Today in EvoLiteracy News: A recent study about the authenticity of the Shroud of Turin caught my attention for two reasons. First, it was published in Scientific Reports, a science-media outlet sponsored by Nature. Second, five authors believed to have tested two “hypotheses” when, in reality, they reconfirmed –indirectly– support for an old thesis (i.e. the Medieval origin of the shroud, 800 years ago) and speculated over a historicity-based idea (i.e. that the shroud originated in Jerusalem, 2000 years ago, and it was later transported to Turin). The study is an exemplar of conceptual error, and it can be used in scientific-methodology courses to educate our students on how to avoid making similar mistakes. – Guillermo Paz-y-Miño-C

Shroud of Turin, Poor Science, and the Persistence of a Myth

I will dedicate some length to examine this study (Uncovering the Sources of DNA Found on the Turin Shroud), which falls apart by itself when attempting to combine modern DNA analysis with a silly, pseudoscience project: to find scientific evidence to justify believing in a myth. The concerning part is that five authors, Barcaccia et al., were fortunate to publish the research (October 5, 2015) in Scientific Reports, a fairly known science-communication venue.

The team examined “two” hypotheses, one scientific, the other a historicity supposition. The scientific thesis –for which Carbon dating has provided unequivocal evidence since 1988/9— is that the Shroud of Turin is a fake, a fabrication of Jesus’ body’s imprint on ordinary linen traceable to the 13th and 14th centuries, specifically to 1260-1390 (C-dating is quite accurate). The historical supposition, in contrast, suggests that the shroud must have come from the years 30 or 33, of modern times, which makes it a 2000-year-old relict. The latter has no scientific sustain. But the authors build up –in a technical report format– the argument that their molecular analyses bring support to “both” hypotheses (Medieval origin and Jesus’ timeline). This is not the case. In fact, it is impossible to merge both proposals because the shroud is 800 years old, while the Jesus-person tale –if real– is three times older. Therefore, there is an irreconcilable mismatch in time between the two views.

Readers can judge the study for themselves (at this link), but I prefer to summarize the reality of its findings –while avoiding the authors’ convoluted logic– as follows:

First, Barcaccia et al. admit that the Carbon-dating piece of evidence –a crucial element in this case– demonstrates that the Shroud of Turin originates in Medieval times (statistical confidence 95 percent). That is, we are pretty sure that the linen does not come from 2000 years ago. The shroud is one third the age it is supposed to be under the historicity hypothesis. Therefore, everything else upon which the authors speculate in the study is irrelevant. The Barcaccia et al. conjectures, no matter how the investigators spin them, are inconsistent with the Carbon-dating clock: 800 years old.

Second, the shroud is contaminated with plant material (particularly pollen, which can be detected via chloroplast DNA analysis) belonging to plant species from, almost, all over the world (see figure below). Because the shroud’s linen is 800 years old, the contamination must have occurred during recent times.

Third, the linen of the shroud is also heavily contaminated with human DNA (detected via mitochondrial DNA profiling; see figure below), which belongs to multiple individuals, from multiple ethnic backgrounds and, therefore, from multiple geographic locations (Europe, West Asia, Northeastern Africa, Arabia, Middle-East, all the way down to India –not from the Americas). Again, because the shroud is 800 years old, human contact with it must have occurred during recent times.

Fourth, and this is not a trivial finding, although the authors report it as extraneous, the shroud is also contaminated with DNA from the bird Southern Grey Shrike (Lanius meridionalis), distributed in Southwest Europe, Northern Africa, the Near East, and Southwest Asia. And also with genetic traces of a marine Nemertine worm (Cerebratulus longiceps), from the Northern Pacific Ocean (species description from Alaskan samples, 1901). Once more, as it becomes crucial to remind the readers, because the shroud is 800 years old, bird- or marine worm-DNA must have contaminated the fabric during the past eight centuries.

Fifth, despite these findings, the authors bend over backwards, put aside the age of the shroud and free fall into speculating that if we –somehow– eliminate the noise of the overwhelming DNA contamination, we can “parallel” the genetic patterns of human DNA contamination with the historical path taken by the shroud’s carriers, allegedly from Jerusalem to Turin. A sort of “spatial” retracing of the shroud’s migration. That is, an attempt to find in the genetic markers –which in reality only inform us about the diverse geographic sources of the DNA contaminants– the evidence in support for the historicity hypothesis: Hh that the linen has traveled from Jerusalem to Turin, and via human hand-to-hand (with occasional bird or marine worm intervention) along an envisioned route. And this way of reasoning –by Barcaccia et al.– is so troubling, because it is a blunt Type One Error, a conceptual violation of scientific scrutiny. It picks and chooses what type of contaminant DNA is more informative than other (when all of them are, in principle, contaminants of a cloth one-third the age it is supposed to be), in order to fit the authors’ wish to force support for the historicity hypothesis. And this is done in plain sight of an 800-year young cloth or, in fact, a fake 2000-year-old-wanna-be relic.

“…To be authentic, the Shroud of Turin must be 2000 years old. It is not. Carbon dating places it only eight centuries ago, in Europe. And there is no evidence to link the shroud to Jerusalem, and to the years 30 or 33.”

Sixth, what Barcaccia et al. seem to have found, after cleaning some of the noise in the multiple genetic contaminations (i.e. by discarding some contaminants and keeping “informative” DNA sequences) is an artifact, a byproduct effect of the spatial source of the contamination, that gives the impression of a geographic pattern of migration of the shroud (from Sacred Land to Turin). In reality, it is a pattern of the source of the contamination (not a reflection of the origin of the shroud), consistent with the history of human-worshipers’ approaches to the linen, to touch it. This actually explains the apparent absence of human DNA contaminants from the Americas in contrast to the more-likely-contaminants to be found: the people living nearby the shroud, from the years 1200-1300s onwards. And this is a more parsimonious explanation to the Barcaccia et al.‘s speculations. The authors could have just rationalized over a 2×2 table (see figure below) when designing the tests for: Medieval-origin hypothesis (spatial and temporal evidence) and historicity hypothesis (spatial and temporal evidence). In other words: Medieval-origin hypothesis (Europe and 800 years) and historicity hypothesis (Jerusalem and 2000 years). It becomes obvious that the authors cannot combine, in any manner, one hypothesis with the other because the proposals do not match in time (the time dimension). Therefore, any spatial speculation of consistency, as Barcaccia et al. propose, is senseless. More so when the spatial argument for “possible parallelisms” between hypotheses relies on the capricious use of DNA-contaminants and the exclusion of the timeframe disparity (800 vs. 2000 years). Poor science, indeed.

CONCLUSION: Barcaccia et al. study is another, among many, in-text acknowledgments that the shroud of Turin is a Medieval fake, only 800 years young (C-dating) and not a 2000-year-old relic (as demanded it to be in any test of the historicity hypothesis). Reality occurs in a space-time context, yet the authors chose to put time aside to facilitate survival of the historicity tale. The shroud is heavily contaminated with plant, human, bird and marine worm DNA, a phenomenon enhanced exclusively during the past eight centuries, during which the linen has had increasing exposure to people –and their debris, including critters’ goo– from Europe and nearby locations (not to mention the rest of the world). The genetic spatio-temporal mapping presented by Barcaccia et al. reflects a pattern of contamination by humans of multiple ethnicities, consistent with convergent traveling, from diverse locations, in the direction to the object, the shroud, possibly to worship it. If anything, this paper documents the spatial distribution of human contamination of the linen from likely-geographic locations. It fails to provide any evidence in support of the historicity hypothesis (due to the time dimension incongruity), and it actually strengthens the notion that the shroud of Turin is a Medieval fake. The study by Barcaccia et al. is exemplar of how far poor judgment can go, and how belief in supernatural causation disrupts, distorts, delays or stops (the 3Ds + S cognitive effects of illusory thinking) the acceptance of scientific evidence before the very eyes of the investigators, and with their own data. – GPC

VIDEO: Click on image below to be redirected to NatGeo video Remaking The Shroud, in which techniques for faking it are discussed, and some modern-technology tests shown, including UV light and 3-D imaging.