Denisovan hemimandible from 160,000-year-old Xiahe China fossil has 3-rooted lower second molar. 3-rooted lower molars occur in less than 3.5% of non-Asian Homo sapiens. 3-rooted lower molars exceed 40% in Asian-derived populations including China and New World. Fossil proves 3-rooted molar trait predates modern Homo sapiens dispersal. Trait links archaic Denisovans directly to recent Asian Homo sapiens lineages. Modern Asian dental morphology stems from Denisovan introgression. Non-Asians lack this archaic dental feature at high frequency.