Friday, January 15, 2010

Prehistoric ballistics, or Mythbusters meets archaeology

Nicole Waguespack and a bunch of others (including four of the Mythbusters gang, which leads one to wonder whether this will be the basis of a future episode) ask the question: "Given that so many hunter-gatherers use/d stone-tipped projectile, what are the advantages of a stone tip relative to one whose point is simply sharpened wood?" ResearchBlogging.orgThis post was chosen as an Editor's Selection for ResearchBlogging.orgThis is a good question to ask, since crafting an projectile point from stone consumes more time, effort and resources than simply sharpening the end of the shaft that you'll be making anyway. Hell, one could even argue that knapping a stone point incurs some additional risk since you risk slicing up your hand as you do so, as anyone who's ever tried their hand (eh!) at flintknapping knows all too well. These costs are all the more important to keep in mind given the frequency at which stone points break during use (Waguespack et al. 2009:787).

As the authors argue, it's generally assumed that stone makes for a more effective projectile point, though this has rarely, if ever, been tested empirically. As they state:

"Numerous ‘common knowledge’ explanations appear to be generally accepted regarding the superiority of stone, and to a lesser extent, osseous point tips relative to sharpened staves (e.g. Guthrie 1983; Arndt & Newcomer 1986). Assumptions concerning performance (e.g. durability of the tip), lethality (e.g. length of cutting edge, depth of penetration) and aerodynamics (e.g. weight distribution, flight paths) abound. Unfortunately, few of these assumptions have been verified experimentally (Waguespack et al. 2009:787)."

To test whether stone is actually more efficient, Waguespack et al. (2009) (available as a free pdf here)made replicas of six wooden and six stone-tipped arrows and shot them at a human torso-shaped block of ballistic gel, draping it with caribou hide in some cases to simulate the arrow having to pierce the thick skin of some animals. They conducted two tests. The first, designed to see whether stone and wood tips penetrate a target more or less deeply, had the arrows shot from a compound bow 1.1m away from the target. The second, designed to see if the two types of arrowheads have different degrees of accuracy, had the arrows shot from the same contraption but at a distance of ca. 16.75m.

Picture of the experimental set-up used by Waguespack et al. 2009.
(from Waguespack et al. 2009: Figure3, p. 794.)

The results of these experiments indicate that both arrow types bestow equal degrees of precision to their users and, most importantly, that stone-tipped arrows provide only marginally higher degrees of target penetration (about 10% more), especially considering that both arrow types penetrated more than 20cm into the target. These observations lead the authors to conclude that the benefits of using stone-tipped arrows probably do not make up for the extra time, resources and risk involved in making them. Therefore, they argue, it is likely that the ubiquity of stone tips is driven by some other consideration, either other parameter of hunting effectiveness or social dimensions of projectile point making, such as the prestige derived from skillful stone working.

While there is some ethnographic evidence for the functional argument (e.g., Ellis 1997), Waguespack et al. (2009) provide a good discussion of why stone points are effective conveyors of social identities and/or a form of costly signaling. Costly signaling basically refers to behaviors that are not strictly functional but nonetheless serve to augment the social standing of the people able to effectively engage in them, be it through more finely honed skills or access to resources unavailable to others (or their profligate use).

Currently having lithics on the brain since I'm preparing to teach my Lithic Analysis seminar this coming terms (there's still some open seats if you're an interested student living in Colorado!), I thought this was a really good study that yields both interesting results and a powerful demonstration of how experimental archaeology can help answer long-standing anthropological questions (and, in this case, in a manner appealing to a wide audience!). With that in mind, I was nonetheless left wondering whether results might have differed if other types of projectiles had been used (e.g., darts propelled using a spear thrower, or hand-cast spears or javelins). Likewise, I would have been really interested in seeing the penetration results of both point types in the accuracy experiment, since 16.75m (ca. 50 feet) is likely to have been a more appropriate prey-hunter distance approximation than 1.1m (ca. 4 feet) used in the penetration experiment.

In any case, if the authors are right, this opens up some really interesting avenues to research technologically-mediated costly signaling in the deep past. Since stone points were used as far back as the Middle Paleolithic and Middle Stone Age (ca. 300,000 years BP), it implies this practice may be quite old. In sum, this paper provides a good theoretical and empirical basis to ground studies of costly signaling as reflected in some classes of chipped stone implements (i.e., points) which are certainly better in that respect than handaxes, as I've discussed recently.

Update: Turns out this episode already aired a long time ago, on Feb. 13, 2008 to be precise. That's what I get for not having cable, let alone a TV!


Ellis, C.J. 1997. Factors influencing the use of stone projectile tips: an ethnographic perspective, in Projectile technology (H. Knecht, ed.), pp. 37-74. New York, Plenum Press.

Waguespack, N.M., Surovell, T.A., Denoyer, A., Dallow, A., Savage, A., Hyneman, J., & Tapster, D. (2009). Making a point: wood- versus stone-tipped projectiles Antiquity, 83: 786-800


Sol said...

I don't know if it's necessary to immediately jump to the "non-functional"/"prestige" explanation in this case. I can think of a few possible explanations to justify the effectiveness of stone-tipped projectiles over sharpened wood (though none of these are backed up by anything more than "common sense," which as we see here is the reason for the problem in the first place):

a) the use of sap to adhere the stone point to the stick acting as a poison (although, of course, a stick from the same tree could also be poisonous)

b) a stone point might snap off inside flesh more easily, causing more tissue damage (but again, this would need to be tested, plus the loss of the point would have to be weighed against the gain of the increased tissue damage)

c) this might be complete nonsense, but otherwise useless detritus from tool production could have been used as points, which wouldn't have taken all that more energy to do since the detritus was just lying around anyway

... and I'm sure there are lots of others. All those points can pretty easily be refuted - I never claimed to be an expert. Still, it's a really interesting study, and it shows that things we take for granted are often taken unjustifiably, but this is anything but "disproof" of the efficacy of stone vs. wood.

John Hawks said...

I had always understood the functional explanation to be twofold:

1. The same as for modern bowhunters who use wide razor points instead of small target points: bloodletting.

2. The probability that a wooden projectile will pull out as the animal runs away, versus a stone which may break off and remain to make the wound more severe.

The paper discusses number 1 briefly, and their experimental artifacts surely show the potential -- those stone points would make a cut three times the size of the sharpened wood points. I'd call it a myth too, since I've never seen anybody really test it with stone points, but it is consistent with modern bowhunters.

Jason Woertink said...

I wonder about instances when it is used against targets without tough hides, like other people. Perhaps the stone is better at killing people rather than animals.

Julien Riel-Salvatore said...

Sol -
you make some good points (ha!). From the literature I'm familiar with, poison was usually applied to organic (mostly bone) projectile points designed to detach from the shaft to which they were bound. In this case, binding would be a secondary consideration and if poisonous resins were used, their effectiveness might be somewhat impaired by the fact that they were often treated by fire or cut with other materials to make it less brittle (e.g., ochre), or bound with additional ligaments such as sinews or string.

The observation that stone causes greater tissue damage (and greater bleeding, as John argues) is well demonstrated empirically. To be fair, however, Waguespack and colleagues only tackle the dimensions of penetration depth and accuracy in their experiment, and acknowledge that they can't really address greater lethality on the basis of their results.

As for using debris, that's a strategy that's been documented in projectile weaponry composed of serially mounted segments. I think that for points sensu stricto, shaft parameters and aerodynamic consideration somewhat limit the usefulness of unretouched debris as potential tips.

With all that said, you're correct in asserting that the paper doesn't disprove the effectiveness of stone tips as a whole. However, insofar as it provides solid empirical data to narrow speculation about what may make stone more effective given its higher costs, I think it's a very useful contribution to the literature.

Julien Riel-Salvatore said...

John -
you make an interesting observation about bloodletting and the size of cuts made by stone points, some of which echo Ellis' arguments. As I mentioned in my response to Sol's comment, the paper really seems geared more towards some of the other (largely untested) assumptions about what else might make stone a better material for point manufacture. I think it's a first step in the right direction... though I'd certainly like to see what the Mythbuster gang might come up with as targets to test the bloodletting hypothesis! Undergrads in need of extra credit perhaps? ;)

Julien Riel-Salvatore said...

Jason -
the paper presents some results based on penetration in the target in the absence of hide. Basically, the tendency for stone-tipped arrows to penetrate slightly deeper than wooden ones holds, with the authors even stating that "both types types of points in some tests managed to penetrate the entire thickness of the ballistics gel torso" (Waguespack et al. 2009: 794). Based on these results, both wood and stone seem equally good at killing people, at least under these experimental parameters.

Sol said...

How about non-flesh wounds? This just occurred to me, but given that the arrows in the study could penetrate the ballistics gel torso (which never fails to illicit hoots and holloers from the Mythbusters team), are arrows capable of breaking or at least harming bone, or at least some of the tougher parts of the body, like cartilage (for example, the floating ribs, which I imagine if penetrated would cause some real damage)? If this is the case, particularly when used by an expert hunter, stone-tipped tools might be much more effective in the over-all goal of bringing a large mammal down than sharpened wood, even if their penetrative advantage is negligible.

amphiox said...

I think it is in fact important to know if the results would be the same for thrown spears/javelins and thrusting spears.

Because thrusting and throwing spears were invented long before bows and arrows, then if a stone tip for these weapons were much more effective than a merely sharpened tip, then it could well be that a tradition developed around afixing a stone tip to your projectile weapon, and when bows and arrows were invented, the old tradition was simply transferred to the new technology.

Julien Riel-Salvatore said...

Sol -
that's an interesting question. The experiment doesn't seem to have really considered this variable, largely because it wasn't designed to do so. As I said in an earlier comment, I think this experiment is a good first step to understand the ballistic properties of various types of projectile points. But resistance to internal structures, including bones, would certainly be an important consideration. Given the penetration ability of both point types, I'd wager some serious money that a wooden point could also probably shatter or puncture certain bones, especially relatively brittle ones like ribs. However, I doubt that wooden points would leave the kind of 'slicing' morphology on ribs like that seen on Shanidar 3 (discussed on several other blogs, including John's). So far, I'm really liking this comment thread... it's highlighting a lot of potential future experiments that can (and should) be done.

Julien Riel-Salvatore said...

amphiox -
also a very interesting observation... I suppose this could be tracked archaeologically using some kind of cultural phylogenetic approach amplified by a consideration of raw materials as well as lithic reduction traditions. Of course, the aerodynamics of arrowheads are somewhat different from those of thrusting and hand-cast spears, as well as from those of darts, so these would also have to be factored in.

Paul said...

Stone "knives" created using the same flaking methods as with spear points were a necessity for skinning and gutting the prey. Could be that the stone spear points were used simply because they were produced from waste material created when making the knives.

Julien Riel-Salvatore said...

Paul -
good observation. In fact, many prehistoric points appear to have doubles as knives... it could be that wooden points would have been too functionally specific in certain contexts, and that this need for a polyvalent tools (especially for highly mobile groups) would have made the extra time and effort investment in producing stone tips more worthwhile.

Jason Bagley said...

I think it is important to remember than even animals shot with modern firearms rarely just drop dead and often travel long distances before expiring. The purpose of a point is obviously to allow maximum penetration. The sharp edges of a stone tip will now start to lacerate the surrounding tissue with each movement the animal makes, much more so than a simple wood tip would. The massively increased blood loss will dramatically reduce the distance an animal can travel before dying, and increase the likelihood the animal actually will die even if hit in an area not immediately fatal. The reduction in loss of kills would be a powerful counter to the additional labor invested.

Tom said...

I suggest you visit the website of the magazine 'Primitive Archer'. They have years of discussion on just these sorts of issues, and the forum members tend to be the sort of people who try out their theories. Plenty of both archers and knappers in that group.

Julien Riel-Salvatore said...

Jason -
increasingly blood loss to exhaust wounded prey would certainly have been an important consideration, and is likely to have played a role in the selection of stone vs. wood points overall.

Tom -
thanks for the tip, I'll definitely have to check it out!

onix said...

otzi (this thread is indeed compelling and productive) tells a thing, that is noted here once casually, with the suggestion of debris use. 'points doubling as knives'.
what otzi showed is they carried (!) amazingly small quantities of stone, in amazingly small implements. since u need to carry arrows for a bow anyways, perhaps that was enough motivation. to carry less.
(otzis 'knife' is no bigger then many arrowpoints). other points in the comments i agree with are: the bloodletting, the penetration of harder tissues, that wooden arrows tend to be easily removed (and animals are known (at least by me;) to try that on arrows), and that 10% extra change to immobilise a prey for the effort of shooting one arrow is still a whole lot when you hunt for bigger game.(for every ten times you shoot you get one extra mammoth) if you look at the neolithic arrows it is also quite obvious prestige plays a role, especially when they start imitating casts. the poison argument appears also valid, and is sth. i think is very fascinating, i recently read a thread somewhere, in wich someone proposed nearly all arrows could have been poisoned ( perhaps even that pre arrow man poisoned their darts). that thought stayed with me. so like who forgot the knowledge of firemaking/ poisonmaking.. .
what could also be interesting is when people adapt shaping to wooden points, either integrally with the shaft, or as an implement,
papua for example, carried a range of arrows with diverse points, i can see many reasons that would be telling , for example: point shapes that are exclusive for wood , shapes that predate stone use and have been examples for stone(and more usually osseous) variety. (ie. stone point efficiency might be prey specific) lastly perhaps also superstition plays a role, i thoroughly believe stone points would tend to be more effective, so why not them. except for actual penetration of harder tissue, perhaps it is also interesting that wooden points tend not to 'ricochet' well once they hit bone (horn, teeth). so its not even about the destruction of the hard material but the penetration achieved after being reflected from it perhaps.

thrand said...

We just did a Video Busting your myth of the Ancient arrows on season 6 episode 5 Viewers Special 2 please check it out on youtube. MythBusters Ancient Arrows Busted By Thrand and Eldgrimr.

Anonymous said...

i just watched this episode and would like to tell the guys of mythbusters could have made a few more ranged testing, they only saw it through the viewpoint of hunting were a direct shot is more used, but they forgot to see that arrows were used on wars as wells, and on wars the ballistic shot was more used than the direct straight shot, so on a ballistic shot a stone point would make it easier for the arrow to land with its sharp side pointing down, while the sharpened wood one would not so easily, needs testing tough.....

Anonymous said...

i just watched this episode and would like to tell the guys of mythbusters could have made a few more ranged testing, they only saw it through the viewpoint of hunting were a direct shot is more used, but they forgot to see that arrows were used on wars as wells, and on wars the ballistic shot was more used than the direct straight shot, so on a ballistic shot a stone point would make it easier for the arrow to land with its sharp side pointing down, while the sharpened wood one would not so easily, needs testing tough.....