At 300 m from the Mexican town of Onavas, archaeologists discovered a Hispanic cemetery with 25 human burials.
13 of which have a conehead-shaped skull deformation. But it is unknown why this population specifically deformed their heads.

The bones, which are about 1,000 years old, dating back to 945 A.D. to 1308 A.D., were discovered accidentally during a dig for an irrigation system in the northwest state of Sonora in Mexico. While it’s not unheard of for archaeological sites to be unearthed during modern excavations, the misshapen skulls discovered on the site are fairly uncommon, especially as far north as Sonora.
Although the site, known as El Cementerio, was discovered in 1999, archeologists completed their analysis of the skeletal remains just in January 2013. They plan to continue their research during the next field season.

Discovered on the site were artifacts like pendants, nose rings and jewelry along with the remains of 25 people, 13 of whom had skulls deformed into an alien-looking cone shape. The deformation of human skulls was part of an ancient ritual practiced some 1,000 years ago in that area; it was achieved by binding a person’s head between two blocks of wood to apply pressure on the skull.
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. However, the reason why these individuals at El Cementerio deformed their skulls is still unknown.
Many of the bones were the remains of children, which led Moreno to believe that the practice of deforming skulls may have been inept and dangerous. The practice of artificial skull deformation was not limited to Mexico, though. The Chinookan tribes of the U.S. Northwest and the Choctaw of the U.S. Southeast both practiced the ritual.
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wait a min. — it is just this
Artificial cranial deformation … it is Japanese foot binding. A horrible practice to change growing bones’ shape.
https://en.wikipedia.org/wiki/Artificial_cranial_deformation