By John C. Whittaker and Devin Pettigrew, published in The Atlatl 2023.04 (images available in that newsletter)
We have had people ask why we would bother to continue doing carcass experiments, sort of an “if you’ve shot one bison, you’ve shot ’em all” attitude. Any hunter or experimenter knows this is not the case. In experiments with many variables, you need many trials to test the different variables and to reduce the effects of random errors.
Prehistoric hunters did not have the tools we moderns use to observe and understand many complex variables at once, but still built up years of their own and others’ hunting experience to discover what worked best. Even in modern experiments, we test new ideas and observe the effects of small changes that improve our understanding or become the basis for further experimentation.
For instance, in testing stone point penetration, one of the things we continually notice is the importance of carefully-crafted hafting of the shaft, especially in seating different forms of points in appropriate foreshafts (Figure 1). This is one part of the enormous amount of work required to prepare for one of these experiments: weeks of gathering points, hafting them, documenting them with measurements and photographs, and organizing the rest of the projectile arsenal and recording equipment. Pettigrew did almost all of this work, with the exception of making the points, which came from a number of knappers, including Whittaker (Figure 2).
For the bison experiments, so far we have made a total of 272 shots with darts and arrows and used a total of 169 knapped points mounted on separate foreshafts. We previously performed bison carcass experiments on a 23-year-old cow in 2020 and a 2-year -old bull in 2022 (see Whittaker and Pettigrew 2020; Pettigrew et al. 2023).
In July 2023 we performed a third bison experiment, the focus of this article. Finding an animal and a place to work is another of the logistic problems of naturalistic experiments. This bison was one of a herd raised for meat by Eagle’s Wing Ranch in Colorado (eagleswingnaturalbison.com). The two-year-old male, weighing 900-950 lbs, was humanely killed by the helpful rancher, Jim Beauprez, immediately before our experiment.
We set it up resting on its belly, legs tucked under, as close to a natural resting posture as possible Figure 1. Hafted Clovis point, dyed with methyl violet. Figure 2. Some of the dart points we used, shown here after the experiment, Figure 3. Experimental set-up. 2 (Figure 3).
As in our first experiment (see The Atlatl Fall 2020), we used two high-speed cameras to record throws, but this time we switched the roles of the two cameras. The Casio EX-F1 was set close to the thrower and aimed at the bison to record the flight and impact of the darts at 600 frames per second, while the more powerful Chronos 1.4 camera recorded the impact of the dart or arrow from near the bison and perpendicular to the flight path at over 3000 fps.
Each projectile point was individually hafted on a foreshaft and fitted to one of several mainshafts. In addition to other photos and measurements, all hafted points were photographed for 3d modeling before use, and the points were dyed with methyl violet to make damage more visible (Figure 1). After each impact, the location of the hit was photographed and the depth of penetration and any other observations of damage to the point or bison were recorded. The skeleton is currently being cleaned by Artworks Taxidermy (Broomfield, CO) for analysis of impact damage and butchering marks on the bones.
Figure 4 shows the kind of data produced by the cameras: a screen capture from the Tracker video analysis program showing a shot with the Clovis point shown in Figure 1, which penetrated towards the back of the thorax. The auto tracker function in Tracker works to automatically place velocity markers over the reflective targets on the dart shaft, removing subjectivity from placing them manually (a big improvement allowed by the higher resolution of the Chronos camera). The video is calibrated using the camera’s frame rate and a scale placed on the dart shaft.
For this shot, and many others like it, the most rapid drop in velocity (upper graph, y-axis) occurs as the point penetrates the skin. The x-axis tracks the distance of the penetration event in meters, with zero set to the moment of initial skin contact (configured via placement of the pink axis). The acceleration data (bottom graph) shows two high peaks in deceleration: The first begins as the skin stretches on impact and the point begins cutting through it. This peak reaches its climax when the haft area pushes through the skin, ca. 10 cm into the carcass. The second peak occurs deeper in the carcass, ca. 46 cm, and probably indicates the moment when the point hit the skin on the opposite side of the bison. At this juncture, penetration ceased and the remaining velocity and acceleration values reflect vibration of the dart shaft.
Although this dart struck with a whopping 106 Joules of kinetic energy, by the time it encountered the opposite wall of the torso it retained only 15 J. Most of its energy (ca. 60 J) was used to penetrate the hide. Points that were more efficient at penetrating hide lost less energy, but also tended to be less durable when impacting bone.
We focused on heavier darts (ca. 200-350 g) in this experiment than with the first bison. This was good, because impact forces to cut through skin in this experiment were also higher. In many shots, clouds of dust can be seen in the high-speed video when the points cut through the outer hide. Pettigrew took a 20x20cm piece of skin, washed it, and soaked it in water to remove the wool. Once the sediment settled and the water evaporated, and the wool slipped from the skin and was dried in the sun, this resulted in 20g of sediment and 40g of wool from the skin.
So unlike the previous two experiments, the bison still had most of his winter coat, which clearly had a lot of sediment embedded in it. This seems to have formed a substantial barrier to penetration, and probably the reason for a lot of the bounces we experienced. Like the previous bull, the skin itself was ca. 4 mm thick. Darts that were able to penetrate the skin but struck the shoulder continued to experience high impact forces and were unable to penetrate beyond the shoulder, unsurprisingly.
Many darts cut the edges of ribs and continued on into the animal, but those that struck bone directly were often severely damaged or broke their hafts, and only one shot broke a rib. But darts that cut through skin and penetrated into the thorax or abdomen of ten penetrated significantly into the body cavity, stopping at the skin or ribs on the opposite side of the torso. Unlike in our previous two experiments, no darts penetrated all the way through this bison, but 30-40 cm of penetration was common, surely killing shots in a hunt (Figure 5).
Kinetic energy is what allows a dart to cut through and penetrate a solid target, but excellent dart mechanics, including straight flight, strength, and sleek ness of the shaft, are also key to achieving lethal penetration. The sharpness of the point and durability of the haft are also crucial.
Our Tracker analyses indicate that the most substantial deceleration often occurs when the haft area encounters the skin after the point has entered. This demonstrates that hafts that are both aerodynamic and strong are essential for hunting big burly animals. These factors may outweigh really high kinetic energy for dart lethality. Haft damage, haft failure, and points that were not sufficiently durable and sharp resulted in several shots that bounced or achieved only shallow penetration.
The thick layer of dirty wool was a substantial barrier for imperfect points and foreshafts (Figure 6). Any crevices between the point and its foreshaft notch caught on the wool. On some shots we could see that wool had been pulled into the wound. Careful application of pitch around the end of the foreshaft to make a smooth transition between point and shaft was important. When the pitch ramps became damaged after the first shot, penetration could drop or the point simply bounce out on the Figure 4. Tracker screen-shot of a throw with the Clovis point in Figure 1. Figure 5. Measuring penetration – 29 cm with this point. 3 next shot. We used the usual ~50% pine resin to 25% each of ground charcoal and elk droppings for this mix. Stronger pitch mixtures are something to look into. Thinking about quality of the points and hafting also leads us to reflect on some of our ideas about prehistoric technology.
We should expect that hunters who relied on their weapons for survival would become expert at making them, and indeed some of the prehistoric atlatl finds from the SW are very well crafted. Another example might be the Inuit Arctic technology in early historic times, where hunting gear, clothing, and other technology is among the most sophisticated and carefully built you can find anywhere. On the other hand, it is easy to notice that stone points all across the continent are made with many levels of skill, from crude and ugly to masterpieces of delicate work. So we can’t expect that all prehistoric equipment was equally well-made, and perhaps we should test some examples that are not so good as well some made to our highest standards.
It’s important to note that our results are not necessarily representative of all prehistoric equipment through millennia of human history, and we are still learning. Nevertheless, our experiments on different carcasses show that the target has a dramatic impact on how well any given projectile will function. Hunting big animals like bison would certainly create a strong impetus to optimize one’s atlatl and dart equipment, and it is certainly feasible for smart and skillful hunters to routinely kill large animals with well-designed atlatls and darts (Figure 7).
The team for this experiment included
- the authors
- *Donny Dust (https://www.donnydust.com/)
- Bobby Marshall (https:// www.themountainsidepodcast.com/about)
- Autumn Cool
- Marissa Crise
Flintknappers who made points for the bison experiments included
- the authors
- Adam Lageveen
- Brian Sortino
- Donny Dust
- Ed Mosher
- Evan Phillips
- Gary Morgan
- Gerald Pettigrew
- Jake Webster
- James Parker
- Jim Schroeder
- Kevin Verhulst
- Mike Evans
- Silas Chapman
- Steve Saffold
- Tom Mills
- Tony Soares
- William Harrison
- Zack Hansen
Pettigrew was recently interviewed by Marshall about the experiments for The Mountain Side Podcast (episode 136).
*Whittaker, John C., and Devin Pettigrew 2020 Atlatl vs Bison. The Atlatl 33(4): 1-4.
*Pettigrew, Devin B., Justin Garnett, Caden Ryals-Luneberg, and Eric A. Vance “Terminal ballistics of stone-tipped atlatl darts and arrows: Results from exploratory naturalistic experiments.” Open Archaeology 9: https://doi.org/10.1515/opar-2022-0299