One theory holds that the people of Champa were descended from settlers who reached the Southeast Asian mainland from Borneo about the time of the Sa Huỳnh culture, though genetic evidence points to exchanges with India.[1]:317 Sa Huỳnh sites are rich in iron artifacts, by contrast with the Đông Sơn culture sites found in northern Vietnam and elsewhere in mainland Southeast Asia, where bronze artifacts are dominant. The Cham language is part of the Austronesian family. According to one study, Cham is related most closely to modern