The presence of trace theobromine and caffeine in some ancient bowls indicates more than a delicious diet: It implies much greater exchange between North and Mesoamerica.

Pottery bowls from the American southwest that contained evidence of long-ago chocolate consumption (Peabody Museum of Archeology and Ethnology/Harvard University via Science)

Humans have been eating chocolate for a long time. The earliest evidence suggests that people living in the Chiapas region of Mexico might have consumed cacao as far back as 1900 BCE, and by the Classic Maya period (250-900 CE), the Maya were raising the beans and turning them into a spicy, frothy drink for Maya royalty and religious rituals. They also used the seeds as currency.

Although the plant had a place of pride in Mesoamerican society, it is not thought to have traveled very far north. Archaeologists have searched for connections between Mesoamerican people and those who were living in the American southwest and have found few.

Now, a new study published in the Journal of Archaeological Science suggests that there might have been more exchange than previously thought. Their evidence? Chocolate. Well, not chocolate exactly, but traces of theobromine and caffeine (two compounds found in cacao) in bowls from an eighth-century archaeological site in Alkali Ridge, Utah. That chocolate would have had to have been imported from Mesoamerican cacao orchards, thousands of miles away.

Not everyone is so sure. As Traci Watson of Science Magazine reports:

Other researchers, though tantalized, are also cautious, precisely because the new study and the authors' previous research have found so much chocolate. If cacao were so common, there would be stories or visual references or historical references to it, writes Ben Nelson, of Arizona State University, Tempe, who studies the ancient cultures of northern Mexico and the American Southwest, in an e-mail.

Archaeologist Michael Blake, who studies agriculture in the Americas, casts doubt on the paper's suggestion that Site 13 residents may have consumed chocolate as a source of nutrition, either at home or on the road. By the time cacao got to the American Southwest, it would've been "scarce, prized, and extremely valuable," writes Blake, of the University of British Columbia, Vancouver, in Canada, in an e-mail. "I may serve caviar and fine champagne at my daughter's wedding feast, but I'm not likely to pack it in my lunch bag when I go on a camping trip."

The study -- and the surrounding debate -- goes to show that chocolate consumption in North America isn't just a question of culinary intrigue, a quirky fact in the history of a beloved food. It's a clue that can help us fill out the mystery of the people who long ago lived on this continent. What they ate, how much they traveled and traded across cultures, who they were.