How are the different "tribes" (for want of a better word) - Olmec, Toltec, Maya, Inca, etc. - related?

Nahuatl dialects Totally Explained

Mirellle ashed the question used as a title.

The question is not quickly answered in detail. My reading from several books on my shelves has produced the following summary. Some of this is simply my assumption in order to produce a simplified answer.

All ethnic groups are descended from the same original peoples who crossed from Siberia to Alaska during low periods of ice as geology changed. There were probably some migrants across the Pacific who brought some cultural influence. Two major populations arrived into central Mexico; one via central valley (deserts ) from SW side, another through Mississippi river to Gulf coast. The desert people remained uncivilized as the gulf people became the first civilization, Olmec, along the coast now called Veracruz. The populations merged and moved through much of the region forming Maya and Chichimeca ( uncivilized nomads ) groups. Traders moved continuously between the groups and culture diffused. Teotihuacan and then Toltec and then Aztec emerged in central valley, with trade continuing.

The 260 day ritual calendar was in cultural records of all groups. It was extended to agree with an agricultural calendar of 365 days by slightly different methods in central valley cultures and southern, Maya, groups.

I have been concentrating on a study of the calendar that survived in Codex Borgia. There are other studies of extensions fro other sources but all known calendars include the ritual calendar of 260 days. I have not yet discovered any original manuscripts which can be read from the original writers in the Maya group of cultures.

There was an elaborate priesthood who learned to predict lunar and solar eclipses as well as changes in position of Venus. In my opinino, they used their scientific knowledge to mislead the gullible through astrological fortune telling.

This is a brief answer. You are welcome to join the search for original documentation and direct interpretation of the mysteries that were not recorded. Those were a people with advanced intelligence and most of their documentation was destroyed.