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Digging into the reportage: Archaeology and the media

June 15, 2012

The press loves archaeology stories. Newspaper, online, TV, radio, it doesn’t matter. You can find some report about a new excavation, a new finding, a new interpretation, practically every day. I flatter myself in thinking that’s because the subject is inherently interesting to lots of different people, and that’s probably true to some degree. It’s also true that archaeology stories are fairly easy to report—we’ll often hold news conferences or release statements to media on the work we’re doing, and many of us welcome journalists to visit our excavations. A lot of archaeologists, myself included, consider this part of the public outreach that we’re committed to doing.

So I think in general, media reports on archaeology topics are good things. But it’s not enough to simply read them, you have to be a critical reader. You have to approach a newspaper article or a documentary with an eye toward what is being claimed, what evidence is being presented, and most importantly, the space between those two things.

Below the break, I’ll offer two examples of recent stories on archaeological topics: the possibility that Neandertals made at least some cave paintings in prehistoric Europe; and a claim that bones from the biblical John the Baptist have been found in Bulgaria. I’ll go through the reported evidence for the claim, and talk a bit about what I mean by looking critically at the evidence and conclusions, and the space between them.

Hand stencils at El Castillo Cave, Spain, dated to more than 37,500 years ago. Source: New York Times/AFP/Getty.

Our first story was widely reported on June 14, by, for instance, the wire service AFP, Discovery News, and The New York Times. It deals with a new study that offers tantalizingly old dates for 50 cave paintings at 11 caves in northwestern Spain. At issue is the result from three of those dates that point to a minimum of 40,000 years old. That’s important, because about 40,000 years ago (give or take, and dates are constantly shifting) is where  current thinking places the final eclipse of Neandertals in Europe, either through extinction, or through interbreeding with anatomically modern humans, or a combination of the two. Put another way—the way much of the reporting presented it—that means it’s possible that Neandertals made at least some of the paintings.

The second story seems to have gotten less attention, judging by the fewer hits on a Google search. You can find reports from The Telegraph, The Daily Mail, and, again, the AFP wire service. This one makes the claim that new radiocarbon dates support the possibility that human bones found in a monastery on the Black Sea are those of John the Baptist—the one from the Bible. Local tradition says the Bulgarian monastery—translated as “Saint John”—houses relics of the biblical figure. Radiocarbon dating of one of the human bones returned a date, as one of the researchers involved says, “clearly consistent with someone who lived in the first century AD.” And a related DNA study showed the four human bones were from the same person, probably a man, with Middle Eastern ancestry. The conclusion is that the findings—and note the careful language here—do not rule out the possibility that the local John the Baptist tradition is true.

A quick caveat on the second story: What I’ll be discussing here is strictly about how well the evidence presented in the report makes the case for the conclusions presented. I have nothing to say about the reality of events presented in religious texts, or about anyone’s deeply held faith. Regarding the latter, I might gently ask why faith requires evidence, and leave it at that. Onward.

How old, and how do we know?

Both stories hinge on dating methods, so let’s take a look at how each one discusses the ways the archaeologists arrived at the dates in question.

Nearly all of the Neandertal articles I read did a good job of discussing the pretty spiffy means of dating the cave paintings. The researchers used a method that is similar to radiocarbon dating—you’ll often see it called “carbon 14 dating”—that depends on measuring the radioactive decay of isotopes of certain chemical elements. In radiocarbon dating, a sample of something from an archaeological site that contains carbon—charcoal, bone, etc—is analyzed for the proportion of the radioactive carbon isotope C14 to its stable carbon cousins. From that proportion, we can tell how many half-lives of C14 have elapsed since the organic material stopped taking up C14 from its environment—the wood was chopped for burning, the person whose bone we’re examining died, and so on. That number is then translated into years, and you have a “radiocarbon date.”

This is obviously quite simplified, but there’s three points to make about it. First, radiocarbon dating is a long-established and reliable method of dating, and because it depends on measurable and known physical properties, multiple tests should give the same (or very similar) results. Second, C14 dating has a couple of serious  limitations. Only things containing carbon can be dated by it, and there’s a point that things are too old for it to be a useful and reliable method. Unfortunately, once we start talking about 35-40,000 years back, we’re approaching/passing that limit, and radiocarbon dating becomes less precise. But third, the concept of radioactive dating isn’t restricted to carbon isotopes. You can use other elements, by basically the same process. Other elements don’t necessarily have the same restrictions that carbon does. And that’s what happened with the Neandertal study.

Instead of carbon, the researchers used a uranium isotope they collected from, not the pigments used in the paint (that would damage them), but the natural secretions of calcite that covered the pigments over time in the limestone caves. In other words, what was being dated was not the paintings themselves, but the stuff directly covering them. Imagine a bare plaster wall that you cover with green paint, and after it dries, you cover the green paint with a coat of red paint. The red paint layer is the “youngest” thing on the wall, the green paint layer is a bit “older” than the red, and the plaster wall itself is the “oldest.” Same idea here: the cave art itself is actually older than the dates the archaeologists reported, because each painting had to have been placed on the cave wall before the calcite—the stuff that was actually dated—covered it over.

Bartoleo Veneto’s “John the Baptist,” 16th Century. Source: Wikipedia

In the case of the Bulgarian bones, the stories report that radiocarbon dates point to the early first century “AD”—I find that a bit odd, as the generally accepted terminology is “CE,” which refers to the “common era” and is simply a way to talk about time that’s understandable to people who don’t necessarily reckon it from the birth of Christ. What we’re not given (in either story) is the range of dates that all forms of radioactive dating necessarily return upon analysis. Radioactive decay is actually measured many, many times in each sample, so there’s a bit of natural variation in a “single” C14 date. You might get a plus-minus range on one C14 date of 40 years, or 60 years, or 120 years. Think of it like the margin of error you see in polls and surveys.

In many cases, like with the cave paintings, a few hundred years doesn’t make much difference, as our chronology for Neandertal occupation of Europe is not that fine-grained. But in the case of the relics, decades matter. If we can’t positively date the bones to a pretty short time span in the first century, the whole claim collapses.

Weighing the evidence and conclusions

Both stories hinge on the strength of dated evidence to support their claims. I’ve discussed the dating a bit, and argued that in both cases, the dating method is solid and reliable, and each method used is appropriate for what the archaeologists were trying to accomplish. Because the date and margin of error in the relic story are not reported, we can’t really judge for ourselves.

But I’ve said almost nothing about the actual conclusions reported in the stories. It’s quite interesting that both of them are, to my mind, appropriately cautious. There’s lots of “maybes,” “possiblys,”and “perhapses.” That can be maddening to read, but it’s how archaeologists generally talk. We’re reluctant to deal in absolutes, particularly when the picture is always changing due to new evidence, like in Neandertal-era Europe.

In the case of the cave art story, I’d say the evidence is actually a bit stronger for the “perhaps it was Neandertals after all” camp, simply because the pigments must be considerably older than the dates returned by the study. I’m quite impressed by the use of uranium-series dating on the calcite patina. That seems both robust and elegant. Of course, I’m not as familiar with that particular method, and I’ll bow to those with better knowledge if there’s some glaring problem that I’m not aware of.

The point, after all the talk, is simply this: Read media reports of archaeological findings with a critical eye. Try to distinguish what the archaeologist is claiming from what the reporter is claiming, and weigh how well the data support the claims. “New discoveries” make headlines, along with “the oldest” this and “the only” that. For me, though, the really interesting part of the field isn’t all the things, but how all the things make us think.

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