The Maya civilization that once dominated parts of southern Mexico and northern Central America was remarkably advanced in mathematics, architecture, and in time- and record-keeping.
Now, an international team of researchers including Anthropology Professor Hector Neff of California State University, Long Beach (CSULB), has generated definitive new evidence about the chronology of events recorded on Maya monuments that are inscribed with dates in the Maya Long Count. The new study shows that the so-called Goodman-Martinez-Thompson (GMT) correlation of the Maya and European calendars is correct.
The study appears in the April 11 edition of Scientific Reports (www.nature.com/srep/2013/130411/srep01597/full/srep01597.html).
Asked about the importance of the study, Neff explained, “It’s important to be able to correlate those Maya dates with our dating system. For instance, we can now reconstruct climate very accurately, and one issue that has been explored recently is the impact of climate fluctuations on Maya society. It appears that the collapse of the Maya probably was occasioned by a series of droughts, and with a definitive correlation, the drought events can be matched precisely to historical events recorded on the monuments.”
Over time, different researchers had developed alternative calendar correlation models based on astronomical observations and other fragmentary evidence from the time of the Spanish conquest. The GMT correlation has been favored by most researchers, especially since radiocarbon dates on a wooden lintel from Tikal, Guatemala, appeared to support it. The lintel, part of a door frame at a Mayan temple, was inscribed with a Long Count date of a battle between two kings. “The idea is that you could date the wood by radiocarbon dating and you could also read the inscribed date that presumably would be close to when the tree was cut, so there should be a fairly close match,” Neff said.
The new study also relied on radiocarbon dating of the Tikal lintel, but took advantage of improvements in dating and other analytical techniques. Lead researcher Douglas J. Kennett of Pennsylvania State University and his collaborators obtained multiple radiocarbon dates from a cross section of the Tikal lintel, which was made of sapodilla wood. Analyses of a modern sapodilla tree showed that calcium uptake fluctuates annually, so calcium could be used to count years on the Tikal lintel cross section.
“You can’t really see tree rings on tropical trees, so unfortunately that’s one problem,” Neff said, but as the annual climate fluctuates, the trees take up varying levels of calcium that can be measured. “If you’re able to analyze the change in calcium along the cross section of one of these lintels, you are able to count the years in between point X and point Y. If you also have radiocarbon dates for point X and point Y, you know how many years elapsed, so using Bayesian statistics, you can tighten up the range of possible radiocarbon dates.
“That’s what’s innovative about this paper. We developed data that showed the number of years in between the dated portions of this lintel, and that constrains the possible dates to a greater degree than would be possible without being able to count the number of years,” he continued.
“That’s where my contribution came in. We used laser ablation inductively coupled plasma mass spectrometry (ICP-MS) to trace how calcium fluctuates across these lintel sections.” The device zaps samples with a laser, forming particles that reveal the sample’s chemical characteristics. “You count the calcium peaks between the radiocarbon dates, so that’s how we counted the years,” Neff said.
“The impact is that now we don’t have to wonder anymore,” about GMT, Neff said. “Almost everyone accepted the GMT correlation anyway, but with the possibility that we were wrong, there was always room for doubt, but now I don’t think there is.”
Neff’s work was undertaken at CSULB’s Institute for Integrated Research in Materials, Environments and Society, a state-of-the art research lab that analyzes material samples for faculty, researchers and business clients. Its advanced equipment and projects have been funded in part by CSULB, the National Science Foundation, the Keck Foundation and others.