In their critique of the article reporting evidence for alleged cannibalism at site 5MT10100 near Cowboy Wash on the southern piedmont of Sleeping Ute Mountain, Kurt Dongoske, Debra Martin, and T. J. Ferguson challenged many of the conclusions and lines of evidence presented in the article. Among these was the evidence of consumption of human flesh from a coprolite found in a hearth at the site, which could potentially serve as the “smoking gun” offering physical proof of cannibalism, if the analysis is correct. The authors of the critique found the presentation of this evidence in the initial article unconvincing, however, describing the data as “sketchy” and implying a lack of scientific rigor in the analysis. They concluded this section of the critique by saying:
We are not microbiologists, and therefore before accepting the claim that the coprolite contains human myoglobin, we await peer review and publication of the fecal study by Science or another scientific journal specializing in biomolecular research. As presented in the Cowboy Wash study, the fecal evidence is suggestive but not convincing. More work pursuing this line of evidence is warranted in future studies.
In their response to the critique, the authors of the original paper added more detailed information on the coprolite analysis, but they also did as the critique authors recommended and published a short article in Nature (Science‘s main competitor) giving more specific details on the analytical techniques used to detect human myoglobin both in the coprolite and on some potsherds from a cooking vessel found in the same pitstructure. There isn’t actually much in this paper that wasn’t in the response to the critique, aside from the laboratory procedures, which I am not in a position to evaluate. It’s not actually clear to me if this article was peer-reviewed; it doesn’t explicitly mention any reviewers or any details of the review process, but this doesn’t necessarily mean it wasn’t reviewed. It’s also not clear to me if the authors submitted it in response to the critique or if they had already intended to. Both the original article and the critique were published in January 2000, and this article was received by Nature on March 7, accepted on June 6 (which does seem to imply some sort of review process), and published on September 7. Meanwhile, the response to the critique was published in April. In any case, whether or not the authors of the initial paper were spurred by the critique to submit additional publications (and this is not the only one to appear after the critique was published), they certainly can’t be accused of shrinking from the challenges it set for them.
Mentioning this paper also allows me to go into a bit more detail about the myoglobin analysis, which I didn’t in the previous post. Basically, to determine if the coprolite resulted from the consumption of human flesh the researchers needed to find something to test for that would be present in parts of a human body likely to be consumed but not in parts of the consumers body likely to end up in the coprolite during the digestion process (e.g., blood or intestinal lining). They decided on myoglobin, which is a protein molecule in the skeletal and cardiac muscles that transports oxygen from the outer membrane of muscle cells to the interior parts of the cells where it is used to generate energy. Importantly, this protein is not found in the smooth muscles of the digestive system or in the blood, so it is unlikely to end up in fecal matter as part of the digestive process. The researchers used a variety of controls to establish this, including coprolites from Salmon Ruin and modern fecal samples from “normal individuals,” people with blood in their stool, and people who had recently eaten beef. None of these ancient or modern samples tested positive for human myoglobin, but the beef ones did test positive for bovine myoglobin, establishing that myoglobin can indeed be found and identified to species in fecal material. These controls were mentioned in the original article, and when I read it I had wondered where they had gotten the modern samples. The Nature article explains that they came from leftover material from clinical samples that was turned over for research use, which makes sense. For the sherd testing, the controls were other sherds from the same site, sherds from another site in Southwestern Colorado dating from the same period but without evidence of cannibalism, and sherds from a Plains site near Denver also dating to roughly the same period. None of these control sherds tested positive for human myoglobin either, although some tested positive for deer or rabbit myoglobin. Thus, since the coprolite from Cowboy Wash and the sherds found near it were the only samples to test positive for human myoglobin, the hypothesis that they were associated with ingestion of human flesh was not disproven, and it remains the most plausible explanation of the Cowboy Wash assemblage.
It’s certainly possible that problems may be found with this analysis that cast doubt on the result, but I haven’t seen any, and until I do I’ll provisionally accept it as indicating very strongly that broken and burned bone assemblages like the one at Cowboy Wash most likely result from cannibalism. What that might mean culturally and historically, of course, is a different and more difficult question.
Marlar RA, Leonard BL, Billman BR, Lambert PM, & Marlar JE (2000). Biochemical evidence of cannibalism at a prehistoric Puebloan site in southwestern Colorado. Nature, 407 (6800), 74-8 PMID: 10993075