There are lots of mysteries surrounding Chaco Canyon, a large archaeological site in northwestern New Mexico full of round houses and large stone villages. No one knows why the Canyon, which has little water or arable land, became the center of a regional Pueblo culture that began in the mid 800s A.D. Was it a religious site? A turquoise trading hub? A social experiment?

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Among the biggest questions, however, is why the Pueblo community of Chaco Canyon honored people with six-toed feet. The culture decorated rocks throughout the regions with images of polydactyly and even had those with an extra appendage decorate walls by smooshing their feet into wet clay, reports Aaron Sidder at National Geographic.

Anthropologist Patricia Crown decided to investigate the phenomenon in an article recently published in the journal American Antiquity. Crown’s team first examined 96 skeletons excavated over the years from Pueblo Bonito, a site within Chaco Canyon. Three of the skeletons (an estimated 3.1 percent of the remains examined) had an extra digit next to their little toe on the right foot. That rate is significantly higher than the 0.2 percent polydactyly rate found in Native American populations today.

The six-toed remains were also treated differently, buried in or near ritual rooms. One even had an ornate bracelet on the ankle of the foot with the extra piggy. “We found that people with six toes, especially, were common and seemed to be associated with important ritual structures and high-status objects like turquoise,” Crown tells Sidder. In other words, it seems that extra toes led to extra respect.

In 2012, doctor Maureen Hirthler and hand surgeon Richard Hutchison, wrote a photo essay in the journal Hand describing images of polydactyl hands and feet all over the Four Corners region of the southwest, showing that the Ancestral Puebloans obsession extended beyond Chaco. In their paper, they point out that polydactyl bones have also been found in Sand Canyon, Colorado, and an infant with an extra toe was given a high status burial in Tapia del Cerrito in Arizona.

They also found images of six-digit hands and feet in Sedona, Arizona, Lewis Canyon, Texas and other areas in New Mexico and Utah. While only bones from extra toes have been found, they reason that extra fingers may have been relatively common in the culture as well, though the tiny finger bones are more easily lost or scavenged by rodents.

Eastern New Mexico University biological anthropologist and co-author of the current study Kerriann Marden tells Sidder that there may have been an environmental cause for all the extra toes at Chaco. She speculates that exposure to hazardous materials or some component of their diet while pregnant could have triggered the mutations. In fact, Chaco Canyon and surrounding areas are known for their uranium deposits.