UNIVERSITY PARK, Pa. -- The Maya are famous for their complex, intertwined calendric systems, and now one calendar, the Maya Long Count, is empirically calibrated to the modern European calendar, according to an international team of researchers.
"The Long Count calendar fell into disuse before European contact in the Maya area," said Douglas J. Kennett, professor of environmental archaeology, Penn State. "Methods of tying the Long Count to the modern European calendar used known historical and astronomical events, but when looking at how climate affects the rise and fall of the Maya, I began to question how accurately the two calendars correlated using those methods."
The researchers found that the new measurements mirrored the most popular method in use, the Goodman-Martinez-Thompson (GMT) correlation, initially put forth by Joseph Goodman in 1905 and subsequently modified by others. In the 1950s scientists tested this correlation using early radiocarbon dating, but the large error range left open the validity of GMT.
"With only a few dissenting voices, the GMT correlation is widely accepted and used, but it must remain provisional without some form of independent corroboration," the researchers report in today's (April 11) issue of Scientific Reports.
A combination of high-resolution accelerator mass spectrometry carbon-14 dates and a calibration using tree growth rates showed the GMT correlation is correct.
The Long Count counts days from a mythological starting point. The date is comprised of five components that combine a multiplier times 144,000 days – Bak'tun, 7,200 days – K'atun, 360 days – Tun, 20 days – Winal, and 1 day – K'in separated, in standard notation, by dots.
Archaeologists want to place the Long Count dates into the European calendar so there is an understanding of when things happened in the Maya world relative to historic events elsewhere. Correlation also allows the rich historical record of the Maya to be compared with other sources of environmental, climate and archaeological data calibrated using the European calendar.
The samples came from an elaborately carved wooden lintel or ceiling from a temple in the ancient Maya city of Tikal, Guatemala, that carries a carving and dedication date in the Maya calendar. This same lintel was one of three analyzed in the previous carbon-14 study.