Coneheads
Cultures on every continent have practiced skull binding since people became people. Neathertals did it, prehistoric Homo Sapiens did it, Incans, Egyptians, Celts, Sumerians, Indians, Chinese and of course the ancient Mayans were no exception. Using various devices, baby’s heads were bound from birth to produce a long oval shaped head. This deformation extends the total brain volume by up to fifty percent at the expense of compressing the pre-frontal lobes. No one in modern times knows what the mental effects of this practice might be or why it was so common in so many places for so long. In the absence of a perfectly oblong head, headdresses were used to mimic the desired shape. This global practice really only died out about two hundred years ago.
In addition to loving coneheads, the Mayans also prized, crossed eyes, and droopy lower lips. All of the Mayan rulers are depicted with these features. Interbreeding of ruling families may have lead to genetic conditions with these attributes, leading to their perceived status. In any case, if they weren’t fortunate enough to actually give birth to a coveted downs syndrome baby, you could bind their skulls, mutilate their lips and even train crossed eyes by mounting some dangling beads close to your child’s eyes to focus them inward.