Final answer:
A shared theme between the Mayan and Aztec civilizations was their interest in astronomy, which was reflected in their advanced calendar systems and the alignment of their cities. They also had sophisticated societal structures, evidenced by extensive trading networks and significant urban centers.
Step-by-step explanation:
A common theme shared by the Mayan and Aztec civilizations was their interest in astronomy. Both civilizations developed sophisticated systems of writing and had an advanced understanding of astronomy which allowed for the creation of accurate and complex calendar systems. The commitment to astronomical studies is evident in the alignment of cities like Chichen Itza with cardinal directions and in the astronomical data encoded in their written records. Moreover, their knowledge base included a strong grasp of engineering technology, as well as a developed agricultural system, with maize being a staple crop.
The Mayans were not only focused on astronomy, but they also engaged in long-distance trade, another indicator of their advanced societal structures. Their trading networks stretched across Central America and beyond, involving items like salt, gold, turquoise, and obsidian. Through their trade systems and control of trading routes, certain Mayan cities rose to prominence. The Aztecs also built a large urban city, Tenochtitlán, which was a hub of commerce much like the great cities in Europe until its destruction by Cortés.