The study, published in Science, focused on a gene known as MUC19, which is involved in the production of proteins that form saliva and mucosal barriers in the respiratory and digestive tracts. The researchers show that a variant of that gene derived from Denisovans, an enigmatic species of archaic humans, is present in modern Latin Americans with Indigenous American ancestry, as well as in DNA collected from individuals excavated at archeological sites across North and South America.