Answer:
Because it's presumed that early people enter through Bering Strait in the North of the continent.
Step-by-step explanation:
According to historians, early people came to America passing through the Bering Strait, but this events are not completely clear. But, this explanation is one reason about why early people took so long to reach South America. Also, that's why they first settled in North and Central America.
So, from this asseverations you can conclude that our Native civilisations have thing in common because they belong to the same people, one example is their believes and religion. Across all America they have some characteristics alike, like the temples build to the gods, and worshiping nature.