As one of the most widely dispersed languages in this work, Austronesian languages mainly distribute in the islands but are very rare in the mainland region. Living in southern Vietnam, the Cham people represent the major Austronesian speakers in Mainland Southeast Asia (MSEA) and their origin is evidently associated with the Austronesian diffusion in MSEA. Hitherto, hypotheses stemming mainly from linguistic and cultural viewpoints on the origin of the Cham people remain a welter of controversies. Among the points of dissension is the muddled issue of whether the Cham people arose from demic or cultural diffusion from the Austronesians from Island Southeast Asia (ISEA). Addressing this issue also helps elucidate the dispersal mode of the Austronesian language.

Through the cooperation with Hanoi Medical University, researchers in State Key Laboratory of Genetic Resources and Evolution analyzed the mitochondrial DNA (mtDNA) variation of the Cham individuals collected from southern Vietnam. The results revealed that the Chams had a closer affinity with the Mon-Khmer populations in MSEA than with the Austronesian populations from ISEA. Further analyses failed to detect the potential homelands of the Chams in ISEA. Therefore, the results suggested that the origin of the Cham was likely a process of assimilation of massive local Mon-Khmer populations accompanied with language shift, thus indicating that the Austronesian diffusion in MSEA was mainly mediated by cultural diffusion, at least from the matrilineal genetic perspective, an observation in agreement with the hypothesis of the Nusantao Maritime Trading and Communication Networks.

The finding was published online at May 31 in Molecular Biology and Evolution (http://mbe.oxfordjournals.org/cgi/content/abstract/msq131).