Excavations in 2015 at the site of Ru Diep in north-central Vietnam (Ha Tinh Province) raise significant questions about the transition into the Neolithic in this region, more than 5000 years ago. The material culture from the site reveals a mixture of both pre-Neolithic (Quynh Van culture) and Neolithic elements, in a shell mound context. The C14 dates for the site suggest that the surviving layers were deposited between outer limits of 3200 and 2900 cal. BC, but Bayesian analysis indicates a likely accumulation in less than 50 years. This date is almost one millennium older than expected for Neolithic-related materials in north-central Vietnam.