I walked around the main square of San Juan Chamula several times before noticing something odd. The little town is plastered with the signature curlicues of the world's most recognized brand: Coca-Cola. But it wasn't the ads themselves that startled me; you see those in every far-flung, war-torn corner of the globe. Rather, it was the way Coke has been absorbed into a weird social ritual.

Mexico is the world's largest consumer of soft drinks, by a factor of about three to one. (The United States is No. 2.) But here in the southern province of Chiapas, Coca-Cola is more than just a fizzy drink. Around the square in San Juan Chamula, groups of indigenous Indian men, wearing the traditional black wool vests of the Tzotziles, sit around white plastic tables, talking quietly. Each has in front of him a 12-ounce glass bottle of "agua negra," as they often call it, which they drink slowly and earnestly, holding in the other hand the long wooden sticks, known as toletes, that in Chiapas serve as symbols of authority. Nearby, two hefty women sit on the porch of a local store, with colorful shawls and beautifully braided hair. Everything around them, from walls to tables and chairs, is plastered with Coke stickers. Each holds a tiny infant. But instead of a breast or a bottle of milk, they nurse their babies with a cold glass bottle of Coke. Not coincidentally, perhaps, Coke is cheaper than milk.

A friend explains Coke's ubiquity. His grandmother never drank water without putting at least a spoonful of sugar or honey in it to give it some flavor, he tells me. "I'm not a horse," she would say. Luis Lopez Gomez, the 39-year old local distributor of Coca-Cola in San Juan Chamula, is the son of Javer Lopez Perez, who introduced the beverage to Chiapas way back in 1962. Then, villagers walked miles to drink a Coke. Today, Coke has become a wholesale way of life.

If a villager wants something--help repairing his house, say, or a hand bringing in the harvest--he must make his request to the municipal president accompanied by at least one, if not two, cases of Coke. The bottles are then distributed equitably to the other authorities. Such Coke offerings must come in the right packaging. A 12-ounce glass bottle is a sign of respect. Giant 2-liter plastic ones are strictly for family consumption, while cans are for kids. "The authorities here must all have gastrointestinitis," Gomez mutters as we watch people marching in and out of the store bearing crates of the dark liquid.

Sharing a Coke, I soon found out, has, over time, become a way to smooth over social difficulties, bond with friends and reunite former enemies. It might sound strange, but in this part of Mexico where political and agrarian disputes are commonplace, anything that calms tempers is welcome. If someone offers you a Coke, you're obliged to accept--and then return the favor, much the way the rest of the world trades rounds in a local bar.

In San Juan Chamula, some locals believe that Coke is a "hot" drink, meaning it has curative properties. Priests of the local church, which unabashedly couples traditional Mayan beliefs with the Roman Catholic worship of saints, recommend a warm Coke for people who come in complaining of "coldness" or "fatigue." And when it comes time each spring to celebrate Carneval, church groups stock up on hundreds of cases. Poor Pepsi. It sells only about two bottles for every 10 of Coke--and hasn't become a spiritual elixir.