at copan, that king was 18 rabbit. the hieroglyphic staircase was built by his successors in a symbolic attempt to assert the status of copan's ruling dynasty. so in fact, we believe the stairway is a beautiful example of political propaganda. they were trying to make up for the fact that they lost the thirteenth king in war by projecting an image of all of the copan kings as glorious and powerful warriors. keach: and so the elaborate inscriptions of the ancient maya were created largely to bolster the power of their rulers. 3,000 years before the maya, and thousands of miles away in ancient mesopotamia, the sumerians used writing for a very different purpose -- the creation of political, religious and literary texts. and the primary use -- economic record-keeping. i think one reason why sumer had such a different orientation with regard to its writing system is that their economic system was very much more complicated. they had a much more urban-based economy with a lot more craft specialization and a lot more trade.

keach: the copan valley lies 100 kilometers north of ceren. archaeologists began a complete survey of the valley on foot. after 10 years of painstaking work, they have discovered the remains of 4,500 structures. más a usted... cinco centímetros. keach: archaeologist william sanders has been leading excavations in the copan valley since 1980. sanders: we decided to do a series of large-scale excavations out in the countryside to get an idea what the farming population was like. what kind of houses did they live in ? what was their lifestyle like ? probably 80% of the population of copan was in that social category. keach: unlike ceren, the ancient houses of copan had been exposed to centuries of erosion. very few artifacts remained intact or in their original location. still the team finds significant clues. in one structure, the team discovers a razed platform of stone, the remnants of a sleeping bench. in another, they find evidence for a kitchen -- shattered obsidian blades that once were knives and broken pieces of pottery that were once us