Chocolate residues left on ancient jars mark cacao’s earliest known presence north of what is now the U.S.-Mexico border. The residues, found on pottery shards excavated from a large pueblo (called Pueblo Bonito) in Chaco Canyon in northwestern New Mexico, suggest the practice of drinking chocolate had traveled from what is now Mexico to the American Southwest by about 1,000 years ago. Scientists have known about the early uses of chocolate in Mesoamerica, with evidence for rituals involving liquid drinks made from cacao beans dating back more than 1,000 years. (Mesoamerica extends from central Mexico to Honduras and Nicaragua.) Chocolate debut Now, researchers think a similar ritual may have taken place in villages in Chaco Canyon. Patricia Crown of the University of New Mexico and Jeffrey Hurst of the Hershey Center for Health and Nutrition found traces of theobromine, which is in the Theobroma cacao plant that bears beans from which chocolate is made, on the shards. (The Hershey Center was established by the Hershey Company in 2006.) And Crown and Hurst suspect the shards came from cylinder jars, which measure an average of 10 inches tall (25 cm) and 4 inches (10 cm) wide. […]