by a.d. 600, this was the most complex society in all of mesoamerica. archaeologist william sanders. in this area where i'm standing, which is right on the southern edge of the ancient city, there are between 80 and 100 permanent springs. there is some convincing evidence that at the time of the peak of the ancient city, the water from these springs was harnessed into an elaborate canal system that provided permanent irrigation for at least 7,000 or 8,000 acres of land down on the bottom of the teotihuacan valley, rich, fertile alluvium with very high productivity. this must have provided at least one of the major sources of the production of staple foods for the ancient city at its peak. keach: some archaeologists think the irrigation system was controlled by the state -- the king and his high-ranking elite -- just as the unidad controls it in cuicatlan today. that control gave the elite enormous power, which can be seen in these massive buildings. man: this is the political center of teotihuacan. the temple of quetzalcoatl behind us represents the pow

(narrator) toward the end of the first millennium b.c., a complex society sprang to life in mesoamerica-- imaginative, literate, philosophically-inclined and sophisticated. this eevol ctu ca c out of the primordial forest and sunk its roots into the soil. today, we know the region by its countries-- mexico, honduras, el salvador, belize, and guatemala. but long ago, it was the world of the maya. not an empire, nor a country, the classic maya culture flourished from the third to the ninth century in a far flung collection of city-states. at palenque, tonina, bonampak and other cities, dynastic kings ruled absolutely, controlling trade and tribute. they presided over intricate hierarchies of nobles and officials at courts resplendent with works of art. maya culture, shrouded in a mystery as dense as the forests in which it took root, revealed itself fitfully over three centuries. when the ruins in the jungle were first discovered, there was no way of understanding how the civilization was organized. so it's really through the inscriptions that we've been able to identify kings, to find ou

before the arrival of europeans, two extraordinary civilizations flourished in mesoamerica. both the aztecs and the maya had cultures of startling sophistication, and political systems that were enormously complex. archaeologists are intrigued by ancient political systems. they want to know how these systems were organized and how they evolved. archaeologist arthur demarest. throughout the course of human history, societies have bece ever more complex. political systems have developed -- some successfully, expanding and growing, while othersecline and disintegrate. what are the differences between these societies ? why do some political systems succeed and others fail ? that's one of the central questions that we have to address in archaeology. keach: the aztec political system was one of the great success stories of all pre-industrial societies. they created a rich and powerful empire that dominated millions of people. they lived in the valley of mexico in the area that is now mexico city. before coming to power, the aztecs were just one of a number of small city-states loc

(narrator) toward the end of the first millennium b.c., a complex society sprang to life in mesoamerica-- imaginative, literate, philosophically-inclined th eveolvi ctu and sophisticated. out of the primordial forest and sunk its roots into the soil. today, we know the region by its countries-- mexico, honduras, el salvador, belize, and guatemala. but long ago, it was the world of the maya. not an empire, nor a country, the classic maya culture flourished from the third to the ninth century in a far flung collection of city-states. at palenque, tonina, bonampak and other cities, dynastic kings ruled absolutely, controlling trade and tribute. they presided over intricate hierarchies of nobles and officials at courts resplendent with works of art. maya culture, shrouded in a mystery as dense as the forests in which it took root, revealed itself fitfully over three centuries. when the ruins in the jungle were first discovered, there was no way of understanding how the civilization was organized. so it's really through the inscriptions that we've been able to identify kings, to find out the

in the rain forests of mesoamerica, the ancient maya created magnificent city-states. here three million people once lived. in the earliest cradle of civilization, ancient mesopotamian farmers once made these deserts bloom. halfway around the world, in california, are clues to understanding the fall of mesopotamia, as farmers here struggle to overcome a threat to this fertile garden land. the ruins of ancient societies may hold keys to our own survival as, out of the past, archaeologists explore one of the greatest of mysteries -- the decline and fall of grand civilizations. mission control: ignition... and liftoff. liftoff... keach: for more than five millennia, humankind has seemed to dominate earth, both creating and destroying grand civilizations. each of these human experiments has changed our planet. this high vantage point brings us a new and sobering view. for the first time, we behold our world as finite, limited. on the darkened face of earth, the lights of cities record the expansion of our kind. just 50 years ago, two billion people lived on earth. today ou

in the 18th and 19th centuries, finely carved jades from mesoamerica began to appear in museums and private collections. no one knew what to make of them. some were labeled chinese, others maya or aztec. in 1862, farmer's discovery of a he stone head at tres zapotes triggered speculation that it had be carved by africans who had immigrated the americas. newsreel announcer: pulling it for two hos ov swampland is the last ste of our trip to the spot whe we hope to find the big stone heads of which we ha hrd exciti rumors. obregon: archaeologist matthew stirng setutn 1939 tonravel the mystery o these strange works of art, which by then were being called "olmec." sponsored by the smhsoniainstitut the al raphic s veled thifemari to mexico, launchinthe exvations on the southergulf coast no onenew how old the olmec culture was. many thought it was contemporary or later than tssic maya, w oush from 300 to 9 a.d. newsreel announcer: and here is our objective: tres zapotes, our source of supplies anofabor during theirst t seasons of archalogical work here in the southern part of the state of veracruz

new speaker: we now know athe sitecove m, making it the laest and most complex site in mesoamerica duri the earlyressic orhearlyormative period. obregon: the elite resided on the huge manmade plateau that dominates the site. one house, calle the "red palace," had stone columns and steps and was supplied with war channeled fromeservoirs. ordinary people may have lived in the pm-thatched houses, like some still found ere today. the populationncluded artisans skilled in specializedrafts. cyphers: we have a lot of evidence for workshop activity here. there are areas where theyorked obdian, green stone and even monuments were worked here. the olmecs stored previously made stone monuments and then reworked them or recycled them into another shape with another iconogrhy. we found the tenth and newest colossal head at san lorenzo last year. it wasound in the ravine, a ravine called e ca de la hoche, where three other colossal headhave been found. across the top of the headdress, a three-digited hand or claw descends. this insignia probably has something to do with the name of the person represe