Human skulls deliberately warped into strange, alien-like shapes have been unearthed in a 1,000-year-old cemetery in Mexico, researchers say.

Although cranial deformation and dental mutilation were common features among the pre-Hispanic populations of Mesoamerica and western Mexico, scientists had not previously seen either in Sonora or the American Southwest.Cristina García / INAH

Human skulls deliberately warped into strange, alien-like shapes have been unearthed in a 1,000-year-old cemetery in Mexico, researchers say.

The practice of deforming skulls of children as they grew was common in Central America, and these findings suggest the tradition spread farther north than had been thought, scientists added.

The cemetery was discovered by residents of the small Mexican village of Onavas in 1999 as they were building an irrigation canal. It is the first pre-Hispanic cemetery found in the northern Mexican state of Sonora.

The site, referred to as El Cementerio, contained the remains of 25 human burials. Thirteen of them had deformed skulls, which were elongate and pointy at the back, and five had mutilated teeth. [ See Photos of the ‘Alien’ Skulls ]

Dental mutilation involves filing or grinding teeth into odd shapes, while cranial deformation involves distorting the normal growth of a child’s skull by applying force — for example, by using cloths to bind wooden boards against their heads.

“Cranial deformation has been used by different societies in the world as a ritual practice, or for distinction of status within a group or to distinguish between social groups,” said researcher Cristina García Moreno, an archaeologist at Arizona State University. “The reason why these individuals at El Cementerio deformed their skulls is still unknown.”

“The most common comment I’ve read from people that see the pictures of cranial deformation has been that they think that those people were ‘aliens,’” García added. “I could say that some say that as a joke, but the interesting thing is that some do think so. Obviously we are talking about human beings, not of aliens.”