They were unearthed in the northwestern Mexican state of Sonora at a site known as "El Cementerio" when workers stumbled upon the remains accidentally while digging to install an irrigation system. According to Time, the bones date to between A.D. 940 and 1308, making them around 1,000 years old.
The skulls appear to have been intentionally deformed until they resembled something akin to the "Coneheads," the fictional alien family made famous on "Saturday Night Live" in the late 1970s.
“This was an Hispanic cemetery with 25 skulls, and 13 of them have deformed heads,” Cristina Garcia Moreno, a researcher from Arizona State University who worked on the project, told ABC News. “We don’t know why this population specifically deformed their heads.”
Although skull deformation was a documented ritual among many indigenous groups in southern Central and South America, LiveScience reports this is the first discovery of the practice so far north. "The most important implication would be to extend the northern boundary of the Mesoamerican influence," Moreno explained to LiveScience.
In an earlier interview with HuffPost Weird, Ryan Matthew, a host on the Science Channel, explained that the process of cranial deformation usually began in childhood.
"When you were a newborn baby, you would be cradle-boarded," Matthew said. "They would put two boards around the head and wrap it very securely. Because the head of a child is very soft, it can be manipulated forward, but the process would take several months."