From National Geographic News:
Evidence of Maya writing that dates to 2,300 years ago has turned up in a pyramidal structure in Guatemala.
Researchers excavating the site—ruins at San Bartolo in the northeastern part of the country—say the finding could be among the earliest Maya written material ever found.
Currently the oldest known writing system in all of Central and South America dates to about 400 B.C. and is from cultures based in what is now Oaxaca, Mexico.
The researchers did radiocarbon dating on five charcoal samples from deposits found in three layers of the site. Samples from the area where the writing was found dated to approximately 400 to 200 B.C.
Taken together with other radiocarbon dates from the site, the authors have concluded that the text was written between 300 and 200 B.C.—placing writing among the Maya much closer to the earliest known writing systems from other Mesoamerican cultures.