Evolved Fists or the Best Weapons at Hand?

Photo: Mike Nelson, via Flickr (CC BY, 2010)

My most memorable punch in the face was a beaut. Back during my first year of studying karate, some classmates and I had met up for a little unsupervised sparring practice—never a good idea for novices. After an hour or so of this, my friend Eric and I were easing out of it with what was supposed to be an easy cool-down round when he, with a surge of enthusiasm, threw a left jab that popped me front and center across the chin, teeth, and tip of the nose. (So nicely placed.)

My eyes rolled up into my skull and a warm red blanket of numbness closed in from every side of my field of vision. My knees slowly folded, all resolve to support my worthless body gone. Fight over! My concerned friends looked on while I, on the floor, gingerly felt out whether there was any actual damage (there wasn’t… that time). The punch hadn’t been so much painful as deeply stunning, and it was probably a good ten minutes before I stopped feeling its disorienting effects.

Experiences like that one, not to mention the far more powerful punches in prize fights or even board-breaking demonstrations by martial artists, can inspire considerable respect for the prowess of the human hand as a weapon. They also inspired a widely publicized recent study by evolutionary biologists Michael H. Morgan and David R. Carrier at the University of Utah, who have suggested that while evolution was reshaping our hands to improve our ability to use tools, it was also shaping them to throw more effective punches.

It’s a clever speculation, and its authors don’t really offer it as much more than that. Perhaps it contains a kernel of truth worth further investigation. Personally, though, I find it unpersuasive on evolutionary grounds—and what the heck, on fighting grounds, too.

Ancient hands, questionable fists

The great apes and the tree-dwelling ancestors we shared with them had hands that excelled at prehensile power grips, which were essential for holding tightly to branches. Only humans, however, have hands with the dexterity for precision grips that can manipulate small objects between the tips of the thumb and opposing fingers. Grab a hammer: power grip; grab a pencil: precision grip.

Comparison of the external (A) and skeletal (B) proportions of the hands of chimpanzees (at left) and humans. From Morgan and Carrier, J.Exp.Bio. (2013).

What makes our precision gripping possible is that our hands have much boxier proportions than do those of the chimps and apes. Our thumbs are longer, more flexible, and proportionally stronger, while our fingers are shorter. Those dimensions started to emerge more than three million years ago, roughly around the time that our australopith ancestors started to walk on two legs. Given the huge survival advantages that came with tool use, biologists have long surmised that dexterity was the primary factor that drove evolutionary changes in our hands.

But in their paper in the January 15 issue of The Journal of Experimental Biology, Morgan and Carrier point out that our hand’s shape also allows us to do something else that the apes can’t: make a true fist. Only humans can curl their fingertips tightly into the center of the palm without leaving a space, and only humans can then buttress (fold and lock) the thumb across the first two fingers—an arrangement that turns our fists into hard, unyielding clubs.

Diagram of a fist.

This is no coincidence, according to Morgan and Carrier. In all the known species of great apes, males fight with one another for the opportunity to mate. Among gorillas and chimps this conflict can be brutal, and even the relatively peaceful bonobo males mix it up over females. That conflict should exert evolutionary pressure to make males better fighters. In the case of humans, the researchers posit, it could have meant that natural selection found a hand design that makes us simultaneously great tool users and punchers.

The fight is on

Carrier’s interest in the role of fighting on human evolution isn’t new. In 2011 he published a paper in PLoS ONE that argued male-male aggression in our ancestors might have created sexual selection pressure favoring taller men (and not necessarily taller women), because their height would have enabled them to strike downward more powerfully during fights. This new set of experiments, however, seems to have been inspired by a heated discussion with their biomechanics colleague Frank Fish, as noted in what is now one of my all-time favorite acknowledgments in a research paper:

We thank Professor Frank Fish for suggesting the null hypothesis with a wave of his fist and the exclamation ‘I can hit you in the face with this, but it did not evolve for that!’

Morgan and Carrier seem to have taken that as a challenge.

To test how much advantage the shape of the human fist gives fighters, Morgan and Carrier recruited 12 experienced fighters. They measured how much power the fighters could deliver with closed fist strikes versus open hand slaps from various angles, and how the force of a blow was distributed throughout the hand and wrist during impact. They also looked at what happened when the fighters struck with hands shaped into approximations of what primates’ fists look like. (If a chimp tries to make a fist, for example, its thumb juts out somewhat as shown in image C just below.)

The three hand postures studied by Morgan and Carrier: (A) a tight, fully buttressed fist, (B) a fist with tightly curled fingers but no support from a locked thumb, and (C) a fist without reinforcement from the fingers or thumb. From Morgan and Carrier, J.Exp.Bio. (2013).

How a fist changes shape during a punching impact (before: gray; after: black). A sturdy fist, as shown here, shows much greater stability than a more poorly shaped one does. From Morgan and Carrier, J.Exp.Bio (2013).

In brief, Morgan and Carrier documented that true fists do indeed make hand blows more formidable. Perhaps most notably, they showed that tucking the tips of the fingers directly into the palm doubled the stiffness of the middle finger’s knuckle during an impact—and reinforcing the fingers with the thumb doubled the stiffness again. That fourfold increase in stiffness not only makes the fist more clublike but could also reduce the tendency for the blow to hurt the puncher, because the reciprocal impact gets distributed throughout structures in the hand and wrist.

That general conclusion won’t come as a surprise to martial artists, who know from experience that a properly shaped fist can concentrate all the power of a punch into the small area across the top of the big knuckles of the index and middle fingers. (Japanese karateka refer to this hitting surface as seiken.) They also know that punching with an improperly shaped fist is an open invitation to injury. Nevertheless, it’s great that Morgan and Carrier have quantified some of these details, and I suspect that the findings about the effect of fist-shape on the stability of the joints will be one of the biggest lasting contributions of this paper.

Scoring the round

What, though, about their larger argument that natural selection was adapting our hands for pugilism at the same time it was making us dexterous? It’s not a preposterous idea, and I’d be interested in how further experiments by Morgan and Carrier (and more importantly, others) would explore it further. But the case seems weak and dubious to me for a variety of reasons.

A crucial test for Morgan and Carrier’s theory is precisely the argument that their colleague Frank Fish raised before their experiments began: can it distinguish fists specifically adapted for fighting from fists that we simply use when fighting because they are, well, handy. The late Stephen Jay Gould borrowed the term “spandrels” from architecture to account for features that look designed but are really happy accidents. Are our fists evolved weapons or just spandrels?

Without better knowledge about the constraints that might have influenced the shape of our hands, it is almost impossible to know. Evolutionary biologists often try to solve such problems by looking to the fossil record for signs that a feature’s function emerged over time. Morgan and Carrier haven’t done much of that kind of study yet, however: they discuss the shapes of apes’ hands and those of Australopithecus, but their work doesn’t report on the dimensions and fighting effectiveness of any ancestral species between them and us.

We also don’t yet know whether the modifications of fists would actually have provided enough of an advantage in practice to influence natural selection. Morgan and Carrier make the point that by striking with their seiken rather than their palm (shotei in karate), fighters can increase the stress on their opponent’s tissues by 1.7 to 3.0 times, thereby increasing the potential for injury at the point of contact. But the paper also acknowledges that open palm slaps exert about as much jerk (change in acceleration) on the target as punches do, and the level of jerk is what is most associated with traumatic brain and musculoskeletal injuries. So their argument depends on some assumptions about what kinds of inflicted injuries were most important in winning those fights for mating rights.

Remember, too, that even with their miserable fists, male gorillas and chimps can inflict devastating, even lethal injuries on their rivals. Yes, they are landing their blows with the immense strength of apes, but what they are hitting are other gorillas and chimps, which have a proportionate strength for taking a blow.

Nor is there much discussion in the paper about how apes, ancestral humans, and modern people actually fought. The paper mentions that punches are the most frequent blows thrown in mixed martial arts fights, and that babies innately raise their fists in anger, but those observations don’t really do anything to disprove Fish’s null hypothesis: that we use fists for aggression because it’s reasonably effective and easy for us to do.

Fists aren’t clubs

To me, there’s also another unacknowledged problem with their hypothesis. Contrary to what one might be led to believe from Morgan and Carrier’s measurements and the terrifying blows thrown in boxing matches and other sporting events, human hands simply aren’t great as bludgeons.

Example of a boxer’s fracture, shown by the broken metatarsal of the ring finger (at arrow). [Photo: Yayay, via Wikimedia Commons]

There’s a reason that fighters wrap their hands before a fight and put on cushioned gloves, and it isn’t all intended to reduce the brutality unleashed on their opponents. If you throw a full-power punch with an unprotected fist into someone’s face or head, there’s a very good chance you will break a finger or metacarpal (one of bones in the palm of the hand). Bones of the hand are fragile compared to the more solid bones of the skull.

Yes, you can break someone’s nose or knock out teeth easily enough, but if your opponent ducks his chin and your fist slams into the hard dome of his temple instead, you may be hurt worse than he is. Fierce punches to the body are relatively safer for your hands, but even then there’s a chance of slamming into an elbow and suffering what’s known as a boxer’s fracture—a break that can shove your knuckle halfway to the center of your hand. Left untreated, a boxer’s fracture can permanently impair someone’s ability to fight and grip a tool, so it’s not an injury to dismiss casually among our prehistoric ancestors.

John L. Sullivan, aka the Boston Strong Boy, last of the heavyweight champions of bare-knuckle fighting. (via Wikipedia)

In the heyday of John L. Sullivan and bare-knuckle boxing matches in the 19th century, fighters mostly threw snapping punches to the face and hard punches to the body until an opponent was an easy target for a knockout, which is why they adopted a fighting stance that can look a bit comical to spectators of modern boxing. My understanding is that the use of boxing gloves was introduced precisely to enable fighters to punch one another with full abandon: promoters liked that it made the fights more exciting… and never mind the harm done to the fighters along the way. This is part of why the incidence of serious brain trauma among boxers may have increased after the introduction of gloves.

(Bare-knuckle boxing hasn’t disappeared as a sport, by the way, though many of the surviving competitions may be of questionable legality, to say the least. I won’t link to any specifically because these fights can still be bloody and nasty, but search YouTube and you’ll find plenty of clips from fights. Consider yourself warned, though!)

The limitations of fists are why martial arts fighters often use techniques that involve the palm heel (shotei), the open hand’s knife edge (shuto), and the hammer fist (tettsui) for power strikes—all of which have their own advantages and disadvantages. It’s also why combatants in hard-fighting styles like muay thai often favor using elbow and knee strikes, because those parts of the body are even more devastatingly clublike than the hand can be.

I can’t help but wonder whether the new study’s selection of experienced fighters as participants might not be a methodological weakness. Experienced fighters know how to make good fists. Every martial arts teacher knows that instructing beginners on how to make a sturdy fist is one of the first challenges: new students often routinely put their thumbs inside their fingers, they stick out thumbs, they bend their wrists—all mistakes that undermine the fist strength that Morgan and Carrier measured. Martial artists benefit from centuries if not thousands of years of tradition on how to make good fists.

Would our ancestors stretching back to Australopithecus naturally make fists more like boxers or like children? If their punches weren’t strong, why wouldn’t they simply rely more on other blows and kicks? If evolution adapted our hands for punching, I wonder why it didn’t do more to increase the density or stability of our punching knuckles and finger bones? Or maybe evolution really did all that it could without impairing the even more important dexterity of our hands.

The problem is that we don’t know enough about the relative importance of different hand features to understand the constraints on their evolution—which is why this study, for me, loses by TKO.

• • •

Morgan, M. H. and Carrier, D. R. (2013). Protective buttressing of the human fist and the evolution of hominin hands. J. Exp. Biol. 216:236-244. doi:10.1242/jeb.075713

Carrier DR (2011) The Advantage of Standing Up to Fight and the Evolution of Habitual Bipedalism in Hominins. PLoS ONE 6(5):e19630. doi:10.1371/journal.pone.0019630

 

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11 Responses to Evolved Fists or the Best Weapons at Hand?

  1. John Rennie says:

    I’ve been much too slow in posting this piece, so I apologize for its lateness to whatever discussion there has already been about this research.

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  2. Jenna says:

    That makes plenty of sense. Other animals evolved improved appendages for fighting (antlers come first to mind) so why not us!

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  3. Cade DeBois (@lifepostepic) says:

    Given that slamming your fist into the face of another human, as that pic shows, is one of the surest ways for a human to contract a serious, incredibly painfully and potentially fatal infection–via the mouth of the other human, especially if we’re talking pre-dental hygiene hominids (seriously, primate mouths are nasty petri dishes!)–I say probably not.

    Curiously, this risk is lessen by one not being able to make a firm fist, like other primates, so you can’t cause as much damage to *your own self*. The higher risk of an infection via an open wound that allows nasty microbes that you likely couldn’t get any other way to access to your soft tissue and blood steam seems to make using one’s fist as a fighting tool, in addition to all teh various risks of serious fractures and soft tissue damage that could easily leave you in chronic pain if not with an unusable hand/wrist, seems like an evolutionary impediment, frankly.

    In the animal world, fighting done for courtship is often done with the intent to intimidate and only superficially wound the opponent at the most. It’s rarely to the death. The point is to breed, not die. Fighting for protection often requires a different set of skills, as well as a healthy dose of knowing when to flee. Likewise, most predators, although impressively armed, will err on the side of self-perservation–no point in taking down a rhino or a gazelle is you end up fatally wounding yourself in the process. Human aggression is quite different–it’s innovative, it’s adaptive, it does not solely rely on physiological evolution but also on a different tier of evolution: what we are able to acchieve through creativity.

    But of course, as is typical of humans, sometimes the solutions and ideas we come up with isn’t in our best interests. Chances are, we probably have been using our fists as weapons for as long as we have had them, because we needed something to hit the other guy with and it’s what we came up with on the spot. But it’s important to note we lost some of the evolutionary failsafes that keeps other primates from critically injuring themselves when fighting. For example, since we’re on this topic, we evolved much for sophisticated hands, which, thanks to our more sophicated use of them, we are both more dependent on them as well as far more prone to injure them, thus we must protect them more vigilantly than other primates. That suggest smart humans would protect their hands, while stupid one would use them as weapons. Additionally, in order to develop speech, we lost that impressive ability to scare to crap out of each other by baring a mouthful of fangs, and somehow words just don’t have that same visual impact when trying to intimdate an opponent before things get injurous. So we had to fall back on our creativity to compensate and thus we culturally developed so many rituals and stylized ways for fighting and combat, as well as weapons and armor. We likely figured out through trial and error (and various instances of deadly infected knucklebones) that simply punching each other was never in our best interests–and yet, we still do it. ‘Cos we’re pretty stupid like that. But at least we invented boxing gloves. Progress!

    But how did we evolved fists as we have? That is a good question. But I think evolutionary scientists like Morgan and Carrier need to think more broadly and with less bias than “What do men do with their fists?” Sometime, I swear, evolutionary scientists just assume masculinity is the sole driving engine behind evolution. But that’s another issue for another day…. Anyhow, if we assume that roughly 50% of any hominid population at any point in our evolutionary lineage wasn’t male, what female hominids do with their hands very likely had a big, big impact on our “manual evolution”. Likewise what communal activities male and female hominids did together probably was a hughely important factor too. Ponder that the next time you see someone “speaking” in sign language or gesturing while talking, or when you are writing something with a pen or pencil. More sophisticated communities would have needed more sophisticated communication, and that surely would have required more sophisticated tools, yes? And what would be more evolutionarily advantageous in that case, especially for a species what was developing an unprecedented capacity for creativity and social/psychological complexity? Using your sophisticated hands to grip a writing tool or to make a nuanced variety of communicative signs, or smashing it into some dude’s teeth?

    I’m not scientist, by the way. But I am a musician–guitarist, lutenist and pianist–and so I know quite a bit about how humans use their hands, not to mention a good deal about hand anatomy (it helped that my father was PhD of Human Anatomy and I grew up around his textbooks). It will take a lot more than this to convince me we evolved the ability to make a firm fist so to hit each as opposed to giving our hands more strength and vastly finer dexterity so we could do the many creative and communicative things we humans do.

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  4. John D Tribuna says:

    I would find it difficult to believe that in the millions of years over which human hands have evolved, there was one sole overriding use that guided their development. They’re the original Swiss Army Knife, muli-purpose tools adaptable to any number of seen & unforeseen needs or scenarios, from fighting, to inventing, to holding a baby.

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  5. David Rinker says:

    Interesting. However, self-defense web forums and instructors seem to think that we intuitively make a fist the wrong way. There is apparently only one way to make a fist correctly (i.e., in a way that doesn’t risk breaking hand bones) and lots of ways to make a fist incorrectly. Improperly formed fists risk severe, perhaps debilitating damage to the hand. How would this observation mesh with a model of optimization. Seems like if your a researcher focused on fighting ability as a selective pressure, the more parsimonious hypothesis would be that hand development was optimized for tool/weapon use and a concomitant move AWAY from bare fist fighting.

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  6. Mike McKelvy says:

    The extended hand with fingers locked straight is the most deadly configuration for the human hand. A well-placed blow by even a weak person under the jaw can kill any human. “there’s a kata for that”. The worst thing one might suffer is having permanent bends on the end(s) of the finger(s). Won’t affect the ability to grasp at all.

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  7. mpl says:

    Additionally, it seems a bit silly to think hands were significantly shaped to make fighting fists, when the same hands are so good at picking up rocks, sticks, sharp things, etc. Hands are too good at general purpose work to imagine special purposes were primary.

    I’m going to chalk this one up to super-adaptionist silliness.

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