Stone of Kings

by Gerard Helferich

  Who would have collected the stone? Michael Coe suggests that the Olmecs may have mounted armed expeditions to seize their jade, because he can’t believe their rulers would have left the extraction, transportation, and carving of such a valuable commodity to others, any more than a government today would allow counterfeiting of its currency. But Taube points out that no fortresses or administrative centers have been discovered in the region, from which central control over mining would have been coordinated. He thinks it unlikely that the Olmecs and Maya would have traveled to an inhospitable backwater such as the Motagua in search of jade. Instead, he suggests they would have been content to leave the hard, heavy work of collection to locals, stepping in themselves to direct the more lucrative trading and carving of the stone (much as the Antigua jade merchants do now).

  Taube also believes that raw jade was relatively plentiful and hence not terribly costly at the source, that the real value was added only in the skilled labor of transforming it from raw stone into items of ritual meaning and beauty. This is also what happens in Guatemala’s jade industry today. As I saw in my visit to the campo, raw jade commands little in comparison to the prices charged for jade jewelry and carvings. It’s partly this discrepancy between what is paid collectors and what is charged tourists that has led some to disparage the Antigua merchants (though this criticism doesn’t take into account the dealers’ considerable overhead—license fees, salaries, and all those diamond saw blades and drill bits).

  If the archaeological evidence doesn’t prove that Los Jaderos’ or the Ridingers’ sites were worked by the Olmecs or the Maya, how can the issue be resolved? In search of an answer, some researchers have turned to the laboratory and to analytic techniques borrowed from chemistry.

  In the national anthropological museum in Mexico City, there’s a gorgeous spearpoint of glossy black obsidian, nearly a foot long, with edges sharp as glass. And obsidian is glass, formed when a particular type of lava flows from a volcano then cools too quickly to form crystals. This gives obsidian an exceedingly fine texture that allows it to hold an edge sharper than any razor; even today, scalpels made from obsidian are sometimes used for delicate eye surgery. In pre-Columbian times, obsidian tools and weapons were highly sought-after and eagerly exchanged. Hoping to learn about the movements of ancient people, their social organization, and the economic relationships among them, archaeologists were keen to retrace the obsidian trade route. The questions were the same as for jade: Who mined it? Whose hands did it pass through? What was it exchanged for? Where was it worked, and by whom?

  Fortunately for the scientists, every volcanic eruption, even from the same mountain, releases a unique cocktail of chemical elements. And because obsidian is thoroughly mixed in an underground reservoir before being ejected to the surface, it’s remarkably uniform in its constituents. Thanks to both these factors, scientists were able to trace any given piece of obsidian back to the deposit where it originated.

  It was a similar scenario with the clay used to make pottery: The exact mix of chemicals is also unique to a specific location, a fact that archaeologists have exploited to study important issues. Opinion was divided, for example, on the influence that the Olmecs exerted over their neighbors. Did Olmec culture develop first, then spread throughout the region, or were the Olmecs simply one of many cultures developing simultaneously in Mesoamerica?

  Pottery with Olmec-style decoration has been found in a wide swath of Mexico. But was it all made by the Olmecs and traded across vast distances, or did different groups produce their own ceramics, perhaps borrowing Olmec designs? Archaeologists, including Hector Neff from California State University at Long Beach, analyzed the pottery clay using neutron activation analysis, which bombards a specimen with neutrons, then measures the radioactivity emitted to determine its chemical composition. Neff and the others discovered that most of the clay had been dug near the first Olmec capital of San Lorenzo, leading them to infer that the pottery had been made there, then exported to other, presumably less developed cities. Though not all experts are in agreement with this conclusion, the research does show how this powerful technology might be used to shed light on important archaeological questions.

  Could the same impressive results be obtained with jade? In the 1970s, scientists such as Ron Bishop had begun addressing the problem. In the intervening decades, researchers have assembled an imposing armamentarium of techniques, some of which, like neutron activation analysis, can penetrate a piece of jade down to the atom’s nucleus. Whatever technology is used, the fundamental question is: Do pieces of jade fall into a clear geographical pattern (the way obsidian and pottery clay do)? Based on its chemical composition, can we say that it came from here (whether “here” is as wide as the Motagua Valley or as narrow as a specific boulder)? The answer hinges on two factors: First, the composition of jade must vary from place to place. And second, that geographic variation has to be strong enough to stand out above the “noise” of non-geographic differences. Obsidian and clay meet both of these criteria because each deposit is unique, showing strong geographic variation, and each deposit is homogeneous, minimizing the background noise.

  But the geological forces that form jade are more localized and variable, and its deposits are more dispersed and harder to find. So with jade, it’s extremely difficult to assemble a reasonable library of sources. No matter how many samples are collected for analysis, there will always be some that remain undiscovered. This means that when an artifact is tested, its composition often isn’t a close match to any known geological sample. Conversely, if an artifact does resemble a particular source, there’s no proof that it wouldn’t match some other, unknown deposit just as well. And the problem is compounded by a bias in the geological samples that have been tested so far—most have been provided by the Ridingers, whose sources are hardly distributed scientifically throughout the region. No wonder that many archaeologists and geologists who work with jade consider the lack of geological specimens the single greatest obstacle to their research. To Hector Neff, sampling is still so spotty that he isn’t even confident there is any geographical pattern in the chemical composition of jade.

  Then there’s the problem of jade’s heterogeneity, caused when it incorporates trace elements at the time of its creation, resulting in a “nasty” rock that forever bears the accident of its birth. The variable nature of jade’s formation is a boon to the gemologist, because it means that the stone is found in many different colors. But for the scientist, it’s a nightmare, because it means that two pieces can vary significantly in their chemical composition—even if they come from the same outcrop. Faced with this deafening “noise” in their data, it’s impossible for researchers to conclude with certainty where a piece of jade originated.

  To get around the problem, some scientists use statistics to establish the likelihood that two jade samples came from the same place. When you do this, you want to see your data clumped into nice clear groups—and this is exactly what happens with obsidian and pottery clay. But Hector Neff confesses that when he examines plots of jade samples, he has to study them at length before he can organize the data into even tentative clusters. For this reason, he finds it more satisfying to work with other materials that are inherently less messy. Ron Bishop is more blunt. He calls the technique “pseudoprobability analysis” and pronounces the state of the art “God awful.” It’s “horrendously difficult,” he tells me, to pin a specific artifact to a given location within the Motagua.

  Just as it can be hard to find a good selection of geological samples of jade, it can be difficult to get testable jade artifacts. Museum curators are protective of their wares, reluctant to take pieces off display and to let researchers subject them to analysis even with nondestructive techniques. If the method removes even minute quantities of material from the artifact, the museum may well withhold permission, even when the piece is already broken or of only limited archaeological interest.
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br />   Sometimes researchers get lucky, though. When curators at the anthropology museum in Mexico City were restoring Pakal’s mask, which Alberto Ruz had uncovered at Palenque, they found themselves with a few tiny pieces of broken jade left over. They sent them to Hector Neff at Cal State, who subjected them to a method with the inelegant name of laser ablation inductively coupled plasma mass spectrometry, also known as laser ablation ICP-MS, or for our purposes, laser ablation. In this technique, the laser vaporizes a small specimen of the sample, which is then introduced into a hot ionized gas called a plasma, where the extreme conditions strip electrons and create positively charged ions, allowing researchers to make a near-complete inventory of the elements and their proportions in the vaporized sample. In the case of Pakal’s mask, the test showed that its stone was similar to fragments from the Maya workshop at Cancuen. And when Neff was asked to test a carved jade discovered at the Pyramid of the Moon at the great city of Teotihuacan in central Mexico, he was able to determine that it resembled jade from the Motagua Valley. Note that in both cases, though, the jade was judged to be similar, not identical.

  Are there any technological advances in the offing that might allow scientists to match geological samples with archaeological carvings once and for all? Hector Neff points to isotope testing as one method that may hold promise. Whereas techniques such as neutron activation analysis and laser ablation measure trace elements present in tiny quantities in the stone, isotope testing exploits the fact that some elements, such as oxygen and hydrogen, come in different “flavors,” with a variable number of neutrons in their nucleus. These are called stable isotopes, meaning they’re not radioactive and don’t decay or transform into other elements. During chemical reactions and physical changes, the lighter and heavier isotopes separate, leaving a characteristic proportion of each, which can be measured using a mass spectrometer. In the case of minerals, the host environments in which they formed, and even slight changes in environmental conditions such as temperature, leave a permanent, measurable record in the proportion of stable isotopes.

  Do stable isotopes constitute the long-sought “fingerprint” that will positively link pre-Columbian jade artifacts to their geological sources? Researchers have already had success with isotope testing of turquoise and marble. In the case of turquoise, geologist Mostafa Fayek and archaeologist Sharon Hull of the University of Manitoba were able to differentiate thirty-five out of thirty-eight geological samples (and the other three they were able to distinguish with trace element analysis). With marble, other investigators were able to trace the stone in ancient Greek and Roman statues back to the exact quarry where it originated.

  But jade isn’t marble or turquoise. Because jade is harder, it’s more difficult to prepare a sample for testing and more difficult to remove tiny amounts from an artifact without noticeable damage. Before even requesting permission to touch any museum pieces, Fayek and Hull would test their methodology on geological samples, as they did with turquoise, to see whether any meaningful geographical pattern emerged. If they did discern a geographical pattern, they would need to build as comprehensive a catalog of geological samples as possible—a crucial step that has stymied other investigators. Finally, they would need to persuade curators to let them test their artifacts, since a sample ranging from one to five milligrams needs to be removed from the specimen. But before any of this work could even begin, they would need to secure funding. In other words, any isotope testing of jade is still years in the future.

  In the meantime, present techniques remain more helpful in ruling out matches between jade samples than in definitively ruling them in. That’s because, even with current tools, some pieces of jade have such radically different constituents that the specimens seem unlikely to have originated in the same place. The jury is still out on how useful elemental analysis of jade will prove, and in the end the stone may turn out to have no discernible pattern to its geographic distribution. As Hector Neff says, “Sometimes the world just isn’t cut up in the way you hope it is.”

  As for Los Jaderos’ jade, George Harlow confesses to being disappointed with the chemical match between Olmec artifacts in museums and the geological samples brought back from Guatemala. He doesn’t believe that the jade in the carvings came from the site they discovered, and he suspects that either the Olmec mines have not been found, or they were depleted in ancient times and therefore will never be found. In fact, Harlow doubts that Olmec jade will ever be traced to only one location, since like the Maya, the Olmecs most likely gathered their jade from a variety of sources, both north and south of the Motagua. And this idea certainly coincides with the opportunistic ways of prospectors: If jade is to be found in hundreds of places, why collect it in only one?

  Immediately after Los Jaderos’ discovery, Ron Bishop commented, “There is no demonstrated evidence that we have found the source for the Olmec blue jade. I look forward to seeing some scientific data come out, but until then the mystery continues.” A decade later, he hasn’t changed his opinion. “There is no evidence,” he tells me. “It’s still an open question.”

  So have the jade mines of the Olmecs and the Maya been rediscovered, or not? On one hand, it appears that there were no jade mines near the Motagua, in the sense of a few discrete, central sources. But on the other hand, the entire valley and the sierra above it can be seen as one great jade mine, providing the ancients with many different types and colors of the stone, which they extracted from many different places. Knowing the specific outcrop or boulder where a piece of jade originated would doubtless fill in many gaps in our understanding of the pre-Hispanic peoples (as would being able to confirm that a particular piece of carved jade came from a non-Motagua source such as the Caribbean), but at this point, that kind of fine discrimination simply isn’t within the reach of even the most sophisticated scientific analysis. For now, the proposition that the Olmecs once mined the sites discovered by Los Jaderos and the Maya once mined the sites quarried by the Ridingers lies more in the realm of faith than science.

  In piecing together this account, I’ve come to realize that archaeologists, like writers, are in the business of taking the facts as they understand them and trying to weave a convincing storyline. As Hector Neff tells me, “Archaeology is one of the historical sciences, along with geology and evolutionary biology. All have an element of narrative.” Says Karl Taube, “There’s lots of narrative in archaeology, which is one of the exciting things about it; you’re trying to reconstruct the past.”

  It used to be, in the days of, say, Edward H. Thompson and J. Eric Thompson, that archaeologists enjoyed wide artistic license in drafting their stories. And so Edward Thompson could decide that Chichen Itza’s High Priest’s Temple was “not merely the tomb of a great priest, but the tomb of the great priest, the tomb of the great leader, the tomb of the hero god, Kukul Can, he whose symbol was the feathered serpent,” and J. Eric Thompson could insist that the Maya were a peaceful, docile people, a more primitive, uncorrupted version of ourselves.

  But today, archaeology considers itself a science, bound by the methods of scientific inquiry. Instead of the sit-down-and-let-me-tell-you-a-story approach, explains Jeremy Sabloff, now of the Santa Fe Institute, “Archaeology is a hypothesis-driven, dynamic process. It’s true that evidence is open to interpretation, but the question is, can you refine questions and devise research to test hypotheses?” To be scientifically meaningful, archaeologists’ hypotheses about the human past, like geologists’ about the formation of the earth or biologists’ about the evolution of life, need to be what philosophers of science call falsifiable: In order to be provable, they need to be capable of being disproved. With an experimental science such as chemistry, researchers can devise tests to determine whether the real world supports or contradicts their theories. But in the case of a historically oriented science like archaeology, falsifiability can be harder to come by. As David Sedat says, “You can take a very complex set of mater
ials that have been found [such as Olmec-style potsherds] and you can weave three or four different stories about that data, and some of those scenarios will be quite different from others.” The Olmec pottery research is a good example of falsifiability in action: If the clay is from an Olmec city, the hypothesis went, the pottery is Olmec and testifies to a certain influence that the Olmecs exerted over their neighbors; if the clay is from non-Olmec cities, the pottery is not Olmec and doesn’t demonstrate such an influence. Other investigators may disagree with the methods or conclusions, but at least the research is designed to be either supported or contradicted by the data. (In fact, further analysis suggests that the Olmecs may also have imported pottery from their neighbors.) The pottery study is also a good example of how traditional fieldwork, such as excavating potsherds, and newer laboratory techniques, such as neutron activation analysis, can work in tandem. In the words of Ron Bishop, a pioneer in this high-tech/low-tech partnership, “You make up the best possible story you can with the data you have. You want the best fit of all possible kinds of information.” David Sedat is more pointed: “You can make up stories, but you want them grounded in evidence.”

  And yet quantifiable evidence isn’t always forthcoming. Sometimes, “the world isn’t cut up the way you’d like.” And so, being a “nasty” stone, jade yields only so far to chemical analysis, and the data points just don’t fall into neat clusters. We now know that the Maya and Olmecs got most if not all of their jade from the area around the Motagua. But as such large questions are resolved, they splinter into a host of finer, more pointed ones: Did the jade come only from the Motagua? What parts of the Motagua? From both boulders and outcrops? How was it collected? By whom? What was it traded for? How did it find its way into cities? Where was it carved?