Over time human cultures tend to naturally migrate, influenced by various push and pull factors. According to the gravity model of migration and specifically the concept of distance decay, very few of these displacements are over long distances. This theory helps explain why we have dominant regional cultures instead of a completely entropic mixture.
Like Athabaskan peoples shown on the map above, some cultural identities have survived treks of thousands of miles. Linguistic evidence shows that the Navajo and Mexica have roots far to to the north of their modern homelands. Certainly they blended with neighboring peoples along the way, but their languages still reflect those particularly far-away kinships. To indulge in a little survivorship bias, not many cultures succeeded at making such epic treks while maintaining their identities.
Critical masses of each group apparently had reason to keep going even while crossing entire climate zones. I'm curious about this behavior, since it's hard for me to imagine that getting away from enemies and finding new sources of food would take quite so much travel.
How could push or pull factors persist across such great distances?