Saturday, May 14, 2016


Hammerstone below petroglyph
panel, Wild Horse Draw, Canyon
Pintado, CO. Photograph 
Peter Faris.

On January 17, 2010, I posted a column on, Petroglyphs - Direct Vs. Indirect Percussion? In this I argued that most, if not all, petroglyphs had to be created by direct percussion and gave the reasons for this belief. I was recently informed by James D. Keyser of a paper that he and co-author Greer Rabiega published in the Journal of California and Great Basin Anthropology, 1999, Vol.21, No. 1, pages 124 - 136, entitled Petroglyph Manufacture by Indirect Percussion: The Potential Occurrence of Tools and Debitage in Datable Context. Keyser's comments concerning examples of indirect percussion are well reasoned and quite convincing, and are based on experiments reproducing fine or narrow lines on stone by striking a "chisel stone" with a hammer stone.

Rock art on boulder,
Airport Hill, St. George, UT.
Photograph Peter Faris, 2002.

Hammerstone on boulder,
Airport Hill, St. George, UT.
Photograph Peter Faris, 2002.

In his e-mail to me Keyser stated :

"I just look for the evidence, and where one finds very precise dints repeatedly aligned with one another to form all or part of a design the chances are that that design (or the very precise part of it) was produced by indirect percussion. Very finely made antlers (and other extremities) on small images of deer in Valcamonica rock art are a good example, but there are many others. Most often the examples of this sort of work that I can think of off-hand are small parts of  larger figures (but the entire figure itself is still not very large—say a deer that can be covered with a playing card)." (Keyser 2016)

"When a small part of a glyph occurs routinely (like the aforementioned Valcamonica antlers) without even one misplaced dint it begins to defy statistical probability that these were done freehand—when such a simple solution (indirect pecking) was available and can provide a guarantee that no dint will be miss-hit. If such finely produced antlers were relatively rare—so that there were a few of many that had no miss-hit dints, then one could argue that the very precise ones were simply normal variation, but when one sees dozens of examples of such deer at site after site—all of whom have antlers, legs, hooves, and open mouths—with nary a miss-hit dint in the bunch—a student must begin to look for a way that this was done that essentially “guarantees” accuracy EVERY TIME THE STONE IS STRUCK. Indirect percussion is the only means by which this can be accomplished (with such a guarantee) that I can come up with....I’d be glad to know." (Keyser 2016)

Hammer stone used with chisel
stone in experiments showing
evidence of impact with the chisel
stone on its side. (Keyser , James
D., and Greer Rabiega, 1999).

I am actually more convinced by what he did not find than by what he did. Keyser reports large numbers of fine lines in petroglyphs with no evidence of the mis-strikes that one would expect to find if only direct percussion had been used to produce them. Now this is a telling argument and I take it very seriously as I have to agree with Jim that the lack of missteps is suggestive of an accuracy very difficult (I am sure he would say impossible) to achieve with only direct percussion.
I do feel compelled to note, however, that this paper and communication are both about an experiment, and that he has not yet reported finding such chisel stones. Admittedly, there has probably been little awareness of their possibility so no one has looked for them. Also, Keyser also commented that as they are smaller and lighter than the hammer stones they may have regularly been carried away as useful tools, not dropped in the ground when the petroglyph is done as so many hammer stones were, " that’s the beauty of a chisel stone—you can carry two or three dozen of them with the same weight as a single good-sized hammer stone." (Keyser 2016)

Bird Rattle carving petroglyph,1924,
Writing-on-Stone, Alberta, Canada.

I am enclosing this picture of Bird Rattle producing a petroglyph at Writing-on-Stone, Alberta, Canada, in 1924, as it is the only illustration I could find of petroglyph production in an authentic context. It really does not apply to the question here, however, as this petroglyph was produced by incising, not by pecking, so the techniques under discussion were not used by Bird Rattle.

Bird Rattle carving petroglyph,1924,
Writing-on-Stone, Alberta, Canada.

Note: until such a chisel stone is reported in context at a petroglyph site this is all conjecture based only upon logic and his reported experiments, but then my original statement was also. Remember, the absence of proof is not proof of absence. So, thank you to Jim Keyser for his information and help. I appreciate that you took the time to help me clarify this question. Correction noted Jim, and thank you. I will temper my opinion accordingly. 
And I also must confess that I have never examined the fine lines in a petroglyph for this phenomena, superimposition yes, mis-strikes no. So in the future I will have another line of evidence to look into. 
Those who would like to dig a little deeper into this example are referred to the 1999 paper by Keyser and Rabiega, cited below.


Keyser, James D., personal communication, May 7, 2016.

Keyser , James D. and Greer Rabiega,
1999,  Petroglyph Manufacture by Indirect Percussion: The Potential Occurrence of Tools and Debitage in Datable Context, Journal of California and Great Basin Anthropology, Vol.21, No. 1, pages 124 - 136.

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