Not everyone wants their teeth to be white and gleaming. Tooth blackening is a recognized part of modern Vietnamese culture, and a recent discovery hints that the roots of this practice may stretch all the way back to the Iron Age. During a recent archaeological expedition at the Dong Xa site in northern Vietnam, researchers found human teeth bearing the earliest known direct scientific evidence of intentional tooth blackening. The dating of organic materials discovered within a specific burial where the teeth were found traced them back 2,000 years.