"The Jomon were not directly ancestral to Native Americans," lead author G. Richard Scott, professor of anthropology at the University of Reno, Nevada, and an expert in the study of human teeth, tells Live Science. "They [the Jomon] are more aligned with Southeast Asian and Pacific groups than with East Asian and Native American groups." Originally, scientists based their belief on stone tools, including arrowheads, found among both communities. This similar archaeological record dating back 15,000 years in Japan and North America was viewed as proof of the relationship between the two populations.