From National Geographic News:
The size of Shakespeare's London, Teotihuacán was built by an unknown people almost 2,000 years ago. The site sits about 25 miles (40 kilometers) north of present-day Mexico City. Temples, palaces, and some of the largest pyramids on Earth line its ancient main street.
Scientists believe Teotihuacán was the hub of trade and commerce in Mesoamerica until the city's civilization collapsed around A.D. 650. When the Aztecs stumbled upon the metropolis centuries later, they dubbed it the "City of the Gods," because they believed it was where the Gods met to create the present universe and sun.
Research has focussed on the Pyramid of the Moon (pictured above):
Excavations also reveal that the pyramid was constructed in seven stages, each stage an enlargement of the last. The work started in A.D. 100 and ended around A.D. 400.
Japanese researchers are searching for the tomb of the ruler who ordered the pyramids construction. It has not found it yet but:
Sugiyama has made some intriguing finds, including dozens of beheaded people with bound hands. The bodies suggest bloody sacrificial rituals ripe with symbolism of military power, he said.
Analyses by Spence of the University of Western Ontario suggest the sacrificed victims came from outside Teotihuacán, possibly as captives brought back from distant territories or battles.
The clues come from oxygen isotopes in bones, which act as geological markers. "They tell you where a person was at a particular time," he said.
Climate and altitude are among factors that affect the isotopes. The isotopes found in remains of pyramid victims differ from those unearthed in city homes.
Researchers also examined the teeth of the victems looking at the growth lines or perikymata:
"Basically growth stops as the body concentrates on survival and repair," he said. "Then as the stress passes, the growth continues again. But there's a line left in the tooth that represents the stress episode."
Because teeth only grow during childhood, scientists can put a general age to when the stress happened. These signatures of bodily stress remain in adult teeth.
"We have shown that in the last century of the city there is a growing problem of some sort. We get more and more indications showing up in adult teeth," he said.
There are two competing hypothesis for the destruction of Teotihuacan. One is that the city was destroyed by invaders from the outside. The other is:
Spence, however, says the evidence suggests to him the fires were set during an internal revolt.
According to his theory, the deteriorating health of the city's poor was likely exacerbated by a drought or a disruption to the food supply. This spurred a revolution against the ruling elite and their symbols of power—temples, pyramids, and palaces.
"The destruction seems to have skipped the vast majority of the city and focused on the elite and punished the elite. That suggests a revolt to me," he said.