelling reason to think that the human face evolved to withstand a punch.

The research revolves around grade 2 & 3 hominins; which lived from around 4 million years ago until ~2 million years ago. These were the members of our family that first began to spend a lot of time walking upright on the ground. However, as well as the evolutionary changes one might expect to see in animals becoming more reliant on bipedalism, their skulls underwent some significant changes too.

They become much more robust; with large, thick bones. Their jaws in particular became especially powerful, in some species reaching crazy extremes that gave them a more powerful bite (relatively speaking) than any living ape1. These jaws could also explain the robusticity in other parts of the skull, as it would have provided an anchor for powerful chewing muscles and/or reinforcement against these huge force2. Based on all this most people concluded that these weirdly powerful skulls were adaptations to a diet that would require a lot of chewing (a conclusion supported by the fact their diet does appear to have involved a lot of chewing3).

On the left is Australopithecus,

The really robust skulls seen in these hominins. From left to right: Australopithecus africanus, Paranthropus robustus, Paranthropus boisei, Paranthropus aethiopicus. Note: none of these are thought to be direct ancestors of humans

However, the face-punch-paper begs to differ; arguing that there are some things this whole “diet” idea can’t explain.

  1. Why do these skulls differ between the sexes? After all, both surely had the same diet
  2. Many parts of the skull that became robust experience relatively limited forces during chewing.
  3. Aside from Paranthropus robustus and Paranthropus boisei, there’s no evidence the other species ate hard/tough food.

Instead they point out that during unarmed fights it is the face that typically gets hit the most. In fact, in many American hospitals fisticuffs is the leading cause of injury to the face; causing a greater portion than even car accidents. So they posit that these robust skulls are actually an adaptation to this sort of injury, helping to reduce it. And from there they really run with the idea.

Where people get injured in fights

Where people get injured in fights

The powerful chewing muscles, for example, aren’t to chew; they act as padding to protect the skull. The large teeth aren’t to transfer the force of chewing to food, but to transfer the force of being punched in the jaw to the rest of the skull; spreading it over a wider area and reducing the damage. The differences between the sexes are because it was men who were getting into fights. The bits of the skull that became robust that weren’t linked to chewing are often damaged in fights, hence why they got bigger and stronger.

But all of these amount to a “just so” story. As the space-ape saga shows; it’s easy to cherry pick evidence to fit almost any conclusion. Ultimately you need to try and test the underlying assumption on which your idea is based. In this case there are two fundamental ideas: (a) fighting was a significant evolutionary force in these hominins and (b) that fighting was similar enough to how modern Americans fight that it routinely resulted in similar injuries. Unfortunately, at no point do they attempt to test these premises.

They point to no injuries in fossils that might indicate these hominins were fighting. They provide no evidence that the pattern of injuries seen in fighting in America is the pattern we would expect to see throughout human history. A cross-cultural study, for example, showing that face punching is prevalent in hunter-gatherers would go a long way to showing this. Further, about how other primates fight suggest that these would be important factors either. Chimps, for example, are one of the most aggressive apes yet their fights rarely result in injuries (and when they do they’re typically to the hands4).

Not that all this means our ancestors weren’t fighting, just that without any additional evidence confirming these basic assumptions, there’s very little to suggest they were; and the entire idea that the human face evolved to survive fights comes crashing down. It boils down just an assertion; and not much else.

But about their criticism of the diet hypothesis? Well I don’t think they hold much water either. This could be the topic of an entire other post, but briefly speaking:

  1. The sexual dimorphism of these species falls within the range of variation seen in living apes, who don’t punch each other in the face (and have the same diet to boot5)
  2. Individual bones of the skull don’t appear to evolve independently. Instead they evolve as a unit, so bones which might not play a huge role in eating would still change if other bones were.
  3. For P. aethopicus, it’s not like we’ve looked at their diet and found that they didn’t eat hard/tough stuff. There’s just very little information on their diet to begin with. For the other species for which there is no evidence of eating hard/tough food, Au. africanus, it appears that the premolars would play the biggest role in chewing it. Yet research has focused on the molars6.

In other words, the preponderance of evidence indicates that these members of our family had weird faces to deal with a weird diet. The idea that it was actually an adaptation to fighting is based on assumptions for which no evidence is provided.


  1. Demes, B., & Creel, N. (1988). Bite force, diet, and cranial morphology of fossil hominids. Journal of Human Evolution17(7), 657-670.
  2. Wood, B., & Constantino, P. (2007). Paranthropus boisei: fifty years of evidence and analysis. American journal of physical anthropology134(S45), 106-132.
  3. Constantino, P. J., Lee, J. J. W., Chai, H., Zipfel, B., Ziscovici, C., Lawn, B. R., & Lucas, P. W. (2010). Tooth chipping can reveal the diet and bite forces of fossil hominins. Biology letters6(6), 826-829.
  4. de Waal, F. (1986). The brutal elimination of a rival among captive male chimpanzees. Ethology and Sociobiology7(3), 237-251.
  5. Wood, B., & Lieberman, D. E. (2001). Craniodental variation in Paranthropus boisei: a developmental and functional perspective. American Journal of Physical Anthropology116(1), 13-25.
  6. Strait, D. S., Weber, G. W., Neubauer, S., Chalk, J., Richmond, B. G., Lucas, P. W., … & Smith, A. L. (2009). The feeding biomechanics and dietary ecology of Australopithecus africanus. Proceedings of the National Academy of Sciences106(7), 2124-2129.

25 thoughts on “The human face evolved to take a punch? Spoiler: no

  1. I wonder if this is aligned with a trend I’ve noticed in entertainment media. A big complaint I have with the most recent Batman movie and the most recent Superman movie is how they seem to boil down to fisticuffs movies. Batman, the expert martial artist and gadget-user, deals with Bane by punching him a lot. Superman also gets into a slug-fest with his opponents.

    Not long ago, Real Steel gave us boxing robots, and more recently, Pacific Rim teaches us that the way to fight big giant monsters is to build big giant robots (that require people inside them, never mind drone technology) who wade into the fight and punch the monsters.

    Talk about a WEIRD concept…

    • Oh he brings it full circle! It would certainly be interesting to see how widespread fisticuffs are. Do hunter-gatherers suffer from a lot of punches to the face?

      • My uninformed guess would be no. Boxing seems to have been invented by the Brits around 300 years ago, but it’s viewed as a descendant of personal combat sports in general. The Greeks seemed more into wrestling and racing, so it’s possible the idea of hitting people in the face is a fairly recent invention. In particular, personal combat seems to be more a sport except when applied to war or self-defense.

        • That’s really interesting. Given that they were looking at violence between people, I had assumed that it would be a fairly primitive behaviour that might be present in many cultures. So everyone would get hit in the face a lot.

          I hadn’t realised just how much culture might influence how people fight, even in a fear-based scenario.

          • In fact, hitting someone in the face is (as I understand it) extremely painful, and you’re as likely to break your hand as you are to break someone’s jaw. The padded gloves in boxing protect the hands as well as the face.

            Martial arts, which greatly pre-date boxing, focus on striking the actually vulnerable (and softer!) parts of the body.

            No doubt personal violence is as old as, well, persons, but I think boxing is more for show and sport than being a valuable fighting tool.

  2. Perhaps the female australopithecus just found the robust males more attractive than the thin-jawed ones and favored them as sexual partners. One can come up with plenty of hypothesis, the problem is to figure out the full range of consequences that a particular theory will have, and to make sure that this theory is consistent with all (not just some) of the available archeological evidence (and much better so, than other hypotheses). Turning the problem around a bit – what key evidence is missing in the current archeological record that prevents you from supporting the diet-theory fully, i.e., what should one look for or hope to find in order to prove or disprove it?

    • There are a lot of potential explanations; plus it’s likely more than one is true. Biology is messy and there are often multiple factors driving the development of something. The evidence does suggest that the dominant factor is diet, but there may well be other ones playing a small role. Maybe sexual selection, maybe even fighting.

      When trying to figure out which are valid, simply coming up with something that is consistent with the evidence isn’t enough. It needs to be able to predict the discovery of new evidence and have it’s basic assumptions vetted by external sources (i.e., not just examination of anatomical traits). Looking for evidence of injuries caused by fighting would be an external check of the face-punch idea, for example.

      As for diet, the gold standard is isotopic analysis and microwear. Gathering as much data in these areas would be a great way to test it; but sadly not every fossil can be analysed by these means. Fossils which spend a significant amount of time on the surface, for example, become damaged making it hard to examine microwear to work out diet. How to distinguish between regular damage and dietary damage? When such studies can be done they vindicate the diet idea (although there are a few surprises here and there); but more data is always better.

      • What isotopes are used for tracing diet? Would a diet based on soft leaves differ from one based on hard roots even if the same plant was involved? What about regional and/or temporal variations in the isotopic composition, could they mask or be confused with differences in diets?

        • Carbon (12C and 13C) and nitrogen (14N and 15N) are the isotopes most commonly used to investigate diet, with the former being the ones typically applied to really old fossils.

          It can’t distinguish between different parts of the same plant, but can tell the difference between different kinds of plant (C3 v C4). These could then be cross-referenced with pollen records from a site to see which examples of those kinds of plant exist. In the case of Paranthropines, it was discovered they eat C4 plants. The C4 plants in their environment were grasses and sedges. As I said though, you can’t tell which part of the plant they were eating. That’s where microwear comes in.

          This is particularly useful because most of the C4 plants are hard/tough. Be they grasses, nuts, or have most of their nutrition in roots/tubers. So identifying if they ate a lot of C4 is a good step in figuring out if their diet would have necessitated their weird face.

          Isotopes are different for different times and places; which is why it’s important to also examine local fauna also recovered from the site to get a baseline. If we know that a particular type of gazelle eats a certain kind of plant, looking at their isotopes can tell us what the signature of that plant looks like, for example. Again, here micorwear is good as it can double check whether these herbivores were eating what we thought they were eating. This cross-checking is also important as there tends to be a lot more faunal fossils; so provide a more diverse picture of what the foodscape was like.

          Phew, that was quite long. I hope I managed to answer some of your questions in there.

  3. The key thing to realize is that humans are not well-endowed with natural protective features – such as horns or a mule-kick. The hand has clearly evolved to be able to punch any attacker with the minimum danger of self-injury. The shape of a clenched fist helps to minimize the possibility of damaging the fingers, with special arrangements to protect the thumb.

    The evidence is looking very much as if early humans split into a number of distinct groups which could still interbreed (for example us, the Neanderthals and the Denisovans) and different lines could well have different ways of socially interacting, some possibly involving aggressive male interaction. In the circumstances one would not expect human facial bones to be particularly vulnerable to damage from a clenched fist.

    While I feel the paper has overstated its case it makes sense that a human head has evolved so the owner is not incapacitated by a single blow!

    • No doubt damage resistance has played a key role in the evolution of our skull; but it can’t explain the plethora of traits that emerged in these particular species, as the paper claims.

      As for punching, comments on this post by Wyrd have piqued my curiosity. After all, we’ve spent many years perfecting it and it’s prevalent throughout our culture; which raises the question as to just how innate it is. Do you know of any cross-cultural studies that look into whether punching is the preferred sort of unarmed combat amongst hunter-gatherers, for example? That would go a good way to showing that it is a behaviour we might expect our ancestors to engage in.

  4. I would have thought that face punching took off fairly recently when carrying weapons was deemed antisocial. This would occur with the appearance of sufficiently strong government to monopolise the use of violence and provide alternate mechanism for dispute resolution.

    Punching is a ritualised style of fighting causing loss of face as much as incapacitation and is unlikely to cause death by itself. Should I ever have the misfortune to find myself suddenly transported to the Palaeolithic and engaged in a life-critical resource dispute with another hominid, my preferred offensive option would the use of a projectile weapon. Failing that, the use of a suitably solid stick to hit my adversary sounds a better strategy than engaging in a face punching competition.

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  6. I don’t know if you have ever heard of the Youtube channel “SciShow” but they just did a video about this topic:

    I posted a link to this blog post- I hope you don’t mind!

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  9. Pingback: Does buying your date dinner work? (or, “the second big reason you shouldn’t trust evolutionary psychology”) | EvoAnth

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