Scientists in Mexico have unearth an ancient cemetery containing remains with cranial deformations so severe that they resemble depictions of alien skulls. Scientists say the deformations were created intentionally to assign social class to the individuals. Per the article:
Cranial deformation in Mesoamerican cultures was used to differentiate one social group from another and for ritual purposes, while the dental mutilation in cultures such as the Nayarit was seen as a rite of passage into adolescence.
I was going to say looks like head binding
I would say it was done with head binding too starting at a very early age.