Close to four years ago, archaeologist Rodrigo Esparza invited me to visit Presa de la Luz, a dam near the town of Arandas in Los Altos (the Highlands) of Jalisco. Here local rancheros had discovered a great many petroglyphs, some of them large and elaborate, along the shores of the reservoir.
Esparza and other archaeologists determined that the petroglyphs had been made around 1,100 years ago by members of the El Grillo Nation, the people who built the Ixtepete Pyramid, located alongside the Guadalajara Periferico (beltway) at Mariano Otero. The Guadalajara Reporter, by the way, was the first newspaper in Mexico to report the find (January 20, 2012).
While petroglyphs are typically found on vertical surfaces such as cave walls and boulders, most of the engravings at Presa de la Luz are on flat ground where they could easily be trampled on.
Says Esparza: “This project began in 2012 and in our first field-work session we hired 52 people to clean around the perimeter of the lake. This resulted in welcome work for locals and exposed a great many petrograbados we hadn’t seen before. Once the area had been cleaned up, we started registering each petroglyph. That year we found about 105 along the lakeshore. Many of them were pecked crosses.”
The pecked cross, Esparza explained, is an equilateral cross set inside two concentric circles or squares. Its outline is not engraved by chiseling, but made up of small pits which have been pecked into the rock with a pointed tool. “In many cases,” said the archaeologist, “the number of pits adds up to 260, which was the number of days in a Mesoamerican, Prehispanic year.”
Some of the most famous pecked crosses were found at Teotihuacán (the pyramids outside Mexico City) and were thought to have a calendrical purpose. In addition, the four ends of the cross always point north, south, east and west.
“In 2013 we had a second field-work session registering rock art a little further from the dam, in an area covering about 40 hectares,” Esparza continued. “Here we found many more petroglyphs, which brought the total up to 600. During this season, we organized another clean-up and a reforestation project in which more than 5,000 trees of various species were planted.”
My wife Susy and I, along with geologist Chris Lloyd, had been invited along to help hunt for new petroglyphs not yet registered. Guided by the guardian of the petroglyphs, Don José, we drove to an isolated spot on a busy highway and plunged into bushes higher than our heads. Then we came to barbed-wire fences here and there, each requiring us to remove backpacks so we could squeeze through. We ended up in an arroyo filled with huge rocks, but not a petroglyph in sight. So we hiked back to the highway and proceeded to a gently sloping hillside where we found lots more barbed-wire fences, but this time plenty of rock art.
The first one didn’t look at all artistic. It was just a hole about ten centimeters wide and seven deep, nicely rounded. Carving a hole like this, according to archaeologist Joseph Mountjoy, was a simple way of asking the gods for rain and is probably the most common petrograbado of all.
The next most common symbol we saw was the spiral, another prayer for rain. By the end of the day, we had seen a good cross-section of the petroglyphs at Presa de la Luz and I noticed one characteristic many of them had in common: each image has been drawn with a single line. If you challenge someone to draw a mouse or a bird without once lifting their pencil from the paper, they could do it, but this certainly is not the easiest way to draw. The result of such a drawing is something like a maze with one beginning and one end.
Why did these ancient people use this style? Well, it seems to me the “line” is a channel, along which you could move a pebble, as if in a board game. You could even place beetles in the channel, at each extreme and then bet on which will make it all the way to the opposite end. What the engravings mean and how they were used is still a mystery, however.
The rock on which the engravings are sculpted – ignimbrite, according to Lloyd – is also curious.
“This rock is lithic,” he told me. “This means it flowed here from a volcanic source no more than ten or 12 kilometers away.” Finding the source may represent an interesting challenge for geologists.
As “season three” at Presa de la Luz drew to a close, Esparza reflected on the achievements obtained so far. “As of this moment, we have registered exactly 666 petroglyphs, but don’t worry, we’ll get past that number very quickly. What’s exciting is that we’ve already found eleven of the famous pecked crosses ... and recently the archaeological ruins of a pyramid and other ancient monuments near here, which we need to take a look at. I’m afraid it will still be a number of years before we are able to open this amazing archaeological site to the public.”