Enlarge Image © Luca Tettoni/Robert Harding World Imagery/Corbis

Humanity and coffee go back a long way. We're very well acquainted. One might even call it a love affair, if one had particular affection for the caffeinated brew.

It's widely believed that the relationship began in Ethiopia, to which the arabica coffee plant is native. From there, it spread to the Arabian peninsula, exported from Ethiopia to Yemen, where it's generally accepted that coffee was first known and consumed in the 15th century.

According to a study conducted by researchers at the University of New Mexico, however, the people of the Southwestern United States and Northwestern Mexico were way ahead of the curve, drinking caffeinated drinks as early as 750 AD, over 1,200 years ago.

"I think the primary significance is that it shows that there was movement of two plants that have caffeine in North America -- that they were either exchanged or acquired and consumed widely in the Southwest," said lead author Patricia Crown, University of New Mexico Distinguished Professor of Anthropology, on the study's findings.

This conclusion was drawn after the team studied organic residue left on sherds of cups, bowls, jars and pitchers. The team closely examined 177 sherds found at archaeological sites throughout the Southwest of North America, carefully selected from different time periods to find out how consistent the use of caffeine was. Caffeine was found on 40 of the sherds.

The results revealed that two different types of caffeinated drinks were consumed, from two different types of plant, neither of which would be recognised as coffee. One was made from cacao, the basis for chocolate. The other was made from the leaves and twigs of a type of holly called yaupon holly.

Neither of these plants were native to the North American Southwest, though it's already known that there was trade between North America and Mesoamerica, where cacao grows. Yaupon holly is native to the Southeastern United States, where the Native Americans used it to make what is referred to in early historic accounts as "black drink."

Crown and her team hypothesise that the drinks weren't an everyday occurrence, unlike how we drink coffee today. Instead, they would have been drunk on special occasions, such as during rituals, or important meetings and for medicinal purpose. This would be consistent with importation patterns from Mesoamerica, where imported items such as living scarlet macaws, pyrite mirrors and copper bells were ritually significant, and were found at several sites that also had clay vessels with caffeine residue.

Yaupon holly is not necessarily made into a drink for the purposes of caffeination, either: historic documents and later research papers from the US Southeast describe men drinking large amounts of black drink, then throwing it all up in a sort of ritual cleansing.

The full paper, published in the journal PNAS, can be found online.