In this undated photo made available by National Geographic, conservator Angelyn Bass cleans and stabilizes the surface of a wall of a Maya house that dates to the 9th century A.D. in the Maya city ... more 
In this undated photo made available by National Geographic, conservator Angelyn Bass cleans and stabilizes the surface of a wall of a Maya house that dates to the 9th century A.D. in the Maya city Zultun in northeastern Guatemala. Archaeologists have found the small room where royal scribes apparently used walls like a blackboard to keep track of astronomical records and the society's intricate calendar some 1,200 years ago. Anthony Aveni of Colgate University, along with William Saturno of Boston University and others, are reporting the discovery in the Friday, May 11, 2012 issue of the journal Science. (AP Photo/National Geographic, Tyrone Turner) less 
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Associated Press | Photo By National Geographic, Tyrone Turner
Thu, May 10, 2012 3:20 PM EDT