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 our global population has reached five billion. Within the next generation, it will double once more. Our exponential growth now threatens the very resources that sustain life. The abandoned ruins of ancient societies hold clues to our survival. But to learn from our past, we must discard a romantic image of these earlier and more simple societies. Archaeologist william sanders. A commonly held notion among the public at large and also among some of my anthropological colleagues is that nonwestern peoples live in harmony with nature, that they have relatively stable environmental relationships. What archaeology teaches us is that thats not true. Keach in the new world, human beings appeared for the first time more than 10,000 years before the birth of christ. Over the millennia, grand citystates emerged in the tropics of mexico, guatemala and honduras. This is the realm of the ancient maya. They built magnificent cities and peopled them with the portraits of their kings. These are the ruins of copan in honduras. The mystery of the rise and fall of these maya kingdoms has fascinated archaeologists for centuries. It is a puzzle presented in 1839 by the words and etchings of explorers Frederick Catherwood and john stephens. Architecture, sculpture and painting, all the arts which embellish life had flourished in this overgrown forest. The city was desolate. It lay before us like a shattered bark in the midst of an ocean, her masts gone, her crew perished, and none to tell whence she came, to whom she belonged, how long on her voyage, or what caused her destruction. Now, 150 years later, the puzzle first put forth by stephens and catherwood is being pieced together. Archaeologists are rebuilding the ancient city of copan a thirtyacre maze of ball courts and plazas, monumental sculpture and colossal stairways. Intricate and beautiful maya glyphs have been deciphered to reveal the history of a grand dynasty that once ruled here. High atop pyramids, the kings of copan conducted rituals to invoke the protection of their royal ancestors. On altars, they sacrificed sacred animals, like these jaguars, to appease a world of spirits. One such altar has been discovered at copan. Altar q is inscribed with portraits of kings, the royal lineage of the 16th ruler of copan. Archaeologist bill fash. Now the reason behind altar q is to show that the 16th and final ruler of the site derives his right to rule from the fact that hes a descendant of each and every one of these illustrious royal ancestors. He makes this point very clearly by showing the founder in the act of passing the baton of office to him as king. Keach the copan dynasty endured for almost 400 years, recording their triumphs on elaborately carved altars and stelae. Carved here, too, is a record of their downfall. This is altar l. Its the last carved monument at the site, and, in fact, represents a metaphor for the political collapse of this city. On it we see an attempt on the part of the 17th wouldbe ruler to copy the great dynastic altar, altar q, of the 16th ruler. But in order to get to the throne part, you have to go to the back side of the altar. In so doing, what you discover is that the top and these two sides of altar l were never even carved. And, in fact, on the back side where youd expect to find the rest of the text saying seated as king, you just have a blank panel. They never finished carving the text. So on that date on the 10th of february in a. D. 822, when the sculptor dropped his tools and walked away, that was effectively the end of the copan dynasty. Keach the fall of the maya dynasties was not only dramatic but widespread. Within 150 years, many of the grandest maya palaces lay abandoned. At palenque, copan, tikal across a landscape the size of england, all was in ruin. Archaeologist william sanders. All over the lowlands about 800 a. D. , in hundreds of maya sites, they stopped erecting dated monuments, and they stopped building palaces and temples. This was an extraordinary historical event. A population of three Million People or more drops down to a few tens of thousands. And it looked as though this happened over a period of only a century or a century and a half, according to the accepted chronology. Keach the apparent swiftness of the collapse suggests a disaster a plague, drought or warfare. Could the maya have been destroyed by foreign invaders . Here in mexico city is a vivid example of what often happens when one society conquers another. The Mexican National palace stands in the center of the city. In its courtyard, the murals of diego rivera depict the spanish conquest of the aztecs. With guns and cannon, horses and armor, the conquistadores of Hernan Cortez attacked the armies of the aztec emperor, moctezuma. For a time, the aztec orders of the eagle and the jaguar repelled the assault. But the aztecs traditional indian adversaries joined forces with the spaniards. The alliance destroyed the aztec empire. The spanish built mexico city atop the ruins of the aztec capital. In 1978, excavations for electric lines first uncovered aztec sculptures, including this huge carving of the moon goddess. Today archaeologists have revealed the capital of the ancient aztec empire beneath spanish streets. They have reconstructed a great temple that was rebuilt and enlarged many times by the ancient aztecs. The ruins of the temple lie beneath the main spanish plaza, called the zocalo. Archaeologist william sanders. Sanders i think the zocalo of mexico city is the most exciting place on earth. In front of me you can see the material remains of three successive civilizations the great temple of the aztecs, the cathedral, a symbol of catholic spain, and, in the distance, the torre latino, which is a symbol of modern industrial mexico. Prior to the aztecs, we have evidence of two earlier civilizations in the same valley. So we have successive civilizations, one replacing the other, for 2,000 years. And this is the normal pattern that archaeologists and historians find when they study a region of the world. What changes are the elite levels of culture the Political Institutions of power and the religious ideology that validates that power. But there is also a continuity. The fact that we have a city here through three successive civilizations is an example of that. And that continuity exists because the changes only occur at the top. The bottom level, the working class, persists and provides the labor and the goods to support the system. Keach with stones from their own temples, aztec laborers were forced to build the spanish cathedral. A new religion replaced the old. But the cathedral is also a symbol of continuity in mexico. Many who kneel to pray here are direct descendants of the aztecs. For the commoners, the spanish conquest and the later mexican revolution brought merely an end to one form of government and the imposition of another. Its a pattern repeated around the world. This is the ancient roman forum. In the 4th century a. D. , the empire finally crumbled. Yet today, as in mexico city, life continues amidst the ruins of romes former glory. The collapse of maya civilization was quite different. Warfare and conquest cannot explain the total abandonment of these once grand cities. Even if warfare had taken many lives, the maya population should have revived within a few generations. What could have caused such a widespread disaster . 2,000 miles from the maya heartland, a similar puzzle intrigues archaeologists in the american southwest. Nestled into the cliffs at mesa verde in colorado are the abandoned ruins of the anasazi, the ancient ones. At chaco canyon, in new mexico, the anasazi built great residential and ceremonial centers. Sometime between the 11th and 13th centuries a. D. , all of these communities were abandoned. In the southwestern corner of colorado, one group of anasazi flourished at a place called sand canyon. Now overgrown with juniper and pinyon, sand canyon pueblo was once a thriving, densely populated town. Here, a team of archaeologists is excavating an abandoned anasazi settlement. Woman the bubble in the center. About 500 people once lived here in more than 400 rooms. The rooms are grouped around circular chambers, called kivas, where the anasazi practiced rituals. The rituals were secret, so the kivas were built below ground level and concealed beneath an earthen roof. Heavy beams, like this one, supported the roof. Curiously, many beams are charred. The kivas had been burned. Archaeologist william lipe. Im not sure what it means, but i can speculate that the burning of the kiva roofs was some type of closing down ritual for this village. Weve seen that a few other places in the northern southwest at a time when there was a substantial movement of population out of an area. So i think thats a possibility that they burned, intentionally burned, the kivas when they left this area for good. Keach to find out when the site was abandoned, a charred roof beam is wrapped and sent to a laboratory. The anasazi often moved their villages, but usually only for a short distance. Lipe ordinarily when the anasazi left a settlement, they took most of their material equipment with them. If they werent going very far, they might even take the roof beams. Sand canyon pueblo is really different. This is a little rectangular ceramic box found in the niche in the kiva, probably left right where it was ordinarily left when they abandoned that part of the site. Valuable Little Things like this ordinarily wouldnt be left by people. Keach so the archaeological evidence suggests that the people of sand canyon deserted their pueblo to migrate a great distance. What could explain this abandonment . Clues can be found in the traditions still nourished by a few anasazi descendants. Rena swentzell is a pueblo indian from the tewa community in new mexico. [ woman speaking native language ] interpreter in our pueblo, we still dance the corn dance. We dance to tell the corn mothers how we appreciate their gifts. We want to thank them for a good life, for giving us the breath of life. Keach until a. D. 500, the indians of this area were nomadic hunters and gatherers of plants. At that time, they began to cultivate corn and live in settled communities. They were dry farmers, dependent on spring rains to germinate seeds and summer downpours to nourish growth. Anasazi ritual reflected the importance of corn for survival. And in these arid soils, the growth of corn depended on rain. This sample of wood contains a record of ancient rainfall patterns. The patterns are decoded by archaeologist jeffrey dean, director of the Tree Ring Laboratory at the university of arizona. Thousands of samples of trees have been collected here, an amazing record of rainfall that extends back to the time of christ. The vertical bands in each sample are growth rings. Tree growth is largely determined by moisture. Thick rings are created during years of high rainfall, thin rings during dry years. By carefully measuring the thickness of the rings, dean recreates the pattern of rainfall when the tree lived. By sampling thousands of trees from across the southwest, he maps the ancient climate. Tree rings from the sand canyon area disclose that from about 1270 to 1274, people experienced normal or above normal rainfall patterns, shown here in green. But low rainfall, shown in red, began in 1275 and lasted for 14 difficult years. Lipe so i think what happened was that people got in trouble here in the late 1200s with a severe drought. Some people tried to stick it out, didnt make it, perhaps suffered famines or other calamities. But probably the majority of the people bailed out and joined related pueblo peoples to the south. This was also a period of extremely high population density in that area lots of people per square mile. And it came at the end of a long period of farming in that area that depleted the agricultural resource. Those three things put together created a situation that perhaps was almost unique in the history of that southwestern corner of colorado. Keach the collapse of anasazi society was triggered by drought, an act of nature beyond their control. Population growth and depletion of this fragile arid environment may also have been factors. We often think of people like the anasazi as living in harmony with nature. Just how common is it that ancient societies overexploit their environment and threaten their own survival . At the State University of new york at stoney brook, a team of archaeologists seeks answers. Elizabeth stone and Paul Zimansky study the plans of an ancient neareastern city they recently excavated. Woman so this must be the back wall of the palace. That you can pick up on the photograph there. Keach the city is called mashkan shapir. It was one of scores of ancient cities that thrived 4,000 years ago in the deserts of what is now iraq. This is the realm of ancient mesopotamia. Centered around grand palaces and temples, urban life emerged in an area that archaeologists call the first cradle of civilization. Today the ruins of these once grand cities crumble in the dry desert earth. But how could civilization have emerged in such an arid environment in the first place . And what might have caused its destruction . Data from mashkan shapir provide clues. Stone we found a very large palace structure, which was decorated with baked clay pieces, showing the citys own god nergal, the god of death. Zimansky there was a large temple area, in which we found pieces of sculpture lifesize and somewhat smaller of animals, human beings, all of which were probably part of the temple furniture. Keach they also found fish hooks, weights to hold down nets and fish spears all evidence there was once water here. Written tablets like these describe mashkan shapir as a major port. But the city was 20 miles from the tigris river and 30 miles from the euphrates. How could a major inland port or any city, for that matter, survive in the desert so far from water . Stone begins a search for the source of water. For a perspective not possible from the ground, she orders a digital photograph of the area from the french spot satellite. With artificial color, she analyzes the image on the stony brook computers. Stone in this blowup, you can see the perimeter of the site right here, the two harbors one here and one less clear over here, which were fed by two main canals, one here and one here. The whole picture is one of a great deal of water at the site. In this view, you see one large channel here, which must have fed the site, which is located here. Tracing the channel upstream, we suddenly found that it had two sources one coming here and the other here. The presence of the two channels explains not only how mashkan shapir could have had boat trade with both the tigris and the euphrates systems, but also the large amount of water that was available there. Keach the water flowed through a network of canals, allowing irrigation the lifeblood of civilization in this desert. Archaeological study of the canals presented an intriguing puzzle. Within several decades of their construction, many of the canals were abandoned and new ones built to take their place. Why would the mesopotamians abandon these waterways after investing so much labor in them . Halfway around the world, in the Central Valley of california, is an important clue. As in ancient mesopotamia, the government here constructed an elaborate system of aqueducts and canals. Water from the nearby mountains has turned the fertile, but arid San Joaquin Valley into one of the most productive agricultural regions on earth. Man at the turn of the century, this was largely a desert jack rabbits and rattlesnakes, a few pioneering souls that began small farming operations out here. Keach for Larry Turnquist and thousands of other farmers here, the desert began to bloom when large amounts of water were made available for irrigation. For all of its bounty, however, irrigation carries the seeds of its own destruction. Turnquist this area, the San Joaquin Valley, has the ability to continue to be the bread basket for the world for many, many years to come. But in order to continue this abundant production here, we have to solve one enormous problem. Salt. Keach salts like sodium chloride and Calcium Carbonate are turning some of the worlds most productive farms into saline wastelands. In many of the worlds arid regions, salt is a natural component of soil and water. When Irrigation Water evaporates, salts are left behind, contaminating the soil. To prevent this, additional water must be applied to wash the salts down and away from the root zone. The great quantity of water cleanses the soil. But in the process, it, too, becomes saline. Deep beneath these fields, layers of rock or clay form a barrier. With nowhere to go, the saltwater rises towards the roots, inhibiting growth or killing the crop. In wells throughout the valley, technicians easily measure the short distance to the saline water table, and test for the salt content. The saltwater has risen almost to the surface beneath nearly a million acres. Experiments like this canal to take the saline water to the sea have largely failed. Turnquist as we irrigate, we continually add a little salt to the soil. And i look at some of my neighbors lands, and i can see the saltwater right at the surface. And i look at one parcel of my ranch, and the salts getting closer and closer. And as the salt gets closer and closer, i see losing my ranch. Keach by the 18th century b. C. , civilization had largely abandoned southern mesopotamia. Evidence of salt damage here can be found in ancient texts. Clay tablets like these describe a host of changes in the harvest due to salt in the fields. Archaeologists continue to debate the causes of this collapse, but one fact is clear irrigation and salinization contributed to the decline of city after city. In this cradle of civilization, humans demonstrated they could destroy their environment as quickly as they could master it. But there are no deserts in mesoamerica. What c