If you are going to visit the local villages of San Juan Chamula and Zinacantan it's best to hire the services of a local guide. This is because these communities are distinct: they have customs and practices which will make little sense to an outsider without the explanations of someone with local knowledge of society and culture in the villages.
75% of Chiapas' population is made up of indigenous peoples. Chiapas' indigenous people live within 9 distinct communities, each with its own language, traditions, costumes, belief systems, patron saint, spiritual leaders and healers, and rituals that create a complete and distinct culture. Each community has its own identity which is most visible by the colours and design of the clothes they wear. You can always tell which community a person is from (whether they are a baby or an old man or woman) by the clothes they wear.
People from different communities do not marry neither must detach themselves from the religious protocols set out by the community. To do so causes expulsion from it, leaving the couple (and their offspring) to fend for themselves outside of the protection and structure of the communities they were born into.
Religion here is a mixture of Catholicism and Maya Ritual. Chamulas revere St John the Baptist above Jesus Christ; St John's image is more prevalent inside the church. The Temple of San Juan (St John) is covered in pine needles: the pine tree is an important part of Chamula culture: their towns and villages are surrounded by pine trees.
Symbolism is strong: coca-cola is used in rituals, an apparent substitute to Atole (corn based drink) made from black maize; eggs are used to absorb evil; agua ardiente (cane based alcohol) is used as a substitute for wine; religion, politics and rituals are deeply intertwined.
The Tzotzil culture is submissive by western standards: women always follow behind the men; men chop the firewood, but women carry it; you will never see a woman wearing a hat. As you drive or wander through this region, expect to see a world far removed from anything you expect in a developed country. You will see men and women working the fields using rudimentary tools and elbow grease.