Yesterday my wife Diane and I took my 94-year-old mother on a sightseeing trip to see the Casa Grande ruins southeast of Phoenix, “the largest known structure left of the Ancestral People of the Sonoran Desert.”

This four story high structure was built around 1350 AD from bricks made of concrete-like caliche mud, with the floors and roofs supported by beams of pine, fir, and juniper brought from as far away as fifty miles. (The rooflike structure above the ruins was built by the National Park Service in order to protect it from rain.)

Though impressive, I must admit I’ve seen far more impressive American Indian ruins elsewhere. Casa Grande, which means “Great House” in Spanish, suffered as a tourist attraction from two faults:

• Casa Grande was on a flat plain. One could walk around it to observe it, but you didn’t have much else to look at. Many other southwest Indian ruins are built either on cliffs or on top of mesas, giving them a spectacular view of the surrounding country. Such locations enhance the experience for the tourist. Casa Grande did not have this advantage.
• You could not enter the building to see the upper floors or interior architecture. This is undoubtably to protect it, but it left an educated tourist like myself quite frustrated.

Because the site has such a limited tourist value, the Park Service did its usual propaganda dance to try to make the place seem more interesting than it was. As they do at most archeological sites in the southwest, the literature and video presentations emphasized the mysteries of the site. Why was it built? Who built it? Why was it abandoned? As one display plaque noted,

Why did the Hohokam [the name archeologists have given these unknown people] build it? Was it a center of government, religion, trade, education? We may never know.

This same plaque described how some of the windows of the structure align with certain important celestial events, such as the summer solstice and the lunar cycle.

It appears that the Hohokam devised a calendar system based on the motions of the sun and moon, and incorporated that knowledge into their architecture. Like England’s Stonehenge, the Casa Grande may have served as an astronomical observatory and calendar.

Why would the Hohokam fashion such an elaborate calendar? To what use would they have put this information?

I find these kinds of fake questions very patronizing and not very interesting. It is obvious and self-evident throughout the entire southwest (as well as with most ancient cultures) that primitive societies depended on knowing the solar cycle in order to plan the planting seasons. In this case especially, the surrounding archeology within a ten miles of Casa Grande has told us that this was a farming community.

By 300 [AD] the Ancestral People lived in permanent settlements along the Salt and Gila rivers. To irrigate their fields, villages cooperated to build and manage vast systems that diverted water from the rivers. In areas without year-round streams, they tapped groundwater or diverted storm runoff.

Predicting when it was time to plant and harvest their crops was essential. Of course they would have need to understand the celestial calendar. For the Park Service to make believe that this is a big mystery is childish and boring.

Then there is the question of why they built Casa Grande itself. As these primitive people did not have a written language, we can never know the answer to this question with any certainty. However, a review of their history as revealed by archeology — combined with some basic understanding of how most human societies evolve over time — makes the explanation somewhat obvious.

Initially it appears the Hohokam population was relatively small, and they lived in small settlements near their irrigated fields. As time passed however the population grew, forcing them to adjust and adapt.

Around 1150 [AD the Hohokam] left outlying settlements to concentrate in large villages like Casa Grande. Open villages gave way to walled compounds.

At the same time, climate research suggests that the climate in the American southwest was changing, becoming dryer and thus less able to sustain this kind of large population. (The Medieval Warm Period was reaching its peak at about this time.)

In such circumstances, the building of Casa Grande makes perfect sense. The population had grown and had become more urban, a cultural change which usually brings with it a larger administrative class, either governmental or religious. At the same time, the ability to grow reliable crops had declined. Unreliable harvests combined with a larger population meant that knowing the crop cycle was even more critical. Furthermore, having the ability to store emergency food supplies should a crop fail also had increased importance.

Thus, it is quite reasonable to assume that the ruling class decided that it was essential for the Hohokam to build a large storehouse which could also provide the astronomical information necessary to predict the annual growing seasons. Just like today, such leaders would use the crisis to justify the construction of a large public works project, which they also believed with the best of intentions would solve the crisis.

Not surprisingly, Casa Grande was a failure. A large public works project could not solve the problem. Soon after it was built Casa Grande was abandoned and, by the time the Spanish arrived in the 1700s, the Hohokam people had apparently vanished. Today, it is believed that they had scattered throughout the Sonoran Desert, adjusting their agricultural techniques to the dryer circumstances, thus becoming the local American Indian tribes that exist today.

I admit this theory is merely speculative and cannot be proven. But a reasonable theory is far more interesting than a stupid question. Too bad the Park Service doesn’t understand this.

An aside: one reason this theory is not outlined at sites like Casa Grande is because of the obvious political lesson that it teaches. For a government entity like the Park Service to describe a scenario that illustrates the failure of a giant pubic works project is probably asking too much.