Southern Mexican Indians are either Mayan, Aztec or from an ancient indian tribe called "Mexica".

The brown Mexicans you see here are mostly Aztec and Mayan.

Mestizos are indian and white mix [bi-racial]the further north you get, the more caucasian they are [up to 90% white].

But the Indian groups are all related from Alaska all the way down to the tip of Argentina.

Probably originating in China/mongolia.