Archaeologists from Arizona State University have discovered a 1000-year-old burial ground outside the town of Onvas in the northwestern Mexican state of Sonora. It’s the first pre-Hispanic cemetery found in the region. It’s also the first dedicated graveyard discovered in Sonora. Previous burials have been discovered in and around houses rather than in a space set aside for the burial of the dead. The skeletons of 25 people were recovered, eight adults and 17 children between five months and 16 years old. Only one skeleton was female.
Thirteen of them have artificial deformities of the cranium and five of those have dental mutilations as well. This is a particularly significant aspect of the find because intentional cranial deformation and dental mutilations haven’t been seen before in Sonora or in the overlapping cultural areas of the southwestern United States. Before this discovery, the closest these practices ever got to Sonora was Sinaloa, a state on the south border of Sonora, and Nayarit, to the south of Sinaloa.
The kind of cranial deformation found on these remains is fronto-occipital deformation, done by binding flat surfaces (usually cradleboards and other wooden planks) to the skull to apply steady pressure to the frontal and occipital bones of babies, flattening and elongating them. In this case, the lateral bones of the skull were also flattened at angle to give the cranium a “V” shape. In order to take advantage of the unfused and soft skulls of infants, the deformation was usually done to babies starting a few days after birth until they were six months or a year old.
Cranial deformations were done for ritual purposes or to indicate high social rank. Dental mutilations are usually found in adolescents as they were a rite of passage into adulthood. Indeed, the five skeletons with dental mutilations are all over 12 years old. Analysis of the bodies has not returned any obvious causes of death. It’s possible that the high proportion of young people could be the result of poor cranial deformation practices putting too much pressure on the brain and causing premature death.
The burials date to the Late Classic Mesoamerican period (900-1200 A.D.) which was a time of great migrations in the area. It’s also the same period the cranial deformations found in Sinaloa and Nayarit date to, so it seems likely the cultural practices of other Mesoamerican peoples spilled over in Sonora from increased movement and interaction. The Sonorans who buried their dead in the cemetery were not themselves migrating, however. They were settled in place.
Archaeologist Cristina Garcia explained that according to historical sources, the site belonged to the Pima Indians, the region’s cultural group whose descendants moved to what is now the Sonora-Chihuahua state line. It could be part of a settlement located within the transit area where the peoples of the southwest coast of the U.S. engaged in the turquoise trade, “and in this movement of populations, the Pimas adopted new traditions from Mesoamerica.”
A variety of grave goods were discovered buried with the dead. Jewelry and ornaments like bracelet bangles, nose rings, earrings and necklaces were made out of traditional local materials like sea shells from the Sea of Cortes and snail shells. One skeleton was buried with a turtle shell placed over his abdomen.
Garcia notes that this unusual and significant find will spur further excavations in the southeast part of Sonora which has been neglected up until now. The marked differences between the Onvas discoveries and those made in the northeast and west coast suggest there is new archaeological ground to be broken.