OFFICIAL17 What are two disadvantages of radiocarbon dating? [Click on 2 answers.]

[00:00.00]Narrator: Listen to part of a lecture in an art history class.
[00:06.70]Male Professor: Good morning. Ready to continue our review of prehistoric art? [00:13.23]Um, today we’ll be covering the Upper Paleolithic period—um, which I'm roughly defining as the period from 35,000 to 8,000 B.C. [00:25.18]Um, a lot of those cave drawings you’ve all seen come from this period, uh,
[00:30.38]but we'll also be talking about portable works of art—uh, things that could be carried around from place to place. [00:37.96]Here's one example.[00:40.36]This sculpture is called “The Lady with the Hood,” and it was carved from ivory, probably a, a mammoth's tusk. [00:52.17]Its age is a bit of a mystery. [00:55.09]According to one source, it dates from, um, 22,000 B.C., [01:00.21]but other sources claim it’s been dated closer to 30,000 B.C. Um, Amy?
[01:07.75]Female Student: Why don't we know the exact date when this…head was made?
[01:15.05]Male Professor: That’s a fair question. [01:16.68]We’re talking about prehistory here—uh, [01:19.88]so, obviously, the artists didn’t put a, a signature or a date on anything they did. [01:27.20]So, how do we know when this figure was carved?
[01:30.86]Male Student: Last semester, I took an archaeology class, and we spent a lot of time on, uh, studying ways to date things. [01:39.07]One technique I remember was, um, using the location of an object to date it. Like how deep was it buried.[01:45.38]Male Professor: That would be stratigraphy. [01:48.97]Stratigraphy is used for dating portable art. [01:54.91]When archaeologists are digging at a site, they make very careful notes about which stratum—which layer of earth—they find things in. [02:04.32]And, you know, the general rule is that the oldest layers are at the lowest level. [02:10.51]But this only works if the site hasn’t been touched and the layers are intact.
[02:16.53]Um, a problem with this dating method is that an object could have been carried around... used for several generations before it was discarded. [02:26.76]So, it might be much older than the layer, or even the site, where it was found. The, uh, [02:33.23]the stratification technique gives us the minimum age of an object, which isn’t necessarily its, its true age. [02:42.18]Uh, Tom, in your archaeology class, did you talk about radiocarbon dating?
[02:48.65]Male Student: Yeah, we did. [02:52.19]Um, that had to do with, uh, chemical analysis. Something to do with measuring the amount of radiocarbon that’s left in, oh, organic stuff. [03:00.93]Because we know how fast radiocarbon decays, we can figure out the age of the organic material.
[03:08.21]Male Professor: The key word there is “organic.” [03:11.90]Is art made of organic material?[03:15.50]Male Student: Well, you said “The Lady with the Hood” was carved out of ivory—that's organic.[03:20.31]Male Professor: Absolutely. Any other examples?[03:23.42]Female Student: Well, when they did those cave drawings, [03:26.79]didn't they use, like, charcoal? Or maybe colors... dyes made from plants?
[03:32.69]Male Professor: Fortunately they did, a-at least some of the time. [03:35.93]So, it turns out that radiocarbon dating works for a lot of prehistoric art. [03:41.65]Uh, but again, there's a problem. [03:44.37]Um, this technique destroys what it analyzes, so ya-you have to chip off bits of the object for testing.[03:52.26]Obviously, we’re reluctant to do that in some cases. [03:56.85]And, and apart from that, there's, there's another problem: [03:59.42]the, the date tells you the age of the material—say, a bone or, or a tree—the, the object is made from, but, but not the date when the artist actually created it. [04:11.53]So with radiocarbon dating, we get the maximum possible age for the object, but it could be younger. [04:20.68]OK, um, let's say our scientific analysis has produced an age range, [04:27.52]can we narrow it down?
[04:29.38]Female Student: Um, could we look for similar styles or motifs? [04:34.55]You know, try to find things common to one time period.
[04:37.89]Male Professor: We do that all the time, [04:39.93]and when we see similarities in pieces of art, we assume some connection in, in time or place. [04:47.19]But.. .but is it possible that we could be imposing our own values on that analysis?[04:54.30]Male Student: I'm sorry, [04:55.50]I don’t get your point.
[04:57.04]Male Professor: Um, well, we have all kinds of preconceived ideas about how artistic styles developed. [05:03.84]For example, a, a lot of people think the presence of details demonstrates that the work was done by a more sophisticated artist [05:12.24]while, um, a lack of details suggests a, a primitive style. [05:16.89]But trends in art in the last century or so certainly challenge that idea.
[05:22.90]Don't get me wrong, though, um, analyzing the styles of prehistoric artifacts can help dating them, [05:29.04]but we need to be careful with the idea that, um, artistic development occurs in, in a straight line from simple to complex representations.[05:40.14]Female Student: What you’re saying is...I mean, I get the feeling that this is like a legal process, like building a legal case. The more pieces of evidence we have, the closer we get to the truth.
[05:52.26]Male Professor: Great analogy. And now you can see why we don't have an exact date for our sculpture “The Lady with the Hood.”