One reason for low doorways in some cultures has been to make it hard for invaders to run in. It is a lot easier to clobber someone on the head if they have to bend over to walk in. Blam mentions that blood studies have been done. Does this include modern DNA comparisons between modern Zunis and modern Japanese or Ainu? It is well known that the Aztec language (Nahuatl) belongs to the family of Uto-Aztecan languages. The Utes are in the US. In some histories the Aztec are said to have originated from the savage freedom loving Chichimec tribes from northern Mexico. It is certainly possible that these were tribal groups driven out by the “civilized” tribes with their “urban” culture, that drifted down into northern Mexico, and some of whom eventually made it all the way to Mexico City where they developed their own warfaring civilization.
https://en.wikipedia.org/wiki/Chichimeca
Apparently nothing unexpected...so far.
Ancestral Puebloan mtDNA in Context of the Greater Southwest
"The Tommy and Mine Canyon sites fall on opposite sides of the F1 coordinate, reflecting their different frequencies of haplogroups A and B. The Tommy Site forms a cluster with the Jemez, Fremont, and Zuni, and Carlyle's Anasazi data, reflecting these populations' high frequency of haplogroup B, typical of Southwestern populations. "